As promised, I put together a simple test jig to measure leakage across
vintage capacitors, particularly "bumblebees." I didn't test all that I
had, just a small sample, but the results were consistent.

The jig consisted of a variable 0-400 VDC power supply, I connected a test
capacitor in series with a 1K 2W resistor, and measured the voltage
generated across the resistor with a DVM.

Group #1 (Bumblebee). 400V devices.

#1 Nominal 47 nF, measured 68 nF. At 400V leakage was 1.13V after a couple
of minutes and continued to rise with time. The cap generated heat, as
expected.

#2 Nominal 47 nF, measured 72 nF. At 400V leakage was 1.2V after a few
minutes and rising.

#3 Nominal 47 nF, measured 65 nF. Tested at 200 V. Began at 35 mV and
continued to rise.

Group #2 (Bumblebee) 200V devices

#4 Nominal 33 nF, measured 55 nF. Tested @ 200V. Initial leakage of
0.482V steadily decreasing with time. No perceptible heating.

#5 Nominal 12 nF, measured 13 nF. Tested at 200V. Initial leakage of 2.5
mV, decreased to 1.56 mV after about 5 minutes. No heating discerned.

For comparison purposes, I tested a Sprague .2 uF 600V cap of the same
vintage (the same brand used to couple the output stage of a McIntosh
MC240). There was no leakage voltage measured @ 400V.

Dumont .15 uF 600V cap from Acrosound amplifier (late 50s or early 60s).
Measured only 0.1 mV. Stable.

Conclusions:

Based upon my small sample group, the folks who said the Bumblebees leak are
correct! Presumably the 47 nF caps would eventually self-destruct. The
lesser value caps decreased leakage voltage with time and it would be
interesting to do a longer term test.

The Sprague and Dumonts were still good after all of these years.

I realize this is more of a qualitative than quantitative test, but it still
should be useful info.

Jon Yaeger

"Jon Yaeger" wrote in message
...

As promised, I put together a simple test jig to measure leakage across
vintage capacitors, particularly "bumblebees." I didn't test all that I
had, just a small sample, but the results were consistent.

The jig consisted of a variable 0-400 VDC power supply, I connected a
test
capacitor in series with a 1K 2W resistor, and measured the voltage
generated across the resistor with a DVM.

Group #1 (Bumblebee). 400V devices.

#1 Nominal 47 nF, measured 68 nF. At 400V leakage was 1.13V after a
couple
of minutes and continued to rise with time. The cap generated heat, as
expected.

#2 Nominal 47 nF, measured 72 nF. At 400V leakage was 1.2V after a few
minutes and rising.

#3 Nominal 47 nF, measured 65 nF. Tested at 200 V. Began at 35 mV and
continued to rise.

Group #2 (Bumblebee) 200V devices

#4 Nominal 33 nF, measured 55 nF. Tested @ 200V. Initial leakage of
0.482V steadily decreasing with time. No perceptible heating.

#5 Nominal 12 nF, measured 13 nF. Tested at 200V. Initial leakage of
2.5
mV, decreased to 1.56 mV after about 5 minutes. No heating discerned.

For comparison purposes, I tested a Sprague .2 uF 600V cap of the same
vintage (the same brand used to couple the output stage of a McIntosh
MC240). There was no leakage voltage measured @ 400V.

Dumont .15 uF 600V cap from Acrosound amplifier (late 50s or early 60s).
Measured only 0.1 mV. Stable.

Conclusions:

Based upon my small sample group, the folks who said the Bumblebees leak
are
correct! Presumably the 47 nF caps would eventually self-destruct. The
lesser value caps decreased leakage voltage with time and it would be
interesting to do a longer term test.

The Sprague and Dumonts were still good after all of these years.

I realize this is more of a qualitative than quantitative test, but it
still
should be useful info.

Jon Yaeger

Thanks for the heads up, Jon
west

"Jon Yaeger" wrote in message
...

