--- In ham_amplifiers@..., "Peter Voelpel" <df3kv@...>
wrote:

What is your reason for that large capacitor?
Are you using single phase at that power level?
I only use 2?F maximum or NONE in my large power supplies, so my

glitch resistors and magnetic breakers in the primaries of the
transformers is all I need

73
Peter, DF3KV

### You gotta be kidding us right ?? 2 uf or NONE !!

### here in NA... although 3 phase power [typ 12.5 kv /14.4 kv
and now 25 kv] is distributed all over town..... only one
leg /phase of that appears in residential area's.... where it's
dropped down to 240 /120 v [ they all use a grnded CT on the
sec]

### Typ pole pig xfmrs are 25/50 kva for multiple homes.. and
smaller for a single home in the countryside. How 16 homes
can all share the same 50 KVA xfmr [and all have "200 A"
service] is beyond me !

### 3 phase 208v/120v is used for business's.... and
condominium's, apartment flats etc. Even there.... each floor will
only get 208/120 single phase power... per suite. They make
special 208 v electric base board heater's. Stuff like 240 v
electric stoves.. and 240V electric hot water tanks/ 240 v
electric clothes dryer's.. are used on 208 v.... and just take a
little longer to heat up.

### For a single phase RF deck that needs say 6900V @ 3A... a
bare minimum of 34 uf will provide barely 3% ripple.
A 100 uf filter will provide 1% ripple... and far better
DYNAMIC Regulation.

## with a resonant choke set up..[single phase].. you could
easily get away with far less uf [for a given amount of ripple].

### with a 3 phase HV supply... BEFORE any filtering at all....
ripple is just 5%. [50% with a single phase supply]

### ripple freq on single phase is 2F [120 hz] It's 6F [360
hz] with 3 phase......... so if u have 3 phase... you are
laughing..and at a huge advantage over us.

### These modern lytics I have been talking about will also have
a 360 hz ripple current rating [always lower than the 120 hz
rating]

## Dahl plate xfmr's are very low ESR [typ just 8 ohms of DC
resistance on the sec]... are of low reactance type... and
will easily handle 150-400 uf of filtering [that's right from
Dahl himself].... they do.

### IMO 20-24 x 450 V rated lytics [esp the 2" x 4" types]
weigh zip ..compared to any choke... and are a dime a doz on the
surplus market....new.. in the unopened box.

### for ESSB purposes... 1.5 % ripple is about the max you want.
My buddy doubled the uf in his AL-1500... we could all HEAR the
difference right away. His HV dynamic regulation improved a
whole bunch. His entire amp plays a lot better now.

later... Jim VE7RF

--- In ham_amplifiers@..., "ad4hk2004" <ad4hk2004@...>
wrote:

- busily changing out 20K ohm, 100 watt, resistors in a Henry 3K
Ultra PS.... Man a bad PS load resistor can sure contaminate
everything when it decides to go open winding and arcs, sputtering
crap onto other components...
It took a bit of sleuthing to find the correct resistors for
replacing... Turns out Newark has em in Ohmite brand...

### I looked at the 8k/3 k ultra manual I have [same manual does
both amps]. On the 8k they use 5 x 20k-100w resistors. Diss is
a whopping 300 W CCS..... presumably so the resonant choke filter
will work. On the 8 k.. they used a 6000 V xfmr. .9 x 6000 =
5400 vdc no load.

### here's the kicker. IF just one bleeder opens up... the OCV
plate V shoots UP to a whopping 6000 x 1.414 = 8484 V !!!
Now the poor 3CX-3000A7 [rated for 5 kv] won't like it.... nor
anything else in the amp. You are lucking you didn't blow up ur
3k ultra.

### I gave up on choke input HV supplies yrs ago. The
resonant choke idea although a good one... is not so simple to
implement.

## My feeling is one is better off to use a C input filter. The
8 k ultra's plate xfmr is flaky at best. They could have used just a
3800 vac xfmr..... which would require LESS turns on the sec
winding.... which in turn would mean the xfmr coulda used bigger
ga wire in the 1st place.

### Dahl does a roaring business selling a 127 lb 10 kva
replacement xfmr + mating choke for the 8 k ultra. Stock, the
8k is only good for 2 kw out CCS rtty/ 3.5 kw pep cw/ssb....
then in real fine print on the schematic it sez..."200 w in... 5kw+
out".

