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On Oct 25, 2006, at 1:04 PM, craxd wrote:

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

On Oct 24, 2006, at 9:05 PM, craxd wrote:

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

...
Correct. He didn't like the fact that an oscilloscope indicated a
worst-case potential in a SB-220 that was only about 1/3 of what he
predicted it would be. This potential is on the verge of arcing the
Tune-C, so even if the voltage tried to rise much higher, the cap
would zap and limit the voltage like a zener diode. The reason he
wanted the potential to be higher was to explain away what I said was
parasitic arcing by the SB-220's occasional 110MHz oscillation.

The peak or peak to peak voltage one reads is exact,...

Porcine shampoo. I'm a guy who used to calibrate oscilloscopes.

Wouldn't you agree they're exact to within their tolerance?

No. Exact means without error -- within tolerance means within a specified error.

If the cal equipment used is correct, and the scope is ran
in a similar enviroment temperature wise, etc, it should show
close to the same as what it was calibrated to read.

Correct -- which is not without error.

That is
provided it's withing calibration and hasn't been tampered
with. I'm not saying it's exact with no deviation, but it's
one of the most exact ways we have reading an AC voltage. 3%
or less tolerance is pretty darn good. According to the
Tektronix manuals, they should be capable of better than 3%.

A calibrated oscilloscope is one way power meters can be

calibrated

and it's much faster than using a bomb-calorimeter. However, an
oscilloscope is as useless as tits on a boar hog for measuring
cleanliness of a SSB signal.

Well it's according to what you term clean. Harmonics no, unless

you

build or use a front end for this like the poor mans spectrum
analyzer, or one of the commercial add-on units. Over modulation,
hum, noise, regeneration, and parasitics can all be seen using a
standard scope.

But not SSB IMD.

...

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

Best,

Will





Yahoo! Groups Links

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

MFJ does sell a stand alone dip meter that's decent as I have
one of them. MFJ doesn't manufacture this meter either, they
have them branded by an asian manufacturer. It's the same dip
meter as the Leader solid state and a few others. I'd trust
it more than the analyzers that MFJ made by a long shot.

I compared the one they're selling to the Heathkit one I have,
and they work similar to the same.

Best,

Will


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

On Oct 24, 2006, at 2:49 PM, pentalab wrote:

--- In ham_amplifiers@..., Bill Turner <dezrat@>
wrote:

ORIGINAL MESSAGE:

On Mon, 23 Oct 2006 00:20:30 -0000, "craxd" <craxd1@>
wrote:

If a dip meter shows a
resonance, there is a resonance at its tuned frequency. Forget
reading the freq off the dial, simply couple it to a known

accurate

freq counter, it will show the truth if you want precision.

------------ REPLY FOLLOWS ------------

One needs to be careful with this. The typical single-tube or
single-transistor dip meter can be pulled considerably off the

true

resonant frequency if coupling is very tight to a high-Q circuit.

Just

physically move the dip meter away far enough so the dip is

barely

perceptible and the accuracy will improve greatly.

If you have used a dip meter much, you have no doubt had the
experience of tuning slowly across the dip, and as you continue

tuning

have the dip suddenly disappear as the pulling effect disappears.
Loose coupling will prevent this from happening.

### Highly agreed. Loose coupling is as good as it gets.... for
acuracy anyway. Mike Stahl, K6MYC warned me about this 25 yrs
ago.... he didn't trust em.. when tweaking yagi's.... I wouldn't
either.

According to a friend who loaned him a dipmeter, he did not

realize

that a plug-in coil had to be inserted to make it work.

### For a real laff.... I bought the "mating" grid dip osc
coils for my MFJ-259 analyzer. Two coils cover the entire
spectrum. I can't grid dip ANYTHING with em... even simple
stuff.. like a coil in parallel with a cap... on the test bench.
Then I find out nobody else can grid dip anything either! Then

Rauch

sez they don't really work. They still don't. It was
suggested not to buy the optional coil(s).

With MFJ, $elling is the object, working is not

...

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

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

On Oct 24, 2006, at 9:05 PM, craxd wrote:

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

On Oct 22, 2006, at 5:20 PM, craxd wrote:

Jim,

It's a wonder Tom didn't add a "by the way" saying, scopes and

dip

meters are very inaccurate and should never be used. : ) At

least

he

answered you by e-mail, he never would me.