As promised, I put together a simple test jig to measure leakage across
vintage capacitors, particularly "bumblebees." I didn't test all that I
had, just a small sample, but the results were consistent.

The jig consisted of a variable 0-400 VDC power supply, I connected a
test
capacitor in series with a 1K 2W resistor, and measured the voltage
generated across the resistor with a DVM.

Group #1 (Bumblebee). 400V devices.

#1 Nominal 47 nF, measured 68 nF. At 400V leakage was 1.13V after a
couple
of minutes and continued to rise with time. The cap generated heat, as
expected.

#2 Nominal 47 nF, measured 72 nF. At 400V leakage was 1.2V after a few
minutes and rising.

#3 Nominal 47 nF, measured 65 nF. Tested at 200 V. Began at 35 mV and
continued to rise.

Group #2 (Bumblebee) 200V devices

#4 Nominal 33 nF, measured 55 nF. Tested @ 200V. Initial leakage of
0.482V steadily decreasing with time. No perceptible heating.

#5 Nominal 12 nF, measured 13 nF. Tested at 200V. Initial leakage of
2.5
mV, decreased to 1.56 mV after about 5 minutes. No heating discerned.

For comparison purposes, I tested a Sprague .2 uF 600V cap of the same
vintage (the same brand used to couple the output stage of a McIntosh
MC240). There was no leakage voltage measured @ 400V.

Dumont .15 uF 600V cap from Acrosound amplifier (late 50s or early 60s).
Measured only 0.1 mV. Stable.

Conclusions:

Based upon my small sample group, the folks who said the Bumblebees leak
are
correct! Presumably the 47 nF caps would eventually self-destruct. The
lesser value caps decreased leakage voltage with time and it would be
interesting to do a longer term test.

The Sprague and Dumonts were still good after all of these years.

I realize this is more of a qualitative than quantitative test, but it
still
should be useful info.

Jon Yaeger

Jon, It is surprising that you got around to this test.

For comparison why don't you test some plastic caps with no paper in them.
They should show no leakage at all.

The 400V test on the 600V cap probably makes it look better than it really
is.

Must make this reply short. Something strange has happened to this
computer. The backspace key and the forward space key have traded
functions. I have reinstalled everything including OS. As a last resort
I'll wiggle the keyboard plug in the socket. If that isn't it, then I'll
have get used it. Mabey it is the keyboard. Typing is tedious.

Thanks for the interesting post, Jon. Mark

Jon, I had accidentally pushed ctrl+alt+shift+backspace and put the keyboard
in lefthanded mode. I turned the keyboard over to unscrew the bottom and
there was the sticker. I reply below.
"Jon Yaeger" wrote in message
...

As promised, I put together a simple test jig to measure leakage across
vintage capacitors, particularly "bumblebees." I didn't test all that I
had, just a small sample, but the results were consistent.

I found a whole bag of new Sprague black beauties, but I haven't tested them
yet.

The jig consisted of a variable 0-400 VDC power supply, I connected a
test
capacitor in series with a 1K 2W resistor, and measured the voltage
generated across the resistor with a DVM.

Group #1 (Bumblebee). 400V devices.

#1 Nominal 47 nF, measured 68 nF. At 400V leakage was 1.13V after a
couple
of minutes and continued to rise with time. The cap generated heat, as
expected.

Doesn't seem like 1.13mA would generate any heat. These old things don't
seem to short out so much as just leak bias current. The impregnant (wax
compound) deteriorates so they are probably going to keep changing.

#2 Nominal 47 nF, measured 72 nF. At 400V leakage was 1.2V after a few
minutes and rising.

The capacitance change is worse than the leakage. I have had to scrape old
paper shell gooballs off of a chassis before. They just melted and stuck to
the floor. Mabey it was heat. The customer would say that it didn't work
anymore. The caps were still there, but they didn't burn up.

#3 Nominal 47 nF, measured 65 nF. Tested at 200 V. Began at 35 mV and
continued to rise.