### IMO... why put a ton of weight.. in the form of a choke in a
HV .... better to put the added weight into the plate xfmr in the
1st place... but that's just my opinion.

### I had some 3 k owners e-mail me a while back.... they were in
the 10m contest [where both cw/ssb modes are used the entire
weekend]. The poor fellow had forgotten to change the plate V
from High... to low... when switching from ssb... to cw. The
HV supply bit the dust shortly afterwards. [smoked plate xfmr]

## Henry has gone through so many plate xfmr manufacturer's, I have
lost count. The last supplier for the 3k/8k was ECA. And just
b4 Henry went "outa business"... they dumped ECA as a plate
xfmr supplier !

## I know several fellows who bought the Henry 16 uf - 7.5 kv
rated oil caps.... used em in 4-1000 amps.... and blew up the caps !

With the proliferation of the newer low esr lytics out there
[loads of em on the surplus market].. for a new hb project, they
can't be beat. The latest bunch I got are 50 miliohm and 10 A
CCS ripple current rating.... small things too.... 2500 uf @ 450
vdc... and just 2" diam x 4" long.

## It just seems nuts to me to suck 300 W ccs of bleeder...
then another 150 ma @ 5200 Vdc on idle [8k] on top of that.

### The 8k drops from 5400 vdc to 4700 vdc with a typ load. It
weighs a whopping 350 lbs too ! Since the alpha 87-A will
do 1.5 kw CCS... and the 8k will do just 2 kw CCS... I'd say
Henry just lost it... in the weight dept.

### BTW... a Dahl 10 KVA CCS xfmr weighs.. "just 127 lbs"

Later......Jim VE7RF

denny / k8do

Copper tubing is quite expensive overhere now.
10mm diameter is 3,60 Euro/m, 18mm is 6,40 Euro/m.
Prices are for small quantities of course.


73
Peter



________________________________

From: ham_amplifiers@... [mailto:ham_amplifiers@...]
On Behalf Of pentalab

and it's all dirt cheap....just like copper tubing.

On Oct 2, 2006, at 1:15 PM, ad4hk2004 wrote:

I check in here every few days to count on my mental fingers how many
times Rich rants on about Tom...
Then I go to the other shrine and count how many times Tom mentions
Rich...
It's umpteen to zero at this point...
One of em needs to give it a rest!

Zzzz

- busily changing out 20K ohm, 100 watt, resistors in a Henry 3K
Ultra PS.... Man a bad PS load resistor can sure contaminate
everything when it decides to go open winding and arcs, sputtering
crap onto other components...
It took a bit of sleuthing to find the correct resistors for
replacing... Turns out Newark has em in Ohmite brand...

Denny == Have you checked the max V rating of Ohmite's 100W resistors?

denny / k8do






Yahoo! Groups Links

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

On Oct 2, 2006, at 12:41 PM, pentalab wrote:

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

On Oct 2, 2006, at 12:15 AM, pentalab wrote:

### partially agreed. IF u have a HV fuse... and it opens...

the grid current will skyrocket..... hence another reason for a
fast grid fuse.

#### STEVEN SEZ... * OK, question - will the fuse blow if the
tube becomes unstable

(parasitic oscillation)

#### Been a long time since I have experienced parasites....

seems to me, both the plate current and grid current went
beserko.

RICH SEZ indeed

#### IF the HV fuse opened off... the grid fuse would blow

instantly...

RICH SEZ ..quite soon is more like it

### No, not quite soon,,, grid fuse blows asap ! instantly !

Instantly is pretty soon.

You remove the HV on any GG amp... AND drive it, with just a
little bit of power.. you will send the grid current through the
roof ! You drive it with full power.... and then lose the HV...
the grid current will wrap around the peg 4 x over..... and
blow the fast grid fuse.

### Fast fuses are called ..."rectifier fuses". The even
faster ones of the bunch are called .."semi conductor fuses".
You can even get fast .. "semi conductor fuses" up to 300 A

## You can get super fast fuses in 3agc.. anywhere.. like
Mouser/digi key/newark, etc.

### Never had a problem with parasitics destroying a tube.. as
long as glitch R installed... grid and cathode fuses... and a
HV fuse.