He did not tell me this via e-mail. He said dipmeters were

worthless

during a discussion of various means of grounding grids after a
dipmeter measurement showed a result that contradicted his dicta
about grounding grids.

No, I meant I wouldn't doubt that he would have said
this to Jim.

If a scope is calibrated properly, or a dip meter the same, they
can't lie. They can only show you the truth.

That IS the problem here.

If a dip meter shows a
resonance, there is a resonance at its tuned frequency. Forget
reading the freq off the dial, simply couple it to a known

accurate

freq counter, it will show the truth if you want precision. A
calibrated scope can only show a waveform that it produces from

what

it sees at the input jack.

Correct. He didn't like the fact that an oscilloscope indicated

a

worst-case potential in a SB-220 that was only about 1/3 of what

he

predicted it would be. This potential is on the verge of arcing

the

Tune-C, so even if the voltage tried to rise much higher, the cap
would zap and limit the voltage like a zener diode. The reason he
wanted the potential to be higher was to explain away what I said

was

parasitic arcing by the SB-220's occasional 110MHz oscillation.

The peak or peak to peak voltage one reads is exact,...

Porcine shampoo. I'm a guy who used to calibrate oscilloscopes.

Wouldn't you agree they're exact to within their tolerance?
If the cal equipment used is correct, and the scope is ran
in a similar enviroment temperature wise, etc, it should show
close to the same as what it was calibrated to read. That is
provided it's withing calibration and hasn't been tampered
with. I'm not saying it's exact with no deviation, but it's
one of the most exact ways we have reading an AC voltage. 3%
or less tolerance is pretty darn good. According to the
Tektronix manuals, they should be capable of better than 3%.

A calibrated oscilloscope is one way power meters can be

calibrated

and it's much faster than using a bomb-calorimeter. However, an
oscilloscope is as useless as tits on a boar hog for measuring
cleanliness of a SSB signal.

Well it's according to what you term clean. Harmonics no, unless

you

build or use a front end for this like the poor mans spectrum
analyzer, or one of the commercial add-on units. Over modulation,
hum, noise, regeneration, and parasitics can all be seen using a
standard scope.

But not SSB IMD.

...

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

Best,

Will

Hsu,

In reality, you can't compute the power output the transformer
is capable of that way. Bill Orr done a carry over from the
ARRL Handbook, or it was vice versa. The central core area in
square centimeters or sq inches is what determines the power
handling ability of the core, and the wire size determines the
power handling ability of the wire. You could have enough iron
in the core, but the wire be undersized, or you could have
heavy wire and a small core where a transformer could be close
to saturation. I started writing a complete section on this in
wikipedia that shows all the formulas used to calculate a
transformer size. There, you'll find the formula for power
output. You need to know the current density of the wire (J)
they ran the transformer at, or in how many circular mils per
ampere. That is generally somewhere between 750 to 1500 cir
mils per ampere. The higher the number, the more power it will
handle without getting to hot. A brick on the key amp should be
above 1000 cir mils per ampere, up to say around 1200. 1500 is
for one in a hot enviroment. You also need to know what the
flux density is they run the core at. 12 kilogauss is a good
number to start with, but if Hipersil, it's around 15-16
kilogauss. You also need to know the line frequency (f), the
window area (W) in square centimeters or inches (height x width),
and the central core size (a) in square centimeters or inches
(width x depth). That gives the following formula;

P = 0.707 x J x f x W x a x B

This is the way the transformer designer does it correctly.
The weight can only give a rough guess, nowhere near exact.

See;



Best,

Will


--- In ham_amplifiers@..., "Hsu" <Jbenson@...> wrote:

Hi ,
Could someone can tell me how much output power of TL922's HV

transformer?

I have an Bill Orr's Radio handbook, there is some curves ,in a

chart, transformer weght in pound VS amplifier power capcity in vary
service,but I do not know how to calculate transformer's output
power by its weight.

