You guys are killing me.

BOB DD

On Nov 20, 2006, at 5:11 AM, Harold Mandel wrote:

At the potential required to effect a change the resulting amperage might be
deleterious.

Why not e-mail Jennings to see their fix?

This could be interesting, Hal.

Hal
W4HBM

-----Original Message-----
From: ham_amplifiers@... [mailto:ham_amplifiers@...]
On Behalf Of Mike Sawyer
Sent: Monday, November 20, 2006 7:57 AM
To: ham_amplifiers@...
Subject: Re: [ham_amplifiers] Re: AC HiPot tester question

Now, let me ask a question of social and political importance: Is it
possible to 'remove' the whisker by introducing and hi(er)-voltage to the
vacuum cap? The reason I ask is that this was practice used to recover
Ni-Cad batteries. A whisker would develop between anode and cathode and a
charge capacitor, several times the actual output of the cell would be
placed across it, (reversed polarity if memory serves me), and physically
'burn' the offending whisker.
Mod-U-Lator,
Mike(y)
W3SLK
----- Original Message -----
From: craxd <mailto:craxd@...>
To: ham_amplifiers@...<mailto:ham_amplifiers@...>
Sent: Monday, November 20, 2006 12:29 AM
Subject: [ham_amplifiers] Re: AC HiPot tester question

It sounds to me that Jennings wants things two different ways. First
they say don't momentarily test a vacuum cap with DC, but it's okay
to put one in service as a DC blocking cap, de-rated or not. From
everything I've ever read, the whisker problem is caused over time,
not in one minute of use. A DC blocker cap could be in an amp for a
lifetime. That's a good sales gimmick to sell hipots though. I've
never seen that warning either by Comet, or by any of the Russian
manufactured caps. If the cause is over the copper being too soft
used for the plate cups, it ought to be changed to a hard copper or
an alloy to stop it. I can see soft copper for the bellows, but not
the plate cups.

Thank God Rich and I didn't question the Jennings engineers on the
other list as we would have been sent another e-mail by the unknown
admin chastizing us for ever questioning these professionals with
published papers, etc....

Best,

Will

--- In ham_amplifiers@...
<mailto:ham_amplifiers%40yahoogroups.com> , R L Measures <r@...> wrote:

On Nov 19, 2006, at 2:59 AM, pentalab wrote:

--- In ham_amplifiers@...

<mailto:ham_amplifiers%40yahoogroups.com> , R L Measures <r@...> wrote:

...
RICH SEZ.... A 20kV rated C to block 7000V DC sounds like over-

engineering since the actual AC potential across the blocker is
minimal.

#### Rich... Jenning's engineers tell me when using either fixed
glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of the
FIXED vac cap has to be a MINIMUM of 3 X No load plate V......
other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

So why does the statement I quoted in the Jennings catalog on p.4
about DC operation state otherwise?

### Ur gonna get "whisker's" anyway in plate block service for
a fixed vac cap.... so the 20 kv cap... will actually be over
time... a lot lower than 20 kv. IF u Hi-pot test a fixed vac cap
that has been used for plate block service.... u will see it no
longer hi pot tests to 20+ kv any more.

### other than 11m ops... I never see fixed vac caps used as plate
blockers.

I do, Jim. Even 500pF is plenty for a DC blocker at 1.8MHz (XC =

190-

ohms) in typical amplifiers since RL is in the kilo-ohms range.

11m ops don't need much C for 11m... 100-250 pf max
is what they typ use. Their requirements are for a plate block cap
that handles LOTS of RF... esp for 4x20's, etc.

Tom Rauch apparently knows a Ham who mistakenly used a 100pF DC
blocker in a homebrew amplifier. The amplifier produced the

expected

output from 1.8 to 28 MHz. Sometime later, when a friend was

being

shown the amplifier, he noticed that there were only twp zeros

after

the 1 on the blocker cap. When a 1000pF cap was substituted for

the

100pF cap, the output did not increase although the tuning changed
slightly on the 1.8MHz band.
...
R L Measures, AG6K, 805.386.3734
r@... <mailto:r%40somis.org> , rlm@..., www.somis.org

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Nov 20, 2006, at 4:56 AM, Mike Sawyer wrote:

Now, let me ask a question of social and political importance: Is it possible to 'remove' the whisker by introducing and hi(er)- voltage to the vacuum cap?

I have done this, Mike, but one must be careful not to overdo the procedure.
To begin with, connect a 20M to 100M HV-rated resistor in series with the high-potential tester to seriously limit current. . . When a vacuum-C has been in storage for a long time, it is not unusual to find that as applied potential rises, it will "tink" (indicating a flashover) briefly discharging the cap several kV below its rated peak-V. This does not mean that the cap is feculent. By slowing raising the applied potential until the cap tinks, Cu whiskers can be burned off, raising the cap's piv each time the procedure is repeated. However, at some point in the tinling procedure, the piv will begin to DEcrease -- i. e., the procedure becomes destructive rather than constructive. IOW, this is yet another case where mo' is Not always mo' betta. It is my opinion the 3 or 4 tinks is about the limit.
cheerz

...
Mike(y)
W3SLK
----- Original Message -----
From: craxd
To: ham_amplifiers@...
Sent: Monday, November 20, 2006 12:29 AM
Subject: [ham_amplifiers] Re: AC HiPot tester question

It sounds to me that Jennings wants things two different ways. First
they say don't momentarily test a vacuum cap with DC, but it's okay
to put one in service as a DC blocking cap, de-rated or not. From
everything I've ever read, the whisker problem is caused over time,
not in one minute of use. A DC blocker cap could be in an amp for a
lifetime. That's a good sales gimmick to sell hipots though. I've
never seen that warning either by Comet, or by any of the Russian
manufactured caps. If the cause is over the copper being too soft
used for the plate cups, it ought to be changed to a hard copper or
an alloy to stop it. I can see soft copper for the bellows, but not
the plate cups.

Thank God Rich and I didn't question the Jennings engineers on the
other list as we would have been sent another e-mail by the unknown
admin chastizing us for ever questioning these professionals with
published papers, etc....

Best,

Will

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 19, 2006, at 2:59 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

...
RICH SEZ.... A 20kV rated C to block 7000V DC sounds like over-

engineering since the actual AC potential across the blocker is
minimal.

#### Rich... Jenning's engineers tell me when using either fixed
glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of the
FIXED vac cap has to be a MINIMUM of 3 X No load plate V......
other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

So why does the statement I quoted in the Jennings catalog on p.4
about DC operation state otherwise?

### Ur gonna get "whisker's" anyway in plate block service for
a fixed vac cap.... so the 20 kv cap... will actually be over
time... a lot lower than 20 kv. IF u Hi-pot test a fixed vac cap
that has been used for plate block service.... u will see it no
longer hi pot tests to 20+ kv any more.

### other than 11m ops... I never see fixed vac caps used as plate
blockers.

I do, Jim. Even 500pF is plenty for a DC blocker at 1.8MHz (XC =

190-

ohms) in typical amplifiers since RL is in the kilo-ohms range.

11m ops don't need much C for 11m... 100-250 pf max
is what they typ use. Their requirements are for a plate block cap
that handles LOTS of RF... esp for 4x20's, etc.

Tom Rauch apparently knows a Ham who mistakenly used a 100pF DC
blocker in a homebrew amplifier. The amplifier produced the

expected

output from 1.8 to 28 MHz. Sometime later, when a friend was

being

shown the amplifier, he noticed that there were only twp zeros

after

the 1 on the blocker cap. When a 1000pF cap was substituted for

the

100pF cap, the output did not increase although the tuning changed
slightly on the 1.8MHz band.
...
R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Nov 19, 2006, at 10:04 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 19, 2006, at 7:32 AM, pentalab wrote:

--- In ham_amplifiers@..., Tony King - W4ZT <w4zt-
060920@> wrote:

Which MOV's do you use and where do you get them?