RICH SEZ... As I see it, a HV fuse is OBVIATED if the HV xfmr
primary is fused.



### DREAM ON RICH Rich ! You gotta be nuts to leave out the
HV fuse.... and soley rely on a typ slow breaker in the 240 V
primary !!! The fastest breakers known.. are
called "controlled Hydraulic magnetic breakers".... and the
fastest of them .... still isn't fast enough.

HV fuses are not fast enough to prevent gold sputtering from the grid of an 8877, 3cx800A7, et cetera.

## Here's why. The last HV supply I designed used 30 x
lytics... EACH is 3700 uf @ 350 V. We ran outa 3700 uf
units for the last 5 caps.. so we used 5200 Uf units @ 350 V.

### The entire mess > 135 uf !! Since joules [watt seconds]
goes to the SQUARE of the voltage..... u can easily see that the
total joules is sky high..... has to be. You want to run 10 x
the dc input as b4.... u require 10 x the energy in joules.

### Even on a SB-220, L4B, AL-1500, etc.... the stored energy
in the bank of lytics is just unreal.

The SB-220's 120J seems pretty real to me.

A Buss HVU series, sand
filled fuse [sized right for the job] OR a HB hv fuse [ one fine
strand between 2 x insulator's] will blow EXTREMELY
FAST......<2- msecs.

Peak current can go through the roof in under 1mSec.

### The ONLY way to speed up the primary 240 V fusing.. is to
supplement the typ "controlled magnetic hydraulic breakers"...
with super fast "semiconductor fuses" ....... or do like you
do.... and use a 40 A breaker..... which BARELY handles the
average load on unprocessed SSB. Of course, with a grossly
undersized breaker.... you only have two options..... pulse
tuning... and then straight to unprocessed SSB. Run a dead
cxr... even for 2 seconds, just to take some steady state
grid/plate/fil V readings.... and ur 40 A breaker will blow
open !! To do 14kw out.... you need a 100 A breaker !!

Been there. The original Plywood Box did 14-out PEP on SSB, it used a double 40A breaker and #4 Cu wire. I tuned it up with a 30pps, 30% duty-cycle tuning pulser, and it never tripped the breaker

### It's actually 106 A [and that's with 67% tank eff]

### Ur 100' of 4 ga wire has way too much loop resistance for
the peak currents on the 240 v line.

The HV dropped to c. 7800v on an ahhhhhh. What's wrong with that?

A bare minimum for just
a 30' run is 2 ga. It should be 3 x 000 CU.... regardless
of lenght.

### leaving out the simple HV fuse.. and relying on primary
breakers is a 100% sure fire way to destroy stuff.. including
tubes.

Perhaps an indirectly cathode could be damaged by over-current, but directly-heated cathodes are naturally current limiting. The 8170 in the Plywood Box amp was not damaged during a number of big-bang parasitic oscillations, but I disintegrated a few glitch resistors before I figured out that a glitch-R is Not supposed to be a fuse. .

...

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

What is your reason for that large capacitor?
Are you using single phase at that power level?
I only use 2?F maximum or none in my large power supplies, so my glitch
resistors and magnetic breakers in the primaries of the transformers is all
I need

73
Peter, DF3KV

________________________________

From: ham_amplifiers@... [mailto:ham_amplifiers@...]
On Behalf Of pentalab

## Here's why. The last HV supply I designed used 30 x
lytics... EACH is 3700 uf @ 350 V. We ran outa 3700 uf
units for the last 5 caps.. so we used 5200 Uf units @ 350 V.

### The entire mess > 135 uf !! Since joules [watt seconds]
goes to the SQUARE of the voltage..... u can easily see that the
total joules is sky high..... has to be. You want to run 10 x
the dc input as b4.... u require 10 x the energy in joules.

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

RICH SEZ...Correct. Jim. My thinking on NOT using a fuse holder is
that if the fusing element blows, the reason is not a defective
fuse, it has to be the whatever that caused the fuse to blow, so a
new fuse is not the total repair. Thus, when the fusing element
blows, the amplifier has to be disassembled anyway to find the
real problem, so a fuse holder would be of no advantage.