73! Hsu

Hi ,
Could someone can tell me how much output power of TL922's HV transformer?
I have an Bill Orr's Radio handbook, there is some curves ,in a chart, transformer weght in pound VS amplifier power capcity in vary service,but I do not know how to calculate transformer's output power by its weight.
73! Hsu

### why doesn't somebody offer an amp in kit form these
days ??? That would be the ticket. The end user would have a
better idea how to repair it... since he built it in the 1st
place ???
**

Hmm, as someone who has lost his butt in every possible business known
to man except ham radio <smarter than that, stupid as I am> it took me
about 4 uS to see problems with his idea.. The price of metal
stampings and machined parts that have been drilled and tapped,
cleaned, powder coated and baked, then shipped to your plant, will
take your breath away...The cost of the components is 98% of the
finished amp.. So, you are going to offer a kit amplifier that is
within 2% of the price of an assembled one... Guess what your sales
will be? And the ones that do sell will, ala Heathkit, require that
you have a repair department to take in the crippled amps that the
buyer swears is defective design and components because he doesn't
make mistakes, and he did NOT run it key down, untuned for 4 hours...
Then your tech finds stripped threads, broken components, things
backwards, partially melted tubes, etc., and you have the joy of
calling the customer and explaining that HE broke it and now it is on
his nickel for repairs...
After he gets done cursing you out in 3 tongues and threatening your
unborn children, you realize that this business is, "just sooo much
fun."...

denny / k8do

On Oct 24, 2006, at 5:18 PM, pentalab wrote:

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

On Oct 24, 2006, at 1:35 AM, pentalab wrote:

### This sucks... and I don't like it one bit.

RICH SEZ... So use Matsushita/Panasonic MOFs instead of wire-wounds.

### Rich have u actually tried opening off one resistor [in a

one resistor per cap set up] and fired up the supply with a
small variac ??

RICH SEZ... Are you crazy? I was about 20-feet from where that

sucker exploded in the cal lab.

### Or should I not think about it... and hope my 24 x new

2500 > UF @ 450 V lytics don't got off like firecracker's
someday ??

RICH SEZ... To me, it sounded more like a jumbo cherry bomb.

Panasonic MOF resistors are pretty reliable.

### Flash ! with 4 x resistor's per cap... and one cut

loose. [assuming caps are no more than 75% of their v rating] The
one cap with the bad R will be almost maxed out.

RICH SEZ... That would work.

### 4 x resistor's in parallel = 25 K = lotsa heat per
cap. Probbaly 6-8 x resistor's.... each say 600-800K... all
in parallel... PER cap, would be the ultimate solution.....

then if anything opened up.... no chance of all ur caps blowing

up. The heat would be zip... per resistor.

ok problem solved.... now i can sleep

RICH SEZ.... But what if the sky falls?

later........ Jim VE7RF

########### Here's my problem Rich.... Those 2500 Uf @ 450 V CD
brand 10 A CCS ripple current rated caps I got NEW, by the case
load are listed at an unreal price tag.... like $100.00 EACH...
in single lot quantities. I have 72 of em... and will be using
em in groups of 24. I got em dirt cheap... they all tested
good, when checked on the bench. I would be just pissed if they
started exploding cuz of even the remotest chance of one resistor
lead opening.

So don't use WW resistors to equalize them.

### So... the real solution [aside from the usual 1 kv-6A safety
diode, rvs connected across eacg lytic] is to parallel 6 x 300 K
MOF resistors across EACH cap. [50 K for the paralled mess].

What is the V-rating and P rating of the 300k resistors?

If one ever opened... the voltage would only increase 20% on
that one cap. Total diss is 53 W. Each of the 144 resistor's
would only dissipate .37 w. Heck, with 6 x 150 K
resistors, Total diss rises to 106 W.... or a measely .74 watt
for each of the 144 resistor's.

### For a 8000 V [no load] supply... with 24 x caps..... normal V
per cap is 333 V [74% of the 450 V max rating]. With 6 x 300K /6
x 150 K resistor's across each cap.... and say one of the 6 opened
up.... V across that one cap will increase to 400 V.......well
within the 450 V rating of the cap....... end of problem.... end of
story.