### From Mouser... Digi key has em as well... aprx 2" tall x
1/2" thick x 2.75" wide base. Those are the 130 v units.
The closest ones for the 240 V service are 250 V rated. IMO..
250 V rated Mov's are cutting it too close.

RICH SEZ...Perhaps it might be a good idea to read the specs on

the 250v-rated MOV's, Jim.

### I did. And the 250 v rating is for a 250 V max rms CCS
condition.

The critical thing is: at what potential does the unit begin to conduct current.

Depending on who makes a MOV.... clamp V is always
way higher than that.... which is why old books always said to use
twice the PIV needed for a FWB. These days it's triple the PIV
needed [at least for commercial recifier assys].

In the 8169 / Plywood Box #2 amplifier, I deliberately used a HV rectifier safety factor of 33% based on my measurement of the actual PIV. There has never been a failure.

### MOV's are just a series of "grains" inside. The series
grains will start to short out with successive hits from
transients, spikes, surges, etc. The actual V rating of the MOV
will slowly start to go down. That's why 130V rated MOV's
are normally used. A 250 v rated Mov is cutting it too fine
for folks whose line V can reach 247-250 V.

You seem to assume that conduction for a 250v rating begins at 251 x 1.14 volts. It does not.

A few too many
hits on the MOV.. and it's continuous V rating will drop to the
point where it will conduct.... and short out. UNLESS it's
fused.... it's gonna burn up... or explode.

Be there, done that. 1000J is pretty nasty.

Way too many house
fires caused by MOV's as is.

### Check out Joslyn's website in the USA. They are the number
one maker of commercial MOV assemblies for use in commercial /
industrial environments. You won't see any 250 v rated MOV's
used on any 240 V circuits.

chortle. My guess is that Joslyn has yet to try measuring the zener- v of a 250V rated MOV.

...

later

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Nov 20, 2006, at 2:34 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

The point here is.... by oversizing the HV fuse.... the load is
then transfered to the 100 A breaker in the 240 v main 200 A
panel.... which of course didn't blow open...... instead the
glitch R's fried themselves... !
You need well over 100 A to open a 100 A panel breaker.

RICH SEZ... Which is why I used a 40A thermal-magnetic breaker for

the 8170 amp.

#### Which will be on the ragged edge of opening...

Precisely, but so far never has.

since we
already determined you are sucking 110 A on keydown cxr.

We? YOU assumed that I was stupid enough to do this.

Would
be kind of nice to run a dead cxr..for at least 3-7 seconds.. just
to take steady state plate/grid current readings. You can't do
that with a 40 A breaker. With a 2 x pole [50 A per pole]
breaker.. with it's poles wired in parallel.. and tie bar removed...
and 2 x such assys' used... one per hot leg... u can then have all
4 poles activated for dead cxr stuff... and kick one pole off
per breaker... for ragged edge ssb operation. IE: toggle from
a 100 A breaker... down to a 50 A breaker.

BTW... that Dahl A-540 hypersil C core 253 lb plate xfmr I
have... has a .01 ohm primary.

RICH SEZ...How did you measure this?

### with a B+K 875-B... also used a HP DVM [very expensive
box... just back from the cal lab, reads some extra zero's] The
Fluke 87 will only read to 1/10ths of an ohm. Also, low
resistance readings can be even more accurately done using mho's/
siemens. .01 ohm = 100 mho's. .001 ohm = 1000 mho's .0001
ohm = 10,000 mho's. I have gear that will read higher than
10,000 mho's. In all cases... the sec was shorted, when
taking pri readings... and vice versa.. when taking sec readings.

A 1 significant digit reading does not imply great gobs of accuracy. I measure low resistances by putting 1.000A through them and measuring the mV drop with my Fluke DMM.

RICH SEZ... Thus, my guess is that the short-circuit current
would be c. 470A-rms. The secondary current under a short would
be 470A / 21.6 = 21.7A-rms.

Jim: Why would a HV fuse in the secondary be better than a

250V fuse in the primary?

### Cuz a 3 A sandfilled fuse.. with 8 kv/50 ohm glitch = 160
A of fault current. 160A of fault current has a tendency to
blow a HV sand fuse in < 2 msecs.

The glitch R begins to limit fault current in no time, and it's peak current that does the damage.

...

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Nov 20, 2006, at 12:17 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

...

RICH SEZ.... A 20kV rated C to block 7000V DC sounds like

over-

engineering since the actual AC potential across the blocker

is

minimal.

####### The AC potential across the cap has nothing to do with
it.

#### Rich... Jenning's engineers tell me when using either

fixed

glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of

the

FIXED vac cap has to be a MINIMUM of 3 X No load plate

V......

other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

RICH SEZ... So why does the statement I quoted in the Jennings

catalog on p.4 about DC operation state otherwise?

#### Dunno. Eimac sez the same thing, de -rate vac caps to
1/3 for plate block use !

RICH SEZ.... I did not read this in any Eimac literature,

#### You don't have friends at Eimac... like me.

.. and Tom Rauch?

RICH SEZ...and it does not make good sense

### sure it does. Apply continuous DC HV to a vac cap.,. and
eventually... DCV rating.. due to whisker growth...

I have seen whisker growth in vacuum caps that have been in long-term storage. However, when such caps are high-potted, after a few tinks the stickers apparently burn off and the piv capability returns.

DROPS...hence size the caps DC HV rating at least 3 x the plate
supply's unloaded v to start with. That's what Jenning's sez...

So why does the Jennings Vacuum and Gas Capacitor catalog say on p.6:
"DC -- Vacuum capacitors should not be operated in DC applications above the peak RF working voltage."
"DC Plus RF -- For DC plus RF applications, the sum of the DC plus the peak RF voltage should not exceed the peak RF working voltage."

that's what Eimac sez... that's what 11m ops say... or else it's
flash kablamo time ..... end of story.

hardly. Page 6 still has you by the short hair.

RICH SEZ...since the prima facie consideration for a DC blocker is
the current rating at 29MHz - since at 10m, the DC blocker
typically carries c. 90% of the tank's RF circulating current.

#### "prima facie consideration" ? Are you OJ's lawyer too ?

Johnny's dead, I'm not quite there yet - despite the plenitude of fervent prayers of Mormons, Muslims, Jehovah's Witnesses, SDAs, and Roman Catholics. .

- prima facie - adv.
1. At first sight; before closer inspection: They had, prima facie, a legitimate complaint.

### yes... 10m and above is the worst case scenario for a plate
block cap.... that's what I have been saying all along.

The 11m ops also highly agree. The
11m ops tell me if they try and use a 16 kv test rated fixed vac
cap with 10.5 kv dc on it..... it will eventually arc.

RICH SEZ... Probably true since Jennings advises that 60% of the DC

test V is the max WV when using DC + RF.

### what ? Jenning's sez the max AC RF working V is 60%
of the DC test V.

Page 6. The Vacuum and Gas Capacitor Catalog:
"RF Working Voltage is the maximum RF voltage that can be applied to the capacitor without affecting its ability to withstand instantaneous overloads, It is generally 60% of the Peak Test Voltage rating. ..."

They are asuming and also implying you have
employed a plate block cap already.

Staying below the peak RF WV ability is the prime concern no matter the application.