Group #2 (Bumblebee) 200V devices

#4 Nominal 33 nF, measured 55 nF. Tested @ 200V. Initial leakage of
0.482V steadily decreasing with time. No perceptible heating.

#5 Nominal 12 nF, measured 13 nF. Tested at 200V. Initial leakage of
2.5
mV, decreased to 1.56 mV after about 5 minutes. No heating discerned.


For comparison purposes, I tested a Sprague .2 uF 600V cap of the same
vintage (the same brand used to couple the output stage of a McIntosh
MC240). There was no leakage voltage measured @ 400V.

A good cap will take considerable overvoltage. The leakage in these old
ones will often increase drastically with just a bit of overvolt.


Dumont .15 uF 600V cap from Acrosound amplifier (late 50s or early 60s).
Measured only 0.1 mV. Stable.

Conclusions:

Based upon my small sample group, the folks who said the Bumblebees leak
are
correct! Presumably the 47 nF caps would eventually self-destruct.

I have never seen one destroyed by shorting out. They seem to just open up,
for lack of a better description. They don't seem to short like a plastic
or electrolytic. They just decompose and turn from cap into gooball, the
paper cased ones that is.

When I fix old record changers sometimes the grease will decompose and
literally
corrode the galvanized metal. Maybe the impregnant decomposes to the point
that it starts attacking the metal foil.

The
lesser value caps decreased leakage voltage with time and it would be
interesting to do a longer term test.

Get some more power supplies and put them in series to get about 625V. I
tested a whole bunch of these paper caps, all kinds. The only ones that
weren't bad were the VitaminQs and some of the hermetically sealed ones.
Paper/mylar seems to holds up real well. Sprague 118s have paper/mylar and
also wax. I have some of them I am going to test for leakage, sometime.

The Sprague and Dumonts were still good after all of these years.

The different companies had different and often proprietary impregnants.
Some of them lasted a lot longer.

I realize this is more of a qualitative than quantitative test, but it
still
should be useful info.

Put rated voltage across them to test them. They will probably be OK for
many years at
reduced working voltage. Mabey the reason they used 600V caps in 160V
circuits is because they knew they would degrade.

I was looking at a Rifa catalog and saw some paper/resin across the line
caps that are currently in production. They probably last a very long time
and may have the traditional paper sound.

http://www.evox-rifa.com/cap_catalog...pr/pme271y.pdf

metallized paper RFI caps. PME271 is a part number. "impregnated and
encased in epoxy resin". Mark

Jon Yaeger

in article , truegridtz at
wrote on 6/21/05 3:05 AM:


"Jon Yaeger" wrote in message
...

As promised, I put together a simple test jig to measure leakage across
vintage capacitors, particularly "bumblebees." I didn't test all that I
had, just a small sample, but the results were consistent.

The jig consisted of a variable 0-400 VDC power supply, I connected a
test
capacitor in series with a 1K 2W resistor, and measured the voltage
generated across the resistor with a DVM.

Group #1 (Bumblebee). 400V devices.

#1 Nominal 47 nF, measured 68 nF. At 400V leakage was 1.13V after a
couple
of minutes and continued to rise with time. The cap generated heat, as
expected.

#2 Nominal 47 nF, measured 72 nF. At 400V leakage was 1.2V after a few
minutes and rising.

#3 Nominal 47 nF, measured 65 nF. Tested at 200 V. Began at 35 mV and
continued to rise.

Group #2 (Bumblebee) 200V devices

#4 Nominal 33 nF, measured 55 nF. Tested @ 200V. Initial leakage of
0.482V steadily decreasing with time. No perceptible heating.

#5 Nominal 12 nF, measured 13 nF. Tested at 200V. Initial leakage of
2.5
mV, decreased to 1.56 mV after about 5 minutes. No heating discerned.

For comparison purposes, I tested a Sprague .2 uF 600V cap of the same
vintage (the same brand used to couple the output stage of a McIntosh
MC240). There was no leakage voltage measured @ 400V.

Dumont .15 uF 600V cap from Acrosound amplifier (late 50s or early 60s).
Measured only 0.1 mV. Stable.