### later...... Jim VE7RF






Yahoo! Groups Links

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

On Oct 24, 2006, at 2:49 PM, pentalab wrote:

--- In ham_amplifiers@..., Bill Turner <dezrat@...>
wrote:

ORIGINAL MESSAGE:

On Mon, 23 Oct 2006 00:20:30 -0000, "craxd" <craxd1@...>
wrote:

If a dip meter shows a
resonance, there is a resonance at its tuned frequency. Forget
reading the freq off the dial, simply couple it to a known

accurate

freq counter, it will show the truth if you want precision.

------------ REPLY FOLLOWS ------------

One needs to be careful with this. The typical single-tube or
single-transistor dip meter can be pulled considerably off the true
resonant frequency if coupling is very tight to a high-Q circuit.

Just

physically move the dip meter away far enough so the dip is barely
perceptible and the accuracy will improve greatly.

If you have used a dip meter much, you have no doubt had the
experience of tuning slowly across the dip, and as you continue

tuning

have the dip suddenly disappear as the pulling effect disappears.
Loose coupling will prevent this from happening.

### Highly agreed. Loose coupling is as good as it gets.... for
acuracy anyway. Mike Stahl, K6MYC warned me about this 25 yrs
ago.... he didn't trust em.. when tweaking yagi's.... I wouldn't
either.

According to a friend who loaned him a dipmeter, he did not realize that a plug-in coil had to be inserted to make it work.

### For a real laff.... I bought the "mating" grid dip osc
coils for my MFJ-259 analyzer. Two coils cover the entire
spectrum. I can't grid dip ANYTHING with em... even simple
stuff.. like a coil in parallel with a cap... on the test bench.
Then I find out nobody else can grid dip anything either! Then Rauch
sez they don't really work. They still don't. It was
suggested not to buy the optional coil(s).

With MFJ, $elling is the object, working is not

...

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

On Oct 24, 2006, at 9:05 PM, craxd wrote:

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

On Oct 22, 2006, at 5:20 PM, craxd wrote:

Jim,

It's a wonder Tom didn't add a "by the way" saying, scopes and dip
meters are very inaccurate and should never be used. : ) At least

he

answered you by e-mail, he never would me.

He did not tell me this via e-mail. He said dipmeters were

worthless

during a discussion of various means of grounding grids after a
dipmeter measurement showed a result that contradicted his dicta
about grounding grids.

No, I meant I wouldn't doubt that he would have said
this to Jim.

If a scope is calibrated properly, or a dip meter the same, they
can't lie. They can only show you the truth.

That IS the problem here.

If a dip meter shows a
resonance, there is a resonance at its tuned frequency. Forget
reading the freq off the dial, simply couple it to a known

accurate

freq counter, it will show the truth if you want precision. A
calibrated scope can only show a waveform that it produces from

what

it sees at the input jack.

Correct. He didn't like the fact that an oscilloscope indicated a
worst-case potential in a SB-220 that was only about 1/3 of what

he

predicted it would be. This potential is on the verge of arcing

the

Tune-C, so even if the voltage tried to rise much higher, the cap
would zap and limit the voltage like a zener diode. The reason he
wanted the potential to be higher was to explain away what I said

was

parasitic arcing by the SB-220's occasional 110MHz oscillation.

The peak or peak to peak voltage one reads is exact,...

Porcine shampoo. I'm a guy who used to calibrate oscilloscopes.

A calibrated oscilloscope is one way power meters can be calibrated
and it's much faster than using a bomb-calorimeter. However, an
oscilloscope is as useless as tits on a boar hog for measuring
cleanliness of a SSB signal.

Well it's according to what you term clean. Harmonics no, unless you
build or use a front end for this like the poor mans spectrum
analyzer, or one of the commercial add-on units. Over modulation,
hum, noise, regeneration, and parasitics can all be seen using a
standard scope.

But not SSB IMD.

...

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

Sorry,

They do say what the form was changed to, I didn't see it the first
read. It now is made with a glass-based phenolic tubular core. That
would be similar to acting like micarta I would think.

Best,

Will


--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:

All,

Below is the link to the Oren Elliott website and the page with the
roller inductors. It doesn't say what the form material is, just

that

it's "newly redesigned".





Best,

Will

All,

Below is the link to the Oren Elliott website and the page with the
roller inductors. It doesn't say what the form material is, just that
it's "newly redesigned".