What they are refering too is
using a vac cap as a C1/C2 tune/load cap... or using a vac cap to
pad a tune/load cap. In any event... the AC voltage across a
plate block cap is so low... u can ignore it.... UNLESS you insist
on using really small value plate block caps... then you end up
with high AC voltages across em.... as in plate current X Xc
of plate block cap.

Agreed

### for 10.5 kv dc no load... you want at least a 25-30 kv test v
rated fixed vac cap.

According to page 6,

"DC Plus RF -- For DC plus RF applications, the sum of the DC plus the peak RF voltage should not exceed the peak RF working voltage."

Example -- A 1000pF DC blocker, using an 8281 running at 10.5kV with a typical tank Q, would have c. 20A of tank circulating current flowing through the DC blocker at 29MHz, so there would be c. 105volts drop across it. Thus, according to p.6, a capacitor with 10,500v plus 105v = 10,605 / 0.60, so a 17,500 DC-test V or higher unit should be used. However, amplifiers with 10,500v anode supplies are not all that common in Hamdom. Also, 10,500v is getting pretty close to the land of x-rays.

...

RICH SEZ... I do, Jim. Even 500pF is plenty for a DC blocker at

1.8MHz (XC = 190- ohms) in typical amplifiers since RL is in the
kilo-ohmS range.

#### No way. 500pf = 176 ohms of XC.

RICH SEZ.... The rule of thumb is a 5 to one ratio for a coupling

reactance. 176- ohms of XC and a RL of 176-ohms x 5 = 880-ohms or
higher RL should be okay.

### No way. Where did u cook up this 5 to one ratio ??? Not
in any of my engineering books. Any big metal tube operating
with a 880 ohm plate load Z... is gonna be sucking loads of plate
current. 4-5 A typ. 5 A x 176 ohms XC = 880 vac You just
lost it right there!

#### 100 pf = 884 ohms XC [1.8 mhz] gimme a break !

RICH SEZ... With a pair of 3-500Zs, RL is c. 2k, so 884-ohms would

probably work okay if the Tune-C could tune it out.

#### Now it gets even worse ! 5 A x 884 ohms = 4400 vac dropped
across the plate block cap..

Where did the 1.5A come from?

...

### a 100 pf plate block doorknob cap wouldn't last 30 seconds

in a 3x3

RICH SEZ... Why would the capacitor dissipate heat?

#### lemme see. With say 2.5 A of plate current at 5 kv under
load... and on 29 mhz... current through the 100 pf plate block
cap = 32 A.

How did you calculate this, Jim?

A HT-57 100 pf cap is only rated at 13.7 A @
30 mhz [with 13.7 A, the 100 pf cap's temp is 55-65 deg C...149
deg F..... and well over 100+ deg C.. with 32 A flowing through
it] Use multiple metal tubes on 10m or bigger single metal
tubes with lots of anode to chassis C..... look out.

### with 32 A through a cap rated for 13.7 A = meltdown. [5.5 x
more heat. 32/13.7= 2.34 2.34 squared = 5.5 more trbl] Don't
gimme this nonsense about pulse tuning and SSB being a 15% duty
cycle. The correct component here is 6 x 500 pf HT-57's... or
3-4 x 200pf HT-57's. I use 6 x 500 pf HT-57's.... then it
will have low XC on 160m too.

Later... Jim VE7RF

to be continued ...


R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

At the potential required to effect a change the resulting amperage might be
deleterious.

Why not e-mail Jennings to see their fix?

Hal
W4HBM

开云体育

On Nov 19, 2006, at 10:28 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

RICH SEZ... I did the calculations for the 8170 amplifier with

Ohm's Law. The calc. peak mains current was c. 300A. The
measured result was 1200v- pk into 50-ohms on SSB.

### 1200 V pk equates to 14,396 watts pep output into a 50 ohm
load..

Correct

..14,395.65 /.63 = 22,850 w dc input.

My guess is that the efficiency was closer to 60%.

Primary VA = 22,850
x 1.22 = 27,877 va 27,877 /240v = 116.155 A

Only if one assumes that the filter-C stores zero Joules in the 70%
interim between 30pps, 30% duty-cycle tuning pulses. .

.... not
including fil xfmr, blower etc. Peak current is aprx 375A
with big wire and a big C filter... every 8.3 msecs.

The mains ESR was measured at 0.079Ω, add 200' of #4 Cu. Xfmr pri. R
= 0.075Ω, sec R = 12Ω, and the turns ratio is 240/3000 = 12.5. I
came up c. 300A-pk - which could have been in the ballpark since my
wife could hear the wires vibrate in the attic when I tuned the
sucker up.

### Rich... tell us how you take a steady state plate meter
readings and grid current.

For designed-for-SSB amplifiers, I don't. The plate/anode current
meter is used only to adj. ZSAC. During speech, it probably indicated
c. 1/3 of the anode current, or perhaps 1.3 A. . . After adjusting
for zero grid-current and 0.5A of ZSAC, and tuning-loading for the
specified screen-current I was done with meter readings. The next
step was optional -- to measure peak-V into 50-ohms with an
oscilloscope and a HV multiplier probe.

.... with out blowing ur under rated 40 A
house breaker ???? IE: a dead cxr... for just 3-6
seconds... just long enough to measure grid/plate current + fil V,
loaded plate V, etc. Forget the fil v/ plate v...... focus on
just the plate + grid current.

With an amplifier that was designed for SSB-only, only a dead-head
would use a dead-carrier.

### If u just pulse tune it...and talk...fine... I do too. Unless
both ur plate/grid meter's are peak reading types.... I can't see
how it's done.

Easy: grid current is zero, ZSAC is whatever is specified, with a
30% duty-cycle tuning-pulser, multiply the screen-current reading by
3.3. For example, normal screen-current is 120ma, so when the meter
peaks at 36mA with the Tune-C control, the 8170 or 8171 is ready for
use.

### IMO.. the entire system should be configured to at least
handle a 4-7 second dead cxr.... without blowing breakers,
melting coax, frying tank coils etc.

To have been able to go on the A0 trip would have required a HV
transformer that weighed and cost triple, plus the added cost of 200'
of #2 Cu.
The total cost for the Plywood Box 8170 project was $1200, not
counting the 200' of #4 Cu for the 240v 50a outlet.

### For a 8170/8171.... I'd use a 100A breaker... and a bare min
of 2 ga wire... and considering the 300-400A peak current draw
every 8.3 msec..... 3 x 000 CU is the real ticket.... regardless
of length.

For RTTY, this makes sense, but for SSB, it's greenbacks flushed down
the crapper.

### BTW... what's the CCS rating of the SB-220's plate
xfmr ??? I heard it was 1200 va.

It's not speced, Jim, but the core dimensions figure out to c. 550w.

Now Rich has stated it's only
600Va. I'm sure the smaller SB-200 is 600 va CCS.

### Will a SB-220 stock... in good condition, on low plate
V...be capable of delivering 600W CCS RTTY ???

I have no idea, Jim. Continuous broadcasting is something I have zero
interest in.

later

...

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

The point here is.... by oversizing the HV fuse.... the load is
then transfered to the 100 A breaker in the 240 v main 200 A
panel.... which of course didn't blow open...... instead the
glitch R's fried themselves... !
You need well over 100 A to open a 100 A panel breaker.

RICH SEZ... Which is why I used a 40A thermal-magnetic breaker for

the 8170 amp.