Conclusions:

Based upon my small sample group, the folks who said the Bumblebees leak
are
correct! Presumably the 47 nF caps would eventually self-destruct. The
lesser value caps decreased leakage voltage with time and it would be
interesting to do a longer term test.

The Sprague and Dumonts were still good after all of these years.

I realize this is more of a qualitative than quantitative test, but it
still
should be useful info.

Jon Yaeger

Jon, It is surprising that you got around to this test.

*** Gee, I try to do what I promise!

For comparison why don't you test some plastic caps with no paper in them.
They should show no leakage at all.

*** Some day I'd like to publish results of various brands, using a more
rigorous test.

The 400V test on the 600V cap probably makes it look better than it really
is.

*** Yes, I know. A limitation of my 400V supply . . . .

Must make this reply short. Something strange has happened to this
computer. The backspace key and the forward space key have traded
functions. I have reinstalled everything including OS. As a last resort
I'll wiggle the keyboard plug in the socket. If that isn't it, then I'll
have get used it. Mabey it is the keyboard. Typing is tedious.

*** I've seen viruses do this. Download the free file monitor program,
Hijack This and see what's being loaded on your PC. Look especially at
browser helper objects (BHOs) and delete anything you can't readily
identify. I can e-mail you the program if you can't find it.

Thanks for the interesting post, Jon. Mark

*** You're welcome!

in article , truegridtz at
wrote on 6/21/05 4:09 AM:

Jon, I had accidentally pushed ctrl+alt+shift+backspace and put the keyboard
in lefthanded mode. I turned the keyboard over to unscrew the bottom and
there was the sticker. I reply below.
"Jon Yaeger" wrote in message
...

As promised, I put together a simple test jig to measure leakage across
vintage capacitors, particularly "bumblebees." I didn't test all that I
had, just a small sample, but the results were consistent.

I found a whole bag of new Sprague black beauties, but I haven't tested them
yet.

The jig consisted of a variable 0-400 VDC power supply, I connected a
test
capacitor in series with a 1K 2W resistor, and measured the voltage
generated across the resistor with a DVM.

Group #1 (Bumblebee). 400V devices.

#1 Nominal 47 nF, measured 68 nF. At 400V leakage was 1.13V after a
couple
of minutes and continued to rise with time. The cap generated heat, as
expected.

Doesn't seem like 1.13mA would generate any heat. These old things don't
seem to short out so much as just leak bias current. The impregnant (wax
compound) deteriorates so they are probably going to keep changing.

*** Note that's 1.13 VOLTS, not millivolts!

#2 Nominal 47 nF, measured 72 nF. At 400V leakage was 1.2V after a few
minutes and rising.

The capacitance change is worse than the leakage. I have had to scrape old
paper shell gooballs off of a chassis before. They just melted and stuck to
the floor. Mabey it was heat. The customer would say that it didn't work
anymore. The caps were still there, but they didn't burn up.

*** I've never seen catastrophic US coupling cap failure. Japanese
products are another story.

#3 Nominal 47 nF, measured 65 nF. Tested at 200 V. Began at 35 mV and
continued to rise.

Group #2 (Bumblebee) 200V devices

#4 Nominal 33 nF, measured 55 nF. Tested @ 200V. Initial leakage of
0.482V steadily decreasing with time. No perceptible heating.

#5 Nominal 12 nF, measured 13 nF. Tested at 200V. Initial leakage of
2.5
mV, decreased to 1.56 mV after about 5 minutes. No heating discerned.


For comparison purposes, I tested a Sprague .2 uF 600V cap of the same
vintage (the same brand used to couple the output stage of a McIntosh
MC240). There was no leakage voltage measured @ 400V.

A good cap will take considerable overvoltage. The leakage in these old
ones will often increase drastically with just a bit of overvolt.

*** Good point, and worthy of confirmation.


Dumont .15 uF 600V cap from Acrosound amplifier (late 50s or early 60s).
Measured only 0.1 mV. Stable.