Best,

Will

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

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

On Oct 22, 2006, at 7:39 AM, pentalab wrote:

#### any idiot knows you can't use Delrin rod as a form for a
roller inductor..

Oren Elliot mfg the roller inductor.

### well I guess Oren Elliot is an idiot then... so is MFJ. If
they had half a brain... they woulda known Delrin is a no-no. You
can tell it's Delrin from 8' away.... that stuff has a distinct
look about it.

Not necessarily. MFJ could have blundered on the specs
when ordering, or ignored some rated specs. I do know
that Oren Elliott changed the form though, to which type
I can't remember. You might take a look at OE's website,
seems to me they might say what it is. In other words,
they could have both blundered. This was Oren Elliots first
time of manufacturing roller inductors. They use steatite
on the air caps. Who knows, MFJ may have told Oren Elliott
that Delrin would be what to use? MFJ was the first customer
on these, and most likely was who told them they would buy
them if they made them.

Even at this, the OE products are still built better in my
opinion than some made by others as far as the other
components. Some of the cheapest stuff I've seen is by Palstar
and some stuff that MFJ made themselves such as their air caps.
The frames and brushes are pretty flimsy on them. Palstars
roller inductors are made about the same as their air caps.
Since OE changed the form material, they're the top of the line
I think.

If you dug into this, I'll about bet MFJ is who mentioned
using Delrin and hooked OE up with a plastic supplier. I just
know OE makes some pretty good air caps with a very good design.



Best,

Will

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

On Oct 22, 2006, at 4:47 PM, craxd wrote:

See below;

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

On Oct 22, 2006, at 7:39 AM, pentalab wrote:

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

wrote:

his Ameritron/ Heath/ Dentron /Amp supply/ MFJ 'engineering'

MFJ has a rather well deserved reputation as the junkiest
commercially built Hamstuff on this planet. I have heard

numerous

Hams refer to it as Mother F___ing Junk. Also, as I understand

it,

an MFJ "3000w" antenna tuner was the only one ever tested in

the

ARRL

Lab to ignite at 900W.

#### any idiot knows you can't use Delrin rod as a form for a
roller inductor..

Oren Elliot mfg the roller inductor.

Oren Elliott changed the design of the coil form using another
material after this happened. I remember e-mailing Steve Elliott
about this and he mentioned them changing it. When they designed

the

coil, they didn't check it at RF frequencies.

All they had to do is check the published D-factor for Delrin.

ABS

would have worked well around RF, but it's not as nice to turn

down

on a lathe.

I think they more or less took the suggestion from a plastics peddler
saying that Delrin would for sure work in this application. I'll have
to look up the difference in the D factor between Delrin and say
Teflon, etc. I have the Modern Plastics Encyclopedia here, I've just
not looked through it in a while.

Evidently, they didn't
have anything there to test at high power with at the time, if I
remember the conversation correctly. Anyhow, they're safe for use

now.

What material is used now?

I can't remember if he even told me what they did change it
to. Seems to me like they may mention it on their website.
Also, there's several different designs you can get on these
similar to the air variables like the brushes etc. Some cost
a little more than others according to what you order. They
also figure the buyer does the calculations to determine which
size to buy, or at least know enough to. In caps, I just told
them what model, shaft type, and air gap I wanted to place an
order. It's similar for ordering their roller inductors.

I'm pretty sure MFJ bought these direct as I used to buy direct
from them. You don't need to buy large orders either, 1-2 pieces
can be ordered.

The problem here sounds to me like MFJ continued selling the

tuners

with the delrin form inductors after knowing them to be bad. It

also

says the MFJ must have NEVER tested the tuner under full power

before

they started building them! Any good manufacturer would have

delayed

the sales and shipment until new replacement inductors could be
installed. It sounds to me like they sent them out hoping some

would

make it. The ones that didn't, simply send a new inductor and get

out

of the labor. That is unless it failed under warranty and they

had to

do the labor. It still sounds an awful lot like a bunch of penny
penching happened.

They saved pennies but they wasted dollars. That a mfg would
advertise something as "3000W" without testing it at even 900W

tells

me to avoid purchasing their products.

That's the way I seen it too!