### Gimme a break ! The grid fuse could blow for several
reasons.... like SKY high swr... accidental overdrive....
underloading, both..... OR if the HV fuse blew open [and with amp
being driven, the grid current will wrap around the peg].

## once the reason for the grid fuse blowing is known.... it can
be quickly replaced... in mere seconds flat. Ditto with a
cathode fuse. A little longer to replace either of the HV fuses.

### I can stuff a screwdriver into the HV compartment, grnd
anything you want, short out caps, short the grid to the
cathode... run 15 kw into a dead short, wide open,,, drop a wrench
across the 240 v input, have the big Dayton blower crap out, lose
air to the tube , lose commerccial AC power from the street,
have transients, spikes , surges coming in off the street,
overdrive the amp, underload the amp, etc, etc... and you STILL
CAN'T blow anything up. I can even lay a dead short across the
diode FWB rectifier board.... and not take out any diodes.

### I can also short out the fil xfmr, or short out the + 120
vdc supply for the sped up vac relays, or short out the +12
vdc for the plate choke relay.

### My goal was to make it [RF deck + HV supply] 120% BULLET
PROOF!! Next step is to add the spark gap across the Vac load cap.
[heck a spark plug in open air.. set to arc at 1.7 kv will work]
We might add electronic grid + plate overcurrent protection
later on... + a HV sensor [which will inhibit TX... with low, or
NO hv present].

### The beauty of HB designs is.... you can easily add any or
all of this stuff in... at any time.... and it's all dirt cheap....
just like copper tubing.

Later... Jim VE7RF

I check in here every few days to count on my mental fingers how many
times Rich rants on about Tom...
Then I go to the other shrine and count how many times Tom mentions
Rich...
It's umpteen to zero at this point...
One of em needs to give it a rest!

- busily changing out 20K ohm, 100 watt, resistors in a Henry 3K
Ultra PS.... Man a bad PS load resistor can sure contaminate
everything when it decides to go open winding and arcs, sputtering
crap onto other components...
It took a bit of sleuthing to find the correct resistors for
replacing... Turns out Newark has em in Ohmite brand...


denny / k8do

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

On Oct 2, 2006, at 12:15 AM, pentalab wrote:

### partially agreed. IF u have a HV fuse... and it opens...

the grid current will skyrocket..... hence another reason for a
fast grid fuse.

#### STEVEN SEZ... * OK, question - will the fuse blow if the
tube becomes unstable

(parasitic oscillation)

#### Been a long time since I have experienced parasites....

seems to me, both the plate current and grid current went
beserko.

RICH SEZ indeed

#### IF the HV fuse opened off... the grid fuse would blow

instantly...

RICH SEZ ..quite soon is more like it

### No, not quite soon,,, grid fuse blows asap ! instantly !
You remove the HV on any GG amp... AND drive it, with just a
little bit of power.. you will send the grid current through the
roof ! You drive it with full power.... and then lose the HV...
the grid current will wrap around the peg 4 x over..... and
blow the fast grid fuse.

### Fast fuses are called ..."rectifier fuses". The even
faster ones of the bunch are called .."semi conductor fuses".
You can even get fast .. "semi conductor fuses" up to 300 A

## You can get super fast fuses in 3agc.. anywhere.. like
Mouser/digi key/newark, etc.




### Never had a problem with parasitics destroying a tube.. as
long as glitch R installed... grid and cathode fuses... and a
HV fuse.


RICH SEZ... As I see it, a HV fuse is OBVIATED if the HV xfmr
primary is fused.



### DREAM ON RICH Rich ! You gotta be nuts to leave out the
HV fuse.... and soley rely on a typ slow breaker in the 240 V
primary !!! The fastest breakers known.. are
called "controlled Hydraulic magnetic breakers".... and the
fastest of them .... still isn't fast enough.

## Here's why. The last HV supply I designed used 30 x
lytics... EACH is 3700 uf @ 350 V. We ran outa 3700 uf
units for the last 5 caps.. so we used 5200 Uf units @ 350 V.

### The entire mess > 135 uf !! Since joules [watt seconds]
goes to the SQUARE of the voltage..... u can easily see that the
total joules is sky high..... has to be. You want to run 10 x
the dc input as b4.... u require 10 x the energy in joules.