#### Which will be on the ragged edge of opening... since we
already determined you are sucking 110 A on keydown cxr. Would
be kind of nice to run a dead cxr..for at least 3-7 seconds.. just
to take steady state plate/grid current readings. You can't do
that with a 40 A breaker. With a 2 x pole [50 A per pole]
breaker.. with it's poles wired in parallel.. and tie bar removed...
and 2 x such assys' used... one per hot leg... u can then have all
4 poles activated for dead cxr stuff... and kick one pole off
per breaker... for ragged edge ssb operation. IE: toggle from
a 100 A breaker... down to a 50 A breaker.

BTW... that Dahl A-540 hypersil C core 253 lb plate xfmr I
have... has a .01 ohm primary.

RICH SEZ...How did you measure this?

### with a B+K 875-B... also used a HP DVM [very expensive
box... just back from the cal lab, reads some extra zero's] The
Fluke 87 will only read to 1/10ths of an ohm. Also, low
resistance readings can be even more accurately done using mho's/
siemens. .01 ohm = 100 mho's. .001 ohm = 1000 mho's .0001
ohm = 10,000 mho's. I have gear that will read higher than
10,000 mho's. In all cases... the sec was shorted, when
taking pri readings... and vice versa.. when taking sec readings.


RICH SEZ... Thus, my guess is that the short-circuit current
would be c. 470A-rms. The secondary current under a short would
be 470A / 21.6 = 21.7A-rms.

Jim: Why would a HV fuse in the secondary be better than a

250V fuse in the primary?

### Cuz a 3 A sandfilled fuse.. with 8 kv/50 ohm glitch = 160
A of fault current. 160A of fault current has a tendency to
blow a HV sand fuse in < 2 msecs. Fast 100 A fuses in the
primary would work... but with 470 A... would not open as fast.
Only 1 x HV fuse needed..... VS TWO x 100 A high speed fuses
in 240 v primary.

.... LOADS... as my buddy with the same 253 lb xfmr
just found out. 253 lb xfmr with a core good for 20 KVA
CCS with a 100 A slo breaker... vs lowly glitch R [wound with
nichrome wire no less] .... no contest.... glitch loses every
time........ unless a correct sized HV fuse is used !

RICH SEZ.... When a correct size HV fuse is used and a short is

applied, does the glitch R survive?

### sure. Doesn't even put a dent on the Glitch R. You can
crowbar the thing all day long.

#### We did find out where the HV arc was happening.... was
between OUTPUT of parasitic suppressor globar clip.. and the 20-
17-15m 1/2" tubing tank coil... bad arc. When driven... the
anode V rises to almost double [restored tank sine wave back
feeds through plate block caps to anode.. adds to the existing dc
HV.] Fix was to rotate the coil on it's axis a bit.

## Last time... the arcing was caused by LOOSE strap from C1
vac tune cap to 20-17-15 m tank coil. STRAP had flopped over a
bit.... and arc occured between parasitic suppressor coil and
this loose strap. Of course in both cases.. ALL the tank
components are at chassis grnd... including tune/load
caps/bandswitch/ both tank coils, etc.... due to the HB 45 uh 18
ga solenoid wound safety choke... wired between chassis and hot
side of vac LOAD cap. [45 uh choke wound on 1" diam solid Teflon
rod... bullet proof... also identical to the 45 uh RF choke used in
the 2 x piece plate choke set up 135/180 uh + 45 uh]

### This safety RF choke HAS to be rugged... no place for your
ARRL hand book 2.5 mh 30 ohm 36 ga.... pi wound assy. Those
things will blow into a million pieces when you try and stuff 160
A through em. They also have more than a tendency to blow up..
with NO HV fuse.... and also with no glitch R.... well... use ur
imagination... 8 kv / 1.4 ohms ESR from modern day lytics + plate
choke = 5700 A Actually.. it's not that bad... since the DC
resistance of any floozy RF safety choke will limit current...
then the choke explodes. A 45 uh 18 ga safety choke is
compact... and a snap to make. Drill + tap a 1/4-20 thread into
the base... and it's easy to mount. 2 x Transverse brass threads
terminate the 18 ga magnet wire.

Later... Jim VE7RF

later... Jim VE7RF

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

--- In ham_amplifiers@..., "Robert B. Bonner"
<rbonner@...> wrote:

Guys,

My first job out of my undergrad program was with a building

automation (energy) company. We installed PFC caps on buildings
all over the place.

For the Super Big guns that are running 100 AMP primarys with

three phase power supplies doing PFC will just make the power to
the primary smoother and your power company happier. I don't think
it is worth the expense for correction caps. Either way I would
install them on the amplifier not the building.

### On HV supplies with resonant choke filters.... they all have
a better power factor... compared to a simple C input filter.
When you increase the C in a C filter HC supply... the power
factor gets WORSE. Sounds to me like this 90 deg lag is not a
fixed thing... but vary's... depending on power factor itself...
IE: .8 pf vs .9pf vs .98pf

### Since a simple C input filter has a WORSE PF than a resonant
choke filter.... my electrician buddy is suggesting the huge C is
responsible for the worsening pf.... and NOT the XL of either
the pri/sec of the plate xfmr. If that's the case... Dahl is
probably right, he should know. Dahl is telling me on a large C
input filter, that you can't use PF correction caps on the pri
of the plate xfmr. It just makes the PF worse still... and
magnetizing current increases. Since the C filter on the output
side is responsable for the lousy PF on a C input filter... probably
what's needed is a choke.. or XL across the plate xfmr pri.... or
perhaps in series with the plate cfmr pri ??

### Even if it could be done... the load is not constant on the HV
supply... it's nil [except for magnetizing current and bleeder] on
RX.... and vary's on TX from ZSAC... to full bore. Any
compensation would probably have to be relay switched out on RX...
and optimized for an average load on TX... on ssb anyway.

BOB DD


WILL SEZ... I looked through about every book I have on

transformers and power supplies, and never found anything about
using a cap for power factor correction. There's plenty about using
a cap with an AC motor, but nothing about transformers. The
Standard Handbook For Electrical Engineers only show adding them to
motor circuits or circuits feeding motor loads. Nothing under the
transformer section.

### That's what I suspected. I don't see any PFC caps on SW
broadcast TX either... not at 1st glance anyway. None of them are
using C input filters I believe.... might be wrong. With 3 phase
HV... ripple is only 4.8 % b4 any filtering. A simple C input
filter would reduce the ripple to zip. However a resonant
choke would do the same thing.. and have a better power factor at
the same time. For 24/7 operation.. and huge power... any
savings would add up.

WILL SEZ... The only way to cut back on magnetizing current is to

use more iron in the core lowering its flux density. The more iron
for the same amount of turns, the current drops. I researched
magnetizing current in C-core Hipersil (or M-6) transformers some
time back, and seen they had a good bit more magnetizing current
than most EI cores using M-19 steel. The reason being is they run
Hipersil from 15 to 17 kilogauss. M-19 and M-22 are ran from 14 to
10 kilogauss. Over 15 kilogauss in Hipersil, the current really
shoots up. The way to cure this is to have a transformer wound with
the same number of turns, but with a larger core area in either a C-
core or an EI core. One would have to tell the winder to use a
lower flux density of say 12 to 10 kilogauss using a C-core with
Hipersil or M-6 for a low magnetizing current. M-19 for an EI core
may be a better choice if available as it will be a good bit
cheaper. The core loss isn't much greater than M-6 either.

### I'm gonna ask Dahl what kind of hypersil he uses. The 120
lb 10 kva hypersil pole pig I have has 1.9 A of magnetizing
current at all times. The 253 lb Dahl hypersil has only 1.6
A of magnetizing current [it's a 3 A CCS sec = 15.5 kva CCS] I
was expecting a LOT more magnetizing current from the 253 lb
xfmr. [esp since it's double the weight of my pole pig]. The
1.6 x 240v = 384 Va of magnetizing va is small... compared to the
4.5 A int load you can pull off the sec. Still.. that's 384-va
on RX all the time.