Conclusions:

Based upon my small sample group, the folks who said the Bumblebees leak
are
correct! Presumably the 47 nF caps would eventually self-destruct.

I have never seen one destroyed by shorting out. They seem to just open up,
for lack of a better description. They don't seem to short like a plastic
or electrolytic. They just decompose and turn from cap into gooball, the
paper cased ones that is.

When I fix old record changers sometimes the grease will decompose and
literally
corrode the galvanized metal. Maybe the impregnant decomposes to the point
that it starts attacking the metal foil.

The
lesser value caps decreased leakage voltage with time and it would be
interesting to do a longer term test.

Get some more power supplies and put them in series to get about 625V. I
tested a whole bunch of these paper caps, all kinds. The only ones that
weren't bad were the VitaminQs and some of the hermetically sealed ones.
Paper/mylar seems to holds up real well. Sprague 118s have paper/mylar and
also wax. I have some of them I am going to test for leakage, sometime.

The Sprague and Dumonts were still good after all of these years.

The different companies had different and often proprietary impregnants.
Some of them lasted a lot longer.

I realize this is more of a qualitative than quantitative test, but it
still
should be useful info.

Put rated voltage across them to test them. They will probably be OK for
many years at
reduced working voltage. Mabey the reason they used 600V caps in 160V
circuits is because they knew they would degrade.

I was looking at a Rifa catalog and saw some paper/resin across the line
caps that are currently in production. They probably last a very long time
and may have the traditional paper sound.

http://www.evox-rifa.com/cap_catalog...pr/pme271y.pdf

metallized paper RFI caps. PME271 is a part number. "impregnated and
encased in epoxy resin". Mark

*** Thanks, good to know.

Jon Yaeger

in article
,
Mark Harriss at wrote on 6/22/05 12:25 AM:

These are wax paper ones John?,

*** I believe so, but I haven't dissected one to confirm.


what happens if you
bake one for a while, or if you had a vac pump and
evacuated one for a few hours?.

*** Dunno. Interesting experiment. Don't think it would have much
relevance for their (possible) intended re-use in audio gear, where the only
vacuums are inside of the valves and the baking would be a function of on
time and convection . . . . ;-)

Regards
Mark Harriss

Jon Yaeger wrote:


*** Dunno. Interesting experiment. Don't think it would have much
relevance for their (possible) intended re-use in audio gear, where the only
vacuums are inside of the valves and the baking would be a function of on
time and convection . . . . ;-)


The vacuum would remove any adsorbed water without heating the cap
even transformaer oil will pick up water from the atmosphere and
would need heating or vacuum to remove it.

Regards
Mark

in article
,
Mark Harriss at wrote on 6/21/05 8:52 AM:

Jon Yaeger wrote:


*** Dunno. Interesting experiment. Don't think it would have much
relevance for their (possible) intended re-use in audio gear, where the only
vacuums are inside of the valves and the baking would be a function of on
time and convection . . . . ;-)


The vacuum would remove any adsorbed water without heating the cap
even transformaer oil will pick up water from the atmosphere and
would need heating or vacuum to remove it.

Regards
Mark


Mark,

I understand your rationale for doing the experiment.

Two things come to mind and hence the reason for my reply:

#1 If we were able to dehydrate the cap, performance over time would be
interesting and useful. In other words, how much additional life expectancy
or increase in performance would result (if any), and for how long?

#2 Any cap dehydrated in that manner and put back into audio service would
be subject to re-degradation by exposure to humidity & normal atmospheric
conditions.

If caps were to improve for long periods after dehydration, another facet of
"amp restoration" might involve a spell in a vacuum chamber . . . . .


Jon

Jon, .


#1 Nominal 47 nF, measured 68 nF. At 400V leakage was 1.13V after a
couple
of minutes and continued to rise with time. The cap generated heat, as
expected.

Doesn't seem like 1.13mA would generate any heat. These old things
don't
seem to short out so much as just leak bias current. The impregnant
(wax
compound) deteriorates so they are probably going to keep changing.