### Even on a SB-220, L4B, AL-1500, etc.... the stored energy
in the bank of lytics is just unreal. A Buss HVU series, sand
filled fuse [sized right for the job] OR a HB hv fuse [ one fine
strand between 2 x insulator's] will blow EXTREMELY
FAST......<2- msecs.

### The ONLY way to speed up the primary 240 V fusing.. is to
supplement the typ "controlled magnetic hydraulic breakers"...
with super fast "semiconductor fuses" ....... or do like you
do.... and use a 40 A breaker..... which BARELY handles the
average load on unprocessed SSB. Of course, with a grossly
undersized breaker.... you only have two options..... pulse
tuning... and then straight to unprocessed SSB. Run a dead
cxr... even for 2 seconds, just to take some steady state
grid/plate/fil V readings.... and ur 40 A breaker will blow
open !! To do 14kw out.... you need a 100 A breaker !!

### It's actually 106 A [and that's with 67% tank eff]

### Ur 100' of 4 ga wire has way too much loop resistance for
the peak currents on the 240 v line. A bare minimum for just
a 30' run is 2 ga. It should be 3 x 000 CU.... regardless
of lenght.

### leaving out the simple HV fuse.. and relying on primary
breakers is a 100% sure fire way to destroy stuff.. including
tubes.

RICH SEZ Also, a fuse is not as good as of a peak-current limiter
as a glitch R.

### A fuse is NOT a peak limiter at all... never was ! A fuse's
job is to INTERUPT CURRENT FLOW... that's it. The job of the
glitch R is to LIMIT CURRENT. You need BOTH... and the
glitch R should be 50 ohms.... even in a small amp.

### To really do it right... I install a 2nd HV fuse.... located
between ONE leg of the plate xfmr sec... and the diode board...
with this arrangement... there is NO way you can ever take out
the diodes.

### also install one reverse connected 6 A diode ACROSS EACH
lytic.

### In a small amp, use a 50 ohm 50 watt wirewound... OR 2 x 25
ohm-25 Watt units in series....[the 2 resistors can be several
inches apart.. easier to mount in some apllications.]

Later... Jim VE7RF

On Oct 2, 2006, at 12:15 AM, pentalab wrote:

--- In ham_amplifiers@..., Steven Grant <w4iiv@...>
wrote:

STEVEN SEZ... * In normal amateur service, i dont see how i could

ever drive the amp hard enough to roast the grid

even if mistuned (2 3-500Zs)
I dont tune with full power till im close to resonance btw
(maybe a 3CX800)

### partially agreed. IF u have a HV fuse... and it opens... the
grid current will skyrocket..... hence another reason for a fast
grid fuse.

#### STEVEN SEZ... * OK, question - will the fuse blow if the
tube becomes unstable

(parasitic oscillation)

#### Been a long time since I have experienced parasites.... seems
to me, both the plate current and grid current went beserko.

indeed

IF
the HV fuse opened off... the grid fuse would blow instantly...

quite soon is more like it

### Never had a problem with parasitics destroying a tube.. as
long as glitch R installed... grid and cathode fuses... and a HV
fuse.

As I see it, a HV fuse is obviated if the HV xfmr primary is fused. Also, a fuse is not as good as of a peak-current limiter as a glitch R.

later... Jim VE7RF








Yahoo! Groups Links

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

On Oct 1, 2006, at 4:05 PM, Bob Green wrote:

Hi all –

I have what used to be a working SB-200 amp. It is not working well
at all now. I really want to get it on the air for the CA QSO Party
next weekend. I come to you as a last resort.

I used to be able to get about 700 watts out on 20M. Now I’m lucky
if I can get 50-80 out, with 40-70 IN. The 572 plates get bright
red-orange, but no (or nearly no) power out. Someone on the OTHER
reflector suggested the 33 ohm grid resistors were open. They are
not. One was about 33.9 ohms and the other was about 45 ohms, but
definitely NOT open.

45 ohms is 36% high. If the outside of the resistor is not burned,
the resistor may have been damaged by an intermittent condition,

In looking at AG6K’s website, it shows the 33 ohm resistors in
parallel with approx 900 pf directly to ground, not through the
Heath bias circuitry. I have no problem connecting the amp like
this, but will it really help?

It does not help stabilize the amp, it's a mod that obviates the
cockamamie Heath T/R biasing scheme and allows one to do the needed
high-speed switching mod.