### BTW... it's 384 va... whether FWB/caps/bleeder connected...
OR disconnected.. makes no difference.... even when sucking 100
w of bleeder diss. Ditto with pole pig supply.

### Dahl tells me the A-540 core he uses on all the 253 lb'ers is
good for 20 KVA CCS. Once u get a sec over 4 kv... the CCS I
rating drops from 4 A... down to 3 A. At 7.5 kv sec... it's
then down to 2.5 A CCS. My xfmr [due to wire ga on sec] is
rated at 15.5 kva..... however the core itself is good for 20 kva.

later... Jim VE7RF

Best,

Will





Yahoo! Groups Links

craxd wrote:

The boards are okay I guess but there is nothing special about the current trips. All they do is sense a voltage drop across a resistor with higher current and trigger an opto-couplers LED with it. This is turn will open a circuit by a relay or transistor circuit.

What you say here is true, Will. Each individual circuit is simple. The major benefit to the boards is that you can buy one that has the circuits designed and ready to go. Not only that, but the trips are linked together to provide fault lines, both hard and soft, which can save more than just a little trouble fixing something. Ian and Paul both make good boards. My personal favorite is Paul's. He uses multi turn pots and the 26V supply is on board including the power transformer for it and the bias regulator circuit is there too. This not only eliminates the need for you to provide another supply but also provides the juice for the t/r and control relays as well. You can also implement as much or as little of it as you like.

Another thing I seen in one board is that they sample a little of the screen or bias voltage and put that into a regulator to get the control voltage for a relay, etc. That was done to keep from having another coil on the transformer for low voltage. However, you need one anyhow for the antenna relay, and others.

I haven't seen that.

I design my own as to me any of the boards I've seen are a little over-kill and over complicated for my taste. The more components placed in any circuit raises the likelyhood of failure in the future expotentially. I can make just as good of a regulator circuit with a few transistors and zener diodes. This for either a series pass or shunt regulator.
Best,
Will

<snip>
If you want cheap and easy, a simple design on proto board is fine for just the things you want. That's why I put together a simple bias board based on the same circuit commonly used with the TL431 reference to use as a retrofit bias board <>. Not everyone wants a complex system and not everyone appreciates the protection that you can have by using one of the control boards. It's just a personal choice and nice that we have those options today. My personal choice for home brew is to include the protection... Wouldn't build without it. For a retrofit, it usually isn't that practical or economical to do.

Besides the trip circuits used on the control boards there have been several older commercial amps like the B&W PT2500 that included a grid trip circuit. It isn't all that difficult to build and use.

I find the three lead regulators much more reliable than any series regulator built with a few transistors and zeners. They have over current protection and are so much simpler to use.


Regards, Tony

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

...

RICH SEZ.... A 20kV rated C to block 7000V DC sounds like

over-

engineering since the actual AC potential across the blocker

is

minimal.

####### The AC potential across the cap has nothing to do with
it.

#### Rich... Jenning's engineers tell me when using either

fixed

glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of

the

FIXED vac cap has to be a MINIMUM of 3 X No load plate

V......

other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

RICH SEZ... So why does the statement I quoted in the Jennings

catalog on p.4 about DC operation state otherwise?

#### Dunno. Eimac sez the same thing, de -rate vac caps to
1/3 for plate block use !

RICH SEZ.... I did not read this in any Eimac literature,

#### You don't have friends at Eimac... like me.




RICH SEZ...and it does not make good sense

### sure it does. Apply continuous DC HV to a vac cap.,. and
eventually... DCV rating.. due to whisker growth...
DROPS...hence size the caps DC HV rating at least 3 x the plate
supply's unloaded v to start with. That's what Jenning's sez...
that's what Eimac sez... that's what 11m ops say... or else it's
flash kablamo time ..... end of story.






RICH SEZ...since the prima facie consideration for a DC blocker is
the current rating at 29MHz - since at 10m, the DC blocker
typically carries c. 90% of the tank's RF circulating current.

#### "prima facie consideration" ? Are you OJ's lawyer too ?

### yes... 10m and above is the worst case scenario for a plate
block cap.... that's what I have been saying all along.

The 11m ops also highly agree. The
11m ops tell me if they try and use a 16 kv test rated fixed vac
cap with 10.5 kv dc on it..... it will eventually arc.

RICH SEZ... Probably true since Jennings advises that 60% of the DC

test V is the max WV when using DC + RF.

### what ? Jenning's sez the max AC RF working V is 60%
of the DC test V. They are asuming and also implying you have
employed a plate block cap already. What they are refering too is
using a vac cap as a C1/C2 tune/load cap... or using a vac cap to
pad a tune/load cap. In any event... the AC voltage across a
plate block cap is so low... u can ignore it.... UNLESS you insist
on using really small value plate block caps... then you end up
with high AC voltages across em.... as in plate current X Xc
of plate block cap.

### for 10.5 kv dc no load... you want at least a 25-30 kv test v
rated fixed vac cap.

...

RICH SEZ... I do, Jim. Even 500pF is plenty for a DC blocker at

1.8MHz (XC = 190- ohms) in typical amplifiers since RL is in the
kilo-ohmS range.

#### No way. 500pf = 176 ohms of XC.

RICH SEZ.... The rule of thumb is a 5 to one ratio for a coupling

reactance. 176- ohms of XC and a RL of 176-ohms x 5 = 880-ohms or
higher RL should be okay.

### No way. Where did u cook up this 5 to one ratio ??? Not
in any of my engineering books. Any big metal tube operating
with a 880 ohm plate load Z... is gonna be sucking loads of plate
current. 4-5 A typ. 5 A x 176 ohms XC = 880 vac You just
lost it right there!

#### 100 pf = 884 ohms XC [1.8 mhz] gimme a break !

RICH SEZ... With a pair of 3-500Zs, RL is c. 2k, so 884-ohms would

probably work okay if the Tune-C could tune it out.

#### Now it gets even worse ! 5 A x 884 ohms = 4400 vac dropped
across the plate block cap........ not to mention the 45-63A of RF
flowing through it ..on 10m ! [using a 100 pf plate block cap +
big metal tubes]

### Stick a single 100 pf HT-50/58 cap in any 1500W amp....
run it at 1500 W RTTY/FM on 1.8 mhz for say 20 mins.... and
let us know what happens.

RICH SEZ... > no

#### It would vaporize.... that's why.

### a 100 pf plate block doorknob cap wouldn't last 30 seconds

in a 3x3

RICH SEZ... Why would the capacitor dissipate heat?

#### lemme see. With say 2.5 A of plate current at 5 kv under
load... and on 29 mhz... current through the 100 pf plate block
cap = 32 A. A HT-57 100 pf cap is only rated at 13.7 A @
30 mhz [with 13.7 A, the 100 pf cap's temp is 55-65 deg C...149
deg F..... and well over 100+ deg C.. with 32 A flowing through
it] Use multiple metal tubes on 10m or bigger single metal
tubes with lots of anode to chassis C..... look out.

### with 32 A through a cap rated for 13.7 A = meltdown. [5.5 x
more heat. 32/13.7= 2.34 2.34 squared = 5.5 more trbl] Don't
gimme this nonsense about pulse tuning and SSB being a 15% duty
cycle. The correct component here is 6 x 500 pf HT-57's... or
3-4 x 200pf HT-57's. I use 6 x 500 pf HT-57's.... then it
will have low XC on 160m too.