*** Note that's 1.13 VOLTS, not millivolts!

Yes, and 1.3 divided by 1000 ohms yields 1.13mA. This much current going
through a resistance using up 400V generates about .45 watts of heat.
Now I see why some of your test specimens got warm. This is most probably
why the paper shell caps fall apart. They do get hot inside.

I went ahead and tested some of the paper caps I have. I'll try to post the
results before the thread gets forgotten.

My second power supply (to bring the 470V PS up to about 630V has a blown
regulator.) I am going to try to string out some other ones to get 600V.

The tests I did were all for up to 400V caps.

Evidently I have already tested these paper caps years ago and discarded all
of the bad ones. Almost all of these are hermetically sealed and still good
except the
Sprague Black Beauties.

The Sprague Black Beauties that I have are all 600V.

Sometime between 1956 and 1973 Sprague changed their black beauties from
TELECAP to DIFILM on the inside. Same dimensions for the cases. The
Telecaps were paper and wax and the Difilm were paper+mylar+wax.

So, these 600V Difilms that I have here (they have orange printing on them)
may still be good. I know they are Difilms because the part numbers are a
bit different for some of them. They added a zero to the values that ended
in a zero.

For example a 6TM-S3 Telecap became a 6TM-S30 Difilm. The Difilms also have
160P on them because the Difilms had a new part number, at last some of them
did. I hate to break of specimens because they are probably getting rare.

The Telecaps were impregnated with oil for values 600V upto 1600V. The
Difilms are all solid impregnant.

Evidently a Sprague 118 Difilm is a black beauty with a metal package,
hermetically sealed. I did have some of them at 200 and 400V. They tested
OK, but not ideal.

Does, the plastic case Difilm hold up to moisture impregnation? This is
what a 600V power supply will reveal. Do they hold up as well as the 118?

There are some McIntosh Sam's. The parts substitution chart may reveal who
made the bumblebees.

I'll try to get the test finished. If I don't do it now it will probably
never get done. Mark

I was looking at a Rifa catalog and saw some paper/resin across the line
caps that are currently in production. They probably last a very long time
and may have the traditional paper sound.


I tried that. Too leaky for use as coupling caps in tube
amps. Leakage is not much of an issue across the line.
Their main feature is that they "self heal" when a spot
inside does start to short out (burns itself clear).

The vacuum would remove any adsorbed water without heating the cap
even transformaer oil will pick up water from the atmosphere and
would need heating or vacuum to remove it.


I don't think that this will help any. The moisture that gets
into the paper cap will react with the acid in the paper and
degrade it. I don't think that it's reversible. Replace the
cap.

Mark Harriss wrote:

These are wax paper ones John?, what happens if you
bake one for a while, or if you had a vac pump and
evacuated one for a few hours?.

Dielectric failure is not mended by dehydration. Also, in commercial
gear I encounter many split-open oil versions. It isn't clear whether
they fractured from severe environmental changes (such as being in a
New England barn for 30 years) or from electrial failure, or both.

The one in my 1959 guitar, having never been freeze-thaw cycled nor had
any exposure to significant voltage, is still perfect.

"robert casey" wrote in message
ink.net...

I was looking at a Rifa catalog and saw some paper/resin across the line
caps that are currently in production. They probably last a very long
time
and may have the traditional paper sound.


I tried that. Too leaky for use as coupling caps in tube
amps. Leakage is not much of an issue across the line.
Their main feature is that they "self heal" when a spot
inside does start to short out (burns itself clear).

Robert,


First of all, why would an across-the -line cap leak? They are the same
dielectrics. The self-healing aspect is common among metallized caps and
is not unique to ATL caps. I tested a few. They don't leak. The RIFAs are
rated at 1000VDC. Why would they leak? Mark

Top Post:

Here are the results of the tests on various paper and paper+mylar caps.
Most made after 1970. I had wanted to see how they held up at large
over-voltages. This seemed like a good time to test them.