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

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

On Oct 22, 2006, at 5:20 PM, craxd wrote:

Jim,

It's a wonder Tom didn't add a "by the way" saying, scopes and dip
meters are very inaccurate and should never be used. : ) At least

he

answered you by e-mail, he never would me.

He did not tell me this via e-mail. He said dipmeters were

worthless

during a discussion of various means of grounding grids after a
dipmeter measurement showed a result that contradicted his dicta
about grounding grids.

No, I meant I wouldn't doubt that he would have said
this to Jim.

If a scope is calibrated properly, or a dip meter the same, they
can't lie. They can only show you the truth.

That IS the problem here.

If a dip meter shows a
resonance, there is a resonance at its tuned frequency. Forget
reading the freq off the dial, simply couple it to a known

accurate

freq counter, it will show the truth if you want precision. A
calibrated scope can only show a waveform that it produces from

what

it sees at the input jack.

Correct. He didn't like the fact that an oscilloscope indicated a
worst-case potential in a SB-220 that was only about 1/3 of what

he

predicted it would be. This potential is on the verge of arcing

the

Tune-C, so even if the voltage tried to rise much higher, the cap
would zap and limit the voltage like a zener diode. The reason he
wanted the potential to be higher was to explain away what I said

was

parasitic arcing by the SB-220's occasional 110MHz oscillation.

The peak or peak to peak voltage one reads is exact, or
within the scopes calibration limits. It's according to
who calibrated it and the precision of the cal equipment
that was used, but at least < = +/- 3%.

The only way to make it lie is to not
calibrate it or set a control properly. If using a Tek or other
quality scope, your viewing something pretty accurate. I still

think

a scope is one of the better ways of measuring output power while
monitoring the signal for over-modulation and cleanliness. This
method has been used for years.

A calibrated oscilloscope is one way power meters can be

calibrated,

and it's much faster than using a bomb-calorimeter. However, an
oscilloscope is as useless as tits on a boar hog for measuring
cleanliness of a SSB signal.

Well it's according to what you term clean. Harmonics no, unless you
build or use a front end for this like the poor mans spectrum
analyzer, or one of the commercial add-on units. Over modulation,
hum, noise, regeneration, and parasitics can all be seen using a
standard scope. In the Sylvania scope book they give the following;

Modulation percentage either using the wave pattern or the trap
pattern.

Modulator output low, modulator mis-matched to RF stage.

Regen in RF stage, plus low AF output or modulator mis-match.

Low grid bias in RF stage, low excitatation, or both.

RF stage modulated incompletely neutralized.

Low excitation, low bias, or both in high-mu modulated RF stage.

Driven parasitics in modulated RF stage.

Hum modulation.

Noise modulation.

Modulation percentage or H2 - H1 / H2. H1 is the unmodulated height.

Each of the above having a distinct pattern on the scope. All can
contribute to one being un-clean.

...

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

Best,

Will

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

On Oct 24, 2006, at 1:35 AM, pentalab wrote:

### This sucks... and I don't like it one bit.

RICH SEZ... So use Matsushita/Panasonic MOFs instead of wire-wounds.

### Rich have u actually tried opening off one resistor [in a

one resistor per cap set up] and fired up the supply with a
small variac ??

RICH SEZ... Are you crazy? I was about 20-feet from where that

sucker exploded in the cal lab.

### Or should I not think about it... and hope my 24 x new

2500 > UF @ 450 V lytics don't got off like firecracker's
someday ??

RICH SEZ... To me, it sounded more like a jumbo cherry bomb.

Panasonic MOF resistors are pretty reliable.

### Flash ! with 4 x resistor's per cap... and one cut

loose. [assuming caps are no more than 75% of their v rating] The
one cap with the bad R will be almost maxed out.

RICH SEZ... That would work.

### 4 x resistor's in parallel = 25 K = lotsa heat per
cap. Probbaly 6-8 x resistor's.... each say 600-800K... all
in parallel... PER cap, would be the ultimate solution.....

then if anything opened up.... no chance of all ur caps blowing

up. The heat would be zip... per resistor.

ok problem solved.... now i can sleep

RICH SEZ.... But what if the sky falls?

later........ Jim VE7RF

########### Here's my problem Rich.... Those 2500 Uf @ 450 V CD
brand 10 A CCS ripple current rated caps I got NEW, by the case
load are listed at an unreal price tag.... like $100.00 EACH...
in single lot quantities. I have 72 of em... and will be using
em in groups of 24. I got em dirt cheap... they all tested
good, when checked on the bench. I would be just pissed if they
started exploding cuz of even the remotest chance of one resistor
lead opening.