Later... Jim VE7RF

...
R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

RICH SEZ... I did the calculations for the 8170 amplifier with

Ohm's Law. The calc. peak mains current was c. 300A. The
measured result was 1200v- pk into 50-ohms on SSB.

### 1200 V pk equates to 14,396 watts pep output into a 50 ohm
load....14,395.65 /.63 = 22,850 w dc input. Primary VA = 22,850
x 1.22 = 27,877 va 27,877 /240v = 116.155 A .... not
including fil xfmr, blower etc. Peak current is aprx 375A
with big wire and a big C filter... every 8.3 msecs.

### Rich... tell us how you take a steady state plate and grid
current meter readings..... with out blowing ur under rated 40 A
house breaker ???? IE: a dead cxr... for just 3-6
seconds... just long enough to measure grid/plate current + fil V,
loaded plate V, etc. Forget the fil v/ plate v...... focus on
just the plate + grid current.

### If u just pulse tune it...and talk...fine... I do too. Unless
both ur plate/grid meter's are peak reading types.... I can't see
how it's done.

### IMO.. the entire system should be configured to at least
handle a 4-7 second dead cxr.... without blowing breakers,
melting coax, frying tank coils etc.

### For a 8170/8171.... I'd use a 100A breaker... and a bare min
of 2 ga wire... and considering the 300-400A peak current draw
every 8.3 msec..... 3 x 000 CU is the real ticket.... regardless
of length.

### BTW... what's the CCS rating of the SB-220's plate
xfmr ??? I heard it was 1200 va. Now Rich has stated it's only
600Va. I'm sure the smaller SB-200 is 600 va CCS.

### Will a SB-220 stock... in good condition, on low plate
V...be capable of delivering 600W CCS RTTY ??? If so...
the plate xfmr would have to be a 1200 va unit.

Later... Jim VE7RF

#### 3/000 CU from main 200A panel to HV supply is what's
really needed. Snip a few strands to make it fit the 100 A
breaker at EACH end.

later... Jim VE7RF

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 19, 2006, at 7:32 AM, pentalab wrote:

--- In ham_amplifiers@..., Tony King - W4ZT <w4zt-
060920@> wrote:

Which MOV's do you use and where do you get them?

### From Mouser... Digi key has em as well... aprx 2" tall x
1/2" thick x 2.75" wide base. Those are the 130 v units.
The closest ones for the 240 V service are 250 V rated. IMO..
250 V rated Mov's are cutting it too close.

RICH SEZ...Perhaps it might be a good idea to read the specs on

the 250v-rated MOV's, Jim.

### I did. And the 250 v rating is for a 250 V max rms CCS
condition. Depending on who makes a MOV.... clamp V is always
way higher than that.... which is why old books always said to use
twice the PIV needed for a FWB. These days it's triple the PIV
needed [at least for commercial recifier assys].

### MOV's are just a series of "grains" inside. The series
grains will start to short out with successive hits from
transients, spikes, surges, etc. The actual V rating of the MOV
will slowly start to go down. That's why 130V rated MOV's
are normally used. A 250 v rated Mov is cutting it too fine
for folks whose line V can reach 247-250 V. A few too many
hits on the MOV.. and it's continuous V rating will drop to the
point where it will conduct.... and short out. UNLESS it's
fused.... it's gonna burn up... or explode. Way too many house
fires caused by MOV's as is.

### Check out Joslyn's website in the USA. They are the number
one maker of commercial MOV assemblies for use in commercial /
industrial environments. You won't see any 250 v rated MOV's
used on any 240 V circuits. Their's come in several
configs.... like 130/135 v MOV's from each hot leg to neutral....
and or... 275 V rated Movs across the 240 V line.... or 225 V
rated Mov's from hot to neutral on a 208 3 phase setup.
Their's are all fused as well as alarmed. The latest versions
all have "event counter's" in em.. with time date stamps, etc.
Some of the ones we use at work are 4" square and 1"
thick...each... amd fused... and alarmed.

### Dahl sells MOV's. Why do you think his large bolt down
ones are ALL 275 v rated ....and not 250 V rated ???

### Rich... you just love to cut corner's and engineer stuff
right to the peg... with zero leeway. Rauch does the same. The
whole beauty of HB stuff is one can build it right the 1st
time.... with no corners cut... and loads of headroom.

Later.... Jim VE7RF

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

The boards are okay I guess but there is nothing special about the
current trips. All they do is sense a voltage drop across a resistor
with higher current and trigger an opto-couplers LED with it. This is
turn will open a circuit by a relay or transistor circuit.

Another thing I seen in one board is that they sample a little of the
screen or bias voltage and put that into a regulator to get the
control voltage for a relay, etc. That was done to keep from having
another coil on the transformer for low voltage. However, you need
one anyhow for the antenna relay, and others.

I design my own as to me any of the boards I've seen are a little
over-kill and over complicated for my taste. The more components
placed in any circuit raises the likelyhood of failure in the future
expotentially. I can make just as good of a regulator circuit with a
few transistors and zener diodes. This for either a series pass or
shunt regulator.

Best,

Will



--- In ham_amplifiers@..., "pentalab" <jim.thomson@...>
wrote:

--- In ham_amplifiers@..., Tony King - W4ZT <w4zt-
060920@> wrote:

Jim,

Don't you think that if a properly designed fault detection

circuit similar to the triode and tetrode boards available today
would have caused a primary circuit shut down saving the glitch
resistors from becoming a smoking pile?

### Partially agreed. Seems to me the 2 x triode boards
available, are based on using an external 24 vdc DPST RELAY...
whose contact's are in the 240 v primary. I don't see any

24

vdc RELAY's... with contacts rated for 100-400A. AC contactor's
on the other hand are all either DPST-DM or TPST-DM.... the

"DM"

means 'double make'.... IE: essentially each pole is two sets

of

contacts in series.... with an input lug... output lug... and a
huge bar on top that comes crashing down on the input/output.

### The DM arrangement is used [vs a dpst relay] simply cuz a
DM will break the arc into two arcs = essentially zero arc....
[when trying to break a full bore load from a xfmr/motor]

### I never see giant bolt down MOV's across the in/out poles
of any contactor's in commercial service.... but I always install
the big bolt down MOV's across all the poles of my own
contactor's in HV supplies anyway. The MOV's.. if used, should
be fused... in case they short out.... with a 120 v neon between
output side of fuse and neutral... to indicate a blown MOV fuse.

### I suppose one could modify the triode board output
easily.... and use the 24 vdc control circuitry, to
activate/deactivate the INPUT of a opto isolator..... the OUTPUT
side of the opto of course, could then be used to
activate/deactivate a..'normal' 120/240 vac solenoid coil of a
contactor. All that would be needed is an opto with a 24 vdc
input, that u sink or source... and a AC output... rated to

handle

the typ contactor solenoid coil. Most opto's have back emf
protection built into the output side.... still I'd use a mov
across the AC contactor's solenoid coil.

This isn't to minimize the value of a good fuse but to add that a
properly functioning circuit can fault the HV supply off so that

all you have to heat the glitch resistor is the stored energy in
the capacitor bank. This is precisely what G3/GM3SEK and WD7S do
with their boards. That way if you are testing and have one of
those "modified" fuses in the circuit, it will still not melt
anything down.

### agreed. Stored energy from the caps is pretty wicked with
100-300 uf and a 50 ohm glitch R.[and 7900 vdc no load].. IE:

3100-

9300 JOULES Everything else is just .."follow on energy".. from
the plate xfmr/FWB.

### I have seen pix of John Lyles stuff... where they used both
an electronic crowbar on the hv B+ to B- [used since pulse
rated service like YC-156's..rated for 67 A of plate current
means too much V drop across a typ glitch R... hence no glitch R
used in any pulse service amp].... and also electronic fault
detection circuits where by primary AC is removed. Also seen
pix of his HV diode boards.. used in 3 - phase HV pwr supplies...
which resemble charcoal.... when the crowbar failed.... and the
fault detection also failed... or was not fast enough.