And how do you read grid current, since none would be flowing
through the meter?

Grid current flows from the grid through the 33Ω resistor to gnd,
from gnd through the grid current meter shunt, to the negative HV,
the same way the SB-220 meters grid current. .
... ...
cheers, Bob

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

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

On Oct 1, 2006, at 4:43 AM, pentalab wrote:

RICH SEZ...... especially if you just love to repair

amplifiers.

### Build a 3000A7 linear.. and try it yourself. The one turn
chrome suppressor from the 8-K is essentially doing...nothing.

RICH SEZ...Agreed. Henry parasitic suppressors typically have a

Q of >5 at > 100MHz. IMO, it's better to keep suppressor Q under 2.

### The 8 k is rock stable... with a 1 turn strap of 1" wide
chrome plated material... which is doing nothing..... toss it... and
it's still rock stable.

RICH SEZ... How long is the 1" strap used to ground 3=500Z socket
pins?

### about 1.5".... which measures ZERO inductance on my B+K 875B
LCR meter. ... which only reads down to .1 uh. Heck.. a 3' long
piece of 3/4" wide CU strap still reads 0.0 uh.


### All I know is that when you directly strap all

6 x grid pins, with wide strap, to the chassis, the SB-220, SB-
221, TL-922 become rock stable...

RICH SEZ... Not in my experiences. Increasing the grid's resonant

frequency should theoretically allow the grid to better shield the
output from the input at higher frequencies -- thereby increasing
VHF stability.

### DEEP SIX the "theoretically part". When doz's of
fellows tell me that after grnding the grids to chassis with
strap on the TL-922 and SB-220/221's makes em rock stable,
believe it. And they also re-installed the STOCK OEM
suppressor's to boot.



###... as to why it works is perhaps the grids are now really
grounded...

RICH SEZ Up to what frequency?

### Dunno... probaly good to 6m... since 3-500Z's seem to
work just fine on 6m... in GG... with the grids dirctly grnded.

### Now the AL-80BX and Ameritron with the 2 x 3-500Z's do

have the grids directly grnded.... and STILL spit, arc, etc.

Perhaps it involves something other than the grids -- such as the

Q

of the R/L VHF suppressor @ 100MHz? Please describe the VHF
suppressors.

### TYP Ameritron junk.

L4Bs are inherently more stable than most other 3-500Z amps

because they use less HV to supply the anodes -- and that
decreases gain.

### agreed. They also use real suppressor's.

### I once built asingle 3-400Z in 1974... had 5000 vdc no
load on it. Rock stable.... with grids directly grnded... and a
suppressor made with 12 ga wire and a globar.

### Lemme ask u this. IF u were gonna design and build a 2 x 3-
500Z 80-10m amp from scratch.... would directly grnd the grids
with strap..... OR install 6 x 200 pf caps + 2 x RF
chokes ??????


RICH SEZ... a glitch resistor is needed to physically limit peak
filter-cap current to under 200A during a glitch . Neither a HV
fuse nor a typical over-current trip circuit is fast enough or
rugged enough to do this job.

### a HV fuse does NOT limit current. It INTERUPTS it.

### a FAST HV fuse..a cathode fuse....

RICH SEZ.......250 V rated ?

### 250 V rated cathode 3agc fuse work just fine. As
explained b4... they will NEVER see 3000 vdc in a million yrs.....
not with reverse connected diodes between chassis and B- ...
and more reverse connected diodes across both grid + plate
meter's.


### and a real 50 ohm, 50-100 w glitch resistor.

RICH SEZ... Agreed, but limiting peak current that severely with a
3kV PS may not be needed.

### Do u want to limit the current or not ?? A 50 ohm 50 W wire
wound is good up to 1 A of plate current in normal operation...
limits current to 60 A...... then the HV fuse blows instantly...
followed by the grid fuse. [since grid I will skyrocket, with
drive applied, and NO HV]



### Use of a digital delay for cw + ssb will help
immensely.....

RICH SEZ no delay is needed if the relays are faster than the
transceiver.

### I'm using fast RJ1-A's on the input [+120 vdc speed up]
and slower paralled sped up vac relay's on the output [8 msec]. I
don't want the drive being applied... and still no ant
connected... yet.