I went through them a few years ago and discarded all known defective caps.
So, these were the ones that were still good for audio.

A 1K resistor in series with the cap in addition to a uA (microamp) DVM
in-line were used to monitor leakage. The uA DVM and the mV DVM (across the
1K) agreed at all times. The mV scale measured down to tenths of a mV. An
interrupt switch was placed in the path to interrupt the load and see how
much current the mV meter was passing.

The 600V Sprague Difilm black beauties don't leak at 630V. I broke one open
and they don't have oil like the old generation Telecap black beauty. They
are also of inferior construction in general. The terminations are held in
place by the plastic case. The lead is only touching a wad of foil.

Sprague 118 (hermetically sealed difilm) was similar to Difilm black
beauty. 200V cap taken to 275V for test. No leakage detected.

Sprague Vitamin-Q were tested at a voltage of over 150% of rated voltage.
No leakage found.

Various "CP" military papers were tested. All showed no leakage at voltages
over rated voltage. I could only take a 600V cap to 640V. The 200,300, and
400V CPs were taken to at least 150% of rated V.

The only leaky caps we
(1) CDE BlackCat (paper+mylar) which showed about .3uA at 630V
(2) CDE Cub -paper and impregnant - a 200V cap leaked 70uA at 35V so I
stopped the test there.

Almost all bumblebees and other wax+paper caps were discarded years ago.
They leaked terribly.

Perhaps some of the bumblebees are paper+mylar and thus still useable. Mark



"truegridtz" wrote in message
...
Jon, .


#1 Nominal 47 nF, measured 68 nF. At 400V leakage was 1.13V after a
couple
of minutes and continued to rise with time. The cap generated heat,
as
expected.

Doesn't seem like 1.13mA would generate any heat. These old things
don't
seem to short out so much as just leak bias current. The impregnant
(wax
compound) deteriorates so they are probably going to keep changing.

*** Note that's 1.13 VOLTS, not millivolts!

Yes, and 1.3 divided by 1000 ohms yields 1.13mA. This much current going
through a resistance using up 400V generates about .45 watts of heat.
Now I see why some of your test specimens got warm. This is most probably
why the paper shell caps fall apart. They do get hot inside.

I went ahead and tested some of the paper caps I have. I'll try to post
the
results before the thread gets forgotten.

My second power supply (to bring the 470V PS up to about 630V has a blown
regulator.) I am going to try to string out some other ones to get 600V.

The tests I did were all for up to 400V caps.

Evidently I have already tested these paper caps years ago and discarded
all
of the bad ones. Almost all of these are hermetically sealed and still
good
except the
Sprague Black Beauties.

The Sprague Black Beauties that I have are all 600V.

Sometime between 1956 and 1973 Sprague changed their black beauties from
TELECAP to DIFILM on the inside. Same dimensions for the cases. The
Telecaps were paper and wax and the Difilm were paper+mylar+wax.

So, these 600V Difilms that I have here (they have orange printing on
them)
may still be good. I know they are Difilms because the part numbers are a
bit different for some of them. They added a zero to the values that
ended
in a zero.

For example a 6TM-S3 Telecap became a 6TM-S30 Difilm. The Difilms also
have
160P on them because the Difilms had a new part number, at last some of
them
did. I hate to break of specimens because they are probably getting rare.

The Telecaps were impregnated with oil for values 600V upto 1600V. The
Difilms are all solid impregnant.

Evidently a Sprague 118 Difilm is a black beauty with a metal package,
hermetically sealed. I did have some of them at 200 and 400V. They
tested
OK, but not ideal.

Does, the plastic case Difilm hold up to moisture impregnation? This is
what a 600V power supply will reveal. Do they hold up as well as the 118?

There are some McIntosh Sam's. The parts substitution chart may reveal
who
made the bumblebees.

I'll try to get the test finished. If I don't do it now it will probably
never get done. Mark

These are wax paper ones John?, what happens if you
bake one for a while, or if you had a vac pump