### seems to me the 2 x triode boards wouldn't handle 3-4 A of
normal anode current... but might be modified ?

### I just wanted to keep it simple. Any electronic protection
would have to be in addition to properly sized HV fuses and
primary breakers.

### We use these electronic current sense devices at work
for huge HVAC motor loads,compressor's,chiller's, etc.[70 to 120+
kw normal operating load] It was explained to me, they are

used

since the start up current is wicked on this stuff... as in 3-7
x normal running current. So, instead of a breaker... it's a
current sense activated contactor. One of em crapped out
last spring.... causing a huge fire in our main 'motor control
center'... destroying a panel 8' wide x 7' tall. Incinerated
every wire in all 45 x conduits too.. a real mess. Turns out the
motor's were ancient. New motor's all have over temp shut
downs built into em. New [adjustable] current sensors have
redundant copies.. and fail safe modes.

### How do you know that every function on those triodes boards
is gonna function when you need it ? You need some kind of

"fail

safe" on em so if they lose pwr... everything shuts off.... or
perhaps two of em.... with say the outputs driving the
relay/conatctor... are in series... so if either one failed... it
would still shut off the AC primary, etc.

### A fast, CORRECTLY sized HV fuse will work every time.
Heck, you could even put 2 x identical HV fuses in series if
you wanted. As a side note, I have seen where fellow's are

using

2 x 5 kv [5 kv AC...7kv dc] rated Buss sand filled fuses in
series.... in lieu of a single 10 kv [10 kv AC...14 kv dc] 10"

long

HV fuse.... simply cuz they had a ton of 5 kv fuses... and had 10
kv dc HV supplies [for a 3 x 20]

### The 2 x triode boards are a good idea .. as long as any one
or more functions on em don't crap out. IF you had say a

GM3SEK

triode board installed on every amp you owned.... I'd have

one

extra spare board put away... for a 'fast' replacement..if
needed. Then fix the bad board at your leisure.

Later... Jim VE7RF

73, Tony W4ZT

pentalab wrote:

Gents

My buddy was recycling his old sand filled fuses... by

soldering

a single strand of 26 ga wire across the 5" long fuse.

Fine

so far.

Amp was running fine the other night... the next day... BOTH

HV

fuses were blown open..... and amp was off from the previous
night !

A real mystery. He then decided to solder TWO 26 ga wires
across each of the old HV fuses. Next step was adding a

small

resistor to one hot leg of 250 cfm fan.. to slow it down a

bit.

[cools the glitch..... which diss 450 w with a dead cxr...

100

w

on ssb]

At that point all hell breaks loose. The paralleled 100 ohm

225

watt wire wound glitch R's looked like u hit both of em with

a

propane torch for 30 mins each.... charcoal !! We know a

HV

to chassis fault occured... may have been a faulty RFC bypass

cap.

The point here is.... by oversizing the HV fuse.... the load

is

then transfered to the 100 A breaker in the 240 v main 200

A

panel.... which of course didn't blow open...... instead the
glitch R's fried themselves... !

You need well over 100 A to open a 100 A panel breaker.

Over sizing a HV fuse is bad enough.... and you guys want

to

operate with NO hv fuse at all ?? nuts.

BTW... that Dahl A-540 hypersil C core 253 lb plate xfmr I
have... has a .01 ohm primary.... and a 6.06 ohm sec [5200 v
tap] You got any idea how much current you can suck from

one of

these things ..... LOADS... as my buddy with the same 253 lb

xfmr

just found out. 253 lb xfmr with a core good for 20

KVA

CCS with a 100 A slo breaker... vs lowly glitch R [wound

with

nichrome wire no less] .... no contest.... glitch loses every
time........ unless a correct sized HV fuse is used !

later... Jim VE7RF





Yahoo! Groups Links

It sounds to me that Jennings wants things two different ways. First
they say don't momentarily test a vacuum cap with DC, but it's okay
to put one in service as a DC blocking cap, de-rated or not. From
everything I've ever read, the whisker problem is caused over time,
not in one minute of use. A DC blocker cap could be in an amp for a
lifetime. That's a good sales gimmick to sell hipots though. I've
never seen that warning either by Comet, or by any of the Russian
manufactured caps. If the cause is over the copper being too soft
used for the plate cups, it ought to be changed to a hard copper or
an alloy to stop it. I can see soft copper for the bellows, but not
the plate cups.

Thank God Rich and I didn't question the Jennings engineers on the
other list as we would have been sent another e-mail by the unknown
admin chastizing us for ever questioning these professionals with
published papers, etc....


Best,

Will



--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 19, 2006, at 2:59 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

...
RICH SEZ.... A 20kV rated C to block 7000V DC sounds like over-

engineering since the actual AC potential across the blocker is
minimal.

#### Rich... Jenning's engineers tell me when using either fixed
glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of the
FIXED vac cap has to be a MINIMUM of 3 X No load plate V......
other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

So why does the statement I quoted in the Jennings catalog on p.4
about DC operation state otherwise?

### Ur gonna get "whisker's" anyway in plate block service for
a fixed vac cap.... so the 20 kv cap... will actually be over
time... a lot lower than 20 kv. IF u Hi-pot test a fixed vac cap
that has been used for plate block service.... u will see it no
longer hi pot tests to 20+ kv any more.

### other than 11m ops... I never see fixed vac caps used as plate
blockers.

I do, Jim. Even 500pF is plenty for a DC blocker at 1.8MHz (XC =

190-

ohms) in typical amplifiers since RL is in the kilo-ohms range.

11m ops don't need much C for 11m... 100-250 pf max
is what they typ use. Their requirements are for a plate block cap
that handles LOTS of RF... esp for 4x20's, etc.

Tom Rauch apparently knows a Ham who mistakenly used a 100pF DC
blocker in a homebrew amplifier. The amplifier produced the

expected

output from 1.8 to 28 MHz. Sometime later, when a friend was

being

shown the amplifier, he noticed that there were only twp zeros

after

the 1 on the blocker cap. When a 1000pF cap was substituted for

the

100pF cap, the output did not increase although the tuning changed
slightly on the 1.8MHz band.
...
R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

pentalab wrote:

--- In ham_amplifiers@..., Tony King - W4ZT <w4zt- 060920@...> wrote:

Which MOV's do you use and where do you get them?

### From Mouser... Digi key has em as well... aprx 2" tall x 1/2" thick x 2.75" wide base. Those are the 130 v units. The closest
ones for the 240 V service are 250 V rated. IMO.. 250 V rated
Mov's are cutting it too close.. since my line V has been as high
as 247.2 V in summertime. Instead I use the 275 v rated Mov's
from Dahl.... made by "movistar".... almost same dimensions.

Thanks, wasn't sure which "big" ones you used.

### ACROSS poles of contactor's, you want 250-275 V rated Movs...
and not 130 v ones. IF you use fuses in each leg of the 240 v.... and just one opens... there is 240 v across the open fuse. Same deal with a contactor's poles.

Agreed.

## I install the 130 v rated Mov's between each hot leg and grnd.... right at the plate xfmr primary.... and 2 x 275 v rated mov's, in parallel, directly across the plate xfmr primary.
### You can get MOV's from mouser/digi key up to 1 kv. You can also series / parallel em too. Some will use 6 x series 1 kv mov's across the SEC of a 5200 v plate xfmr. Some commercial diode FWB's.. whether single/3 phase... will use a MOV across each diode..... and no cap/resistor. Most commercial bridges will use 3 x PIV for total number of diodes.