### So... the real solution [aside from the usual 1 kv-6A safety
diode, rvs connected across eacg lytic] is to parallel 6 x 300 K
MOF resistors across EACH cap. [50 K for the paralled mess].
If one ever opened... the voltage would only increase 20% on
that one cap. Total diss is 53 W. Each of the 144 resistor's
would only dissipate .37 w. Heck, with 6 x 150 K
resistors, Total diss rises to 106 W.... or a measely .74 watt
for each of the 144 resistor's.

### For a 8000 V [no load] supply... with 24 x caps..... normal V
per cap is 333 V [74% of the 450 V max rating]. With 6 x 300K /6
x 150 K resistor's across each cap.... and say one of the 6 opened
up.... V across that one cap will increase to 400 V.......well
within the 450 V rating of the cap....... end of problem.... end of
story.

### later...... Jim VE7RF

--- In ham_amplifiers@..., Bill Turner <dezrat@...>
wrote:

ORIGINAL MESSAGE:

On Mon, 23 Oct 2006 00:20:30 -0000, "craxd" <craxd1@...>
wrote:

If a dip meter shows a
resonance, there is a resonance at its tuned frequency. Forget
reading the freq off the dial, simply couple it to a known

accurate

freq counter, it will show the truth if you want precision.

------------ REPLY FOLLOWS ------------

One needs to be careful with this. The typical single-tube or
single-transistor dip meter can be pulled considerably off the true
resonant frequency if coupling is very tight to a high-Q circuit.

Just

physically move the dip meter away far enough so the dip is barely
perceptible and the accuracy will improve greatly.

If you have used a dip meter much, you have no doubt had the
experience of tuning slowly across the dip, and as you continue

tuning

have the dip suddenly disappear as the pulling effect disappears.
Loose coupling will prevent this from happening.

### Highly agreed. Loose coupling is as good as it gets.... for
acuracy anyway. Mike Stahl, K6MYC warned me about this 25 yrs
ago.... he didn't trust em.. when tweaking yagi's.... I wouldn't
either.

### For a real laff.... I bought the "mating" grid dip osc
coils for my MFJ-259 analyzer. Two coils cover the entire
spectrum. I can't grid dip ANYTHING with em... even simple
stuff.. like a coil in parallel with a cap... on the test bench.
Then I find out nobody else can grid dip anything either! Then Rauch
sez they don't really work. They still don't. It was
suggested not to buy the optional coil(s).

### The inductance measurement is not to be trusted in a MFJ-
259-B either. Inductance measurements drop like a rock with
increasing freq. Even at 1.8 mhz.... coils will show no where
near what my B+K 875A/B does. Per Tom.... the reason is the
the stray C between turns on a coil will subtract from the coils
inductance.

### To prove that theory one way or another.... Using the
various PI spreadsheets available..[like GM3SEK's... which will
factor in the stray L of the parasitic suppressor, and all stray L
between tube and C1 cap... and also factor in the UH/XL of the RFC
[which will require an equal amount of XC... coming from the
C1 cap]. His sheet will also factor in all stray C... plus anode
to chassis of tube... in the socket.

### When the sheets say C1 should be XXX and L should be
ZZZ, and C2 should be LLL. When I use my B+K 875... and
actually measure C1 L C2... and then tie the interconnecting
straps together.... then use a resistor between anode to chassis
[to simulate the plate load Z]... and a MFJ-259 on the output....
guess what? Flat swr, or at the most... just a very tiny teak
on the C1/C2 cap to resonate.
Now the B+K operates at 1 khz... and has never let me down
yet.

### Known coils from various manufacturer's always measure dead
on with the B+K. [rare exception was this 14 uh multronics
coil used on the last project.. which measured 12.2 uh]

## If I had used the inductance measuring function of the 259-B...
at the freq under test for the simple PI [say 80/40/20m], the
resulting coil would be WAY smaller.... and of course, the C1 and
C2 values had to be INCREASED by a huge amount to compensate....
then the loaded Q is WAY up... and the resulting circulating
currents are way up.