### these modern xcvr's crank out globs of RF instantly...

RICH SEZ 5mS is typical

### measure it on SSB. Moot point. The MK-V's have an
adjustable 0-30 msec digital delay on cw [no truncated
anything]. On ssb we use the 10 msec delay scheme.. and play
it safe.

RICH SEZ An RJ-1 or HC-1 makes in c. 1.8mSec with the circuit at:

However such speed requires 100 to 150 volts at the other end

of the current limiting R.

### Even paralled RJ-1A's are flaky on the output of a big amp.
I used a paralled pair of Jenning/Kilovac/ Gigavac next size up
units... rated at 10 A @ 32 mhz.... and tons of voltage. Handles
an easy 20 kw dead cxr on 10m.... and more on the lower bands.

## They are not fast though. Stock, they are 18 msec operate..
and 9 msec release. I speed em up with +120 vdc... chops the op
time way down.... to 6-7 msecs. No qsk.. fast vox cw/ssb.

### Also, xcvr's like the ICOM's.. will have peak overshoots.
That's easy to fix...... just use fixed dc voltage.. fed to the
ALC jack at all times !

RICH SEZ Turning the mic. gain down to barely any ALC greatly
reduces overshoot and usually slightly increases PEP. .

### Waste of time. I use loads of external audio rack gear. My
Aphex 320A levelor /compressor/limiter feeds a constant level of
audio into my Aphex 720A "Dominator" [split band
limiter/distortion cancelled clipper]. I can get an easy 200 w
pep.. or any pwr level I want... and not have the ALC meter even
budge.. scream all I want.


#### Whoa nellie ! Believe me... plan A was to use 1" wide

strap.... which would mean using a 6" long - 150 w CCS globar...
which I didn't have on hand. At 15 kw... on the high bands, the
RF current is just unreal through that suppressor strap !!!

RICH SEZ Agreed. For an 8171 on 10m, expect 25A-rms.

## It's a helluva lot more than that.


### Here's my problem with Nichrome. It GLOWS ORANGE on the

higher bands.

RICH SEZ Use a width that will carry the current. I use 4-mil
stainless-steel shimstock, cut to the width I need for big ones.

### Why not just use the correct component in the 1st place ??
A 90 w globar 3/4" diam x 5" long....... bullet proof... and
nothing gets hot.... rock stable.



RICH SEZ But you would achieve a lower VHF Q if you used stainless-
steel shimstock or Ni-Cr ribbon.


### agreed, but the above globar + a few turns of WIDE Silver
plated strap do the job. Just increase the turns till parasites
go bye bye.

### U can do the exact same thing on a SB-220 if u want. Just
increase the turns in the suppressor till parasites gone.
Resistor getting hot on 10m/burning up ?? Gee... replace with
the correct component... a small 10-25 w globar.

#### IMO use what ever works. I had a ton of globars on hand...
and loads of strap. They carry 3' x 7' sheets of CU... in any
thickness... and I just get em to chop it in 3' lengths... usually
in 3/4" widths.. and also 1" widths. The globar method
involves soldering..nothing.

## all connections to tank coils and bandswitch contacts use
machine screws.

### BTW, the new Gigavac heavy duty relays all have machined
and tapped threads on the connections... for a 6-32 screw....
so takes strap easily. On the jenning's and kilovac units...
they stuff 8 ga wire inside the same tubes.. and solder em.

Later... Jim VE7RF

--- In ham_amplifiers@..., Steven Grant <w4iiv@...>
wrote:

STEVEN SEZ... * In normal amateur service, i dont see how i could

ever drive the amp hard enough to roast the grid

even if mistuned (2 3-500Zs)
I dont tune with full power till im close to resonance btw
(maybe a 3CX800)

### partially agreed. IF u have a HV fuse... and it opens... the
grid current will skyrocket..... hence another reason for a fast
grid fuse.

#### STEVEN SEZ... * OK, question - will the fuse blow if the
tube becomes unstable

(parasitic oscillation)

#### Been a long time since I have experienced parasites.... seems
to me, both the plate current and grid current went beserko. IF
the HV fuse opened off... the grid fuse would blow instantly...