You do all you can and something can still fail but we've gone

from jumpering a fuse with copper wire to worrying about the protection circuit failing.
## yeah, I know. I'd trust a proper size fuse 1st... b4 any protection circuits. Both of em together is the real answer.

We are in agreement! I believe in the protection circuits too... there's
more to discuss about these things... see below.

### seems to me the 2 x triode boards wouldn't handle 3-4 A

of

normal anode current... but might be modified ?

Look at Paul's board... you can set it up with any external shunt

for

detecting a fault. Use the board to control any kind of contactor

you have.
#### I cringe when I see a full bore normal load being opened off
by a relay/contactor. Trying to open off an even bigger load during a fault condition is even more demanding.

True... but if the fuse doesn't open... or if it does, and the fault
doesn't clear, it's best to take the HV supply off line. The control of
the contactors will be slower than the fuse and should not see the huge
load as it opens... that may be a matter of timing.

### Watch the relay/contactor... when opening it off... while sucking 100+ A key down ! Imagine this again.... but with 2-4 x more current during a fault condition. Then toss in a high value C filter for fun. Peak current on the 240 V line every 8.3 msecs is 4-6 x normal operating current as is... never mind a fault condition.

yup... see above.

### I just wanted to keep it simple. Any electronic protection would have to be in addition to properly sized HV fuses and primary breakers.

And if your friend had used a correctly sized fuse, it wouldn't

have been an issue.

Simple is good (KISS) but not best when expensive tubes are at risk.

#### Correct. Which was the whole point of the title in the post. They also ran out of 750 Ma fast grid fuses one night.. and stuffed in some 3 A fuses ! If they had lost HV.... the grid current would peg when driven [normal]. The 750 ma grid fuse woulda blown asap... and input swr rises to infinity... and IPA/Xcvr shut down. With a 3 A grid fuse, they woulda damaged the grid.
### frying a pair of 225 w glitch R's is one thing... frying an expensive tube is another...esp when it's totally unwarranted.

And that is the point of using the triode control board. Note that it
will fault the amp off line, breaking the key line, if you exceed a
preset your grid cutoff current. There is lots to be said for not
transmitting into the amp with no HV on it.

Well, this thread started with your description of a failure caused
by your friend using copper wire instead of a real fuse. There is no device you can install that can second guess someone that is going to drop a copper bar in as a fuse. Everything we do is done with the expectation that the original circuitry will be used as
designed. Once part of it is defeated, then all bets are off! ;)

### agreed. I have no control over my buddy's amp. I can just make a suggestion...that's it. I think once they blow stuff up from oversizing.. that they probably won't do it again. A few spare correct size fuses is cheap insurance. If a fuse blows..... don't put in a bigger one... find the reason it blew !
Later... Jim VE7RF

So true... and even if the electronic protections are there, if one chooses to defeat them they will not help.

Thanks Jim, Tony W4ZT

On Nov 19, 2006, at 6:49 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Nov 19, 2006, at 2:59 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...>

wrote:

...
RICH SEZ.... A 20kV rated C to block 7000V DC sounds like over-

engineering since the actual AC potential across the blocker is
minimal.

#### Rich... Jenning's engineers tell me when using either fixed
glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of the
FIXED vac cap has to be a MINIMUM of 3 X No load plate V......
other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

RICH SEZ... So why does the statement I quoted in the Jennings

catalog on p.4 about DC operation state otherwise?

#### Dunno. Eimac sez the same thing, de -rate vac caps to
1/3 for plate block use !

I did not read this in any Eimac literature, and it does not make good sense since the prima facie consideration for a DC blocker is the current rating at 29MHz - since at 10m, the DC blocker typically carries c. 90% of the tank's RF circulating current.

The 11m ops also highly agree. The
11m ops tell me if they try and use a 16 kv test rated fixed vac
cap with 10.5 kv dc on it..... it will eventually arc.

Probably true since Jennings advises that 60% of the DC test V is the max WV when using DC + RF.

...

RICH SEZ... I do, Jim. Even 500pF is plenty for a DC blocker at

1.8MHz (XC = 190- ohms) in typical amplifiers since RL is in the
kilo-ohmS range.

#### No way. 500pf = 176 ohms of XC.

The rule of thumb is a 5 to one ratio for a coupling reactance. 176- ohms of XC and a RL of 176-ohms x 5 = 880-ohms or higher RL should be okay

IF the fixed VAC cap
can handle the RF current at 1.8 mhz.and plate load Z of tube is
HIGH.. and it doesn't screw up the tuning too much... it might
work. Big metal tube amps have plate load Z's of 900-1300 ohms.

At 7500v with 1500v on the screen, an 8171 has a RL of c. 1000-ohms.

...

RICH SEZ... Tom Rauch apparently knows a Ham who mistakenly used a

100pF DC blocker in a homebrew amplifier. The amplifier produced
the expected output from 1.8 to 28 MHz. Sometime later, when a
friend was being shown the amplifier, he noticed that there were
only twp zeros after the 1 on the blocker cap. When a 1000pF cap
was substituted for the 100pF cap, the output did not increase
although the tuning changed slightly on the 1.8MHz band.

#### yeah, I heard the same story.. plus another one...except it
was 150 pf.....and in both stories,it was a ceramic doorknob
cap... NOT a fixed vac cap. I wonder if anyone ACTUALLY measured
it with a LCR meter ?? I have measured doorknob caps that had
measured values out by a factor of 10...compared to the stamped
rating on the cap. So unless Rauch's buddy actually measured
it, we don't know what it was !

Smells kinda like bacon.

#### 100 pf = 884 ohms XC [1.8 mhz] gimme a break !

With a pair of 3-500Zs, RL is c. 2k, so 884-ohms would probably work okay if the Tune-C could tune it out.

### Stick a single 100 pf HT-50/58 cap in any 1500W amp....
run it at 1500 W RTTY/FM on 1.8 mhz for say 20 mins.... and
let us know what happens.

no

### A 3x6 has a 1100 ohm plate load Z.. when run full bore.
You don't wanna use a 100 pf cap.... including a vac cap.

### The plate block cap has to be able to handle the RF current..
without cooking.. so u gotta look at it's CCS rating... vs freq.
Ceramic caps don't handle much RF at 1.8 mhz... then again.. they
don't have that much RF through em on 160m. On 10m, the RF
through em is wicked...

Amen, Jim

esp with metal tubes.. with lotsa stray
anode to chassis C..... or even worse in schemes that use NO C1
cap.. and rely on tube C.

### with big metal tubes... plate load Z is always LOW. You
need plenty of plate block C... simply so u don't screw up the
tuning on 160m..... and also so you have a high enough current
rating on 10m.

### a 100 pf doorknob cap wouldn't last 30 seconds in a 3x3

Why would the capacitor dissipate heat?
...
R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

On Nov 19, 2006, at 7:32 AM, pentalab wrote:

--- In ham_amplifiers@..., Tony King - W4ZT <w4zt-
060920@...> wrote:

Which MOV's do you use and where do you get them?

### From Mouser... Digi key has em as well... aprx 2" tall x
1/2" thick x 2.75" wide base. Those are the 130 v units.
The closest ones for the 240 V service are 250 V rated. IMO..
250 V rated Mov's are cutting it too close.

Perhaps it might be a good idea to read the specs on the 250v-rated MOV's, Jim.

R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org