### Moral of the story.... use a MFJ-259B to measure inductance
for anything... like PI nets, LC networks, you name it... and you
will be guaranteed 100%, to have complete failure. Get a real LCR
meter. If you can't measure L + C accurately..[that's 90% of
radio].... you are dead in the water.

Later...... Jim VE7RF

Bill, W6WRT

ORIGINAL MESSAGE:

On Mon, 23 Oct 2006 00:20:30 -0000, "craxd" <craxd1@...>
wrote:

If a dip meter shows a
resonance, there is a resonance at its tuned frequency. Forget
reading the freq off the dial, simply couple it to a known accurate
freq counter, it will show the truth if you want precision.

------------ REPLY FOLLOWS ------------

One needs to be careful with this. The typical single-tube or
single-transistor dip meter can be pulled considerably off the true
resonant frequency if coupling is very tight to a high-Q circuit. Just
physically move the dip meter away far enough so the dip is barely
perceptible and the accuracy will improve greatly.

If you have used a dip meter much, you have no doubt had the
experience of tuning slowly across the dip, and as you continue tuning
have the dip suddenly disappear as the pulling effect disappears.
Loose coupling will prevent this from happening.

Bill, W6WRT

Well, by some means Yahoo removed the text I wrote after my "Read this:" statement and before my sign. What I suggested to DJ7SW was to read the very bottom of the message, where there are instructions to unsubscribe from the list and group.

Best regards
Guillermo - LU8EYW.

GGLL escribi:

On Oct 24, 2006, at 5:25 AM, GGLL wrote:

R L Measures escribió:

On Oct 24, 2006, at 1:35 AM, pentalab wrote:

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

On Oct 23, 2006, at 3:23 PM, GGLL wrote:

**** I have changed the subject ****

Please see below:

R L Measures escribió:

...
Hello Rich, how fast (or slow) you think voltage will rise
in the capacitor with its bleeder open?.

Probably about as fast as the capacitors with resistors discharge.

One could think that the losses of the capacitor could
be considered as "resistance", but of very high value, so
applying plain
voltage divider equations the higher potential will be there.

###### Exactly my thoughts. That's the only explanation that
works.

The fly in the pie is that the leakage R of the C is changing.

With voltage? or because of own unstable characteristics?.

Correctomundo. When the potential on the 200uF, 500wvdc electrolytic
with the open bleeder/equalizer R goes above 500v, leakage-I as well
as heating increases exponentially and the fireworks show is about to
start

### Rich have u actually tried opening off one resistor [in a one
resistor per cap set up] and fired up the supply with a small
variac ??

Are you crazy? I was about 20-feet from where that sucker exploded
in the cal lab.

Perhaps scaling down components (voltage specially, seriously
talking) and
being at a safe distance (100 mtrs or so) with remote measuring and
a robot
turning on the whole thing (not seriously talking)....

chortle

But what if the sky falls?

That's the only thing that worries Asterix and his chief.

guffaw

cheers, Guillermo

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

On Oct 24, 2006, at 4:57 AM, Tony King - W4ZT wrote:

R L Measures wrote:
<snip>

### Lemmee ask u this Rich..... IF u were gonna build a HB 2 x 3-
500Z linear from scratch... would u use the 3 x 200 pf caps [ or
any othwer value] or not ??????????????????

I would use: 1500 - 2000 pF total per socket consisting of three
different values per each, a grid fusing element, a FWD/FWB
switchable PS, and I would use a glitch R, followed by an 8160.

<snip>
Rich, he asked about a pair of 3-500Z's... but, since you mentioned the
8160, do you mean you would NOT directly ground the grid of the 8160 and
put a fusing element between B- and ground?

The 3-500Zs would be the buffer amplifier, and the 8160 would be the final amplifier. With the latter, as you realized, since the grid is grounded by its socket, a grid fusing device would have to go between the grid-I meter shunt and gnd. Overall power gain would be c. 200x, which is about the same as an 8281 tetrode in AB1.

cheers, Tony.

73, Tony W4ZT

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