### Never had a problem with parasitics destroying a tube.. as
long as glitch R installed... grid and cathode fuses... and a HV
fuse.

later... Jim VE7RF

--- In ham_amplifiers@..., Steven Grant <w4iiv@...> wrote:

What we are not seeing is when this fuse goes, the tube is already

bad!

What the grid fuse does is protect the filament transformer IMO

Steven W4IIV

### IF the tube fil shorted to the grid... u may well be
correct. The CT of the fil xfmr would be tied to the
chassis... via the neg terminal of the grid meter [through the grid
fuse... then to chassis] This would short out the CT to BOTH
halves of the fil xfmr sec... frying it........ unless either a grid
fuse installed... or a fuse installed in the pri of the fil xfmr.

later... Jim VE7RF

--- In ham_amplifiers@..., "Mike Sawyer" <w3slk@...>
wrote:

I see that there's one of these on that e-auction place for ~$57.

I
understand that this is a pretty good tube since it doesn't require
any special socket. If I didn't have so many irons in the fire, I'd
snag this. But hell, I don't use my amp enough as it is. So here it
is
with about 2hrs. to spare.

Tube_W0QQitemZ110037289265QQihZ001QQcategoryZ58174QQrdZ1QQcmdZViewIte
m

Mod-U-Lator,
Mike(y)
W3SLK

### The F1 version only has a MU = 5......... so it's useless
for GG !

### It looks IDENTICAL to the 3CX-3000F7 MU= 200 which can be
used in GG. Both versions have flex leads to both the fil
connections AND the grid..... which makes it a pain to mount.

### Here's what fellows do to mount a 3000F7. Disconnect the
flex lead for the grid... and toss it. Replace with a vac var
flange for the same od of the grid ring on the tube.

### Bolt the new vac variable flange to the chassis... so the
tube is pinched/compressed by the new vac var flange. Connect the
fil flex leads to the bifilar [shorten em up 1st]... done.

### some will make /machine a split block of aluminium... both
halves of this block are simply bolted to the chassis... and
transverse machine screws compress the two halves together....and
pinch/compress the grid ring on the tube......again, the original
flex lead to the grid is tossed 1st... and fil leads are
connected as above... done.

### This info is just in case somebody comes across a F7 version
[identical tube to a 3CX-3000A7].

Both the vac flange and machined block idea came from some 11 m
op.... who had 3 x F7's in parallel... mounted exactly as
described... and that was in a mobile !!

later...Jim VE7RF

This wouldnt be the core problem I guess but if a
33 ohm resistor has changed to 45 ohms it needs to
be replaced, I hope you have done it already.

To me it sounds like the problem is on the output
side, since you can drive "input power" , check
from DC blocking cap and all the way to antenna
connector. Dont forget the RFC and the power
meter pickup.

73 Jim SM2EKM
----------------

Bob Green wrote:

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Check your plate blocking cap and pi - network components. Also TR RELAY contacts. Sounds like you have plenty or drive but output circuit may beon th ewrong frequency. Plate and load settings changes would be a clue. You could be tuning up on 10 meters. Blocking cap open would not couple rf to the tank.?wa1gfz

Bob Green wrote:

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Hi all –

I have what used to be a working SB-200 amp. It is not working well at all now. I really want to get it on the air for the CA QSO Party next weekend. I come to you as a last resort.

I used to be able to get about 700 watts out on 20M. Now I’m lucky if I can get 50-80 out, with 40-70 IN. The 572 plates get bright red-orange, but no (or nearly no) power out. Someone on the OTHER reflector suggested the 33 ohm grid resistors were open. They are not. One was about 33.9 ohms and the other was about 45 ohms, but definitely NOT open.

In looking at AG6K’s website, it shows the 33 ohm resistors in parallel with approx 900 pf directly to ground, not through the Heath bias circuitry. I have no problem connecting the amp like this, but will it really help? And how do you read grid current, since none would be flowing through the meter?

I’m kind of new at this, so if someone would be willing to call me instead of just jotting down some thoughts, I’d really appreciate it. Like I said earlier, I want to get this beast ready for a contest next weekend. I have two new tubes, but would rather not use them unless it is really necessary.

Thanks in advance for your help!? My phone is 909-866-7742. If you would rather, send me your phone number, and I’ll pay for the call. I have unlimited long-distance service.

73,

Bob Green W6BBL

w6bbl@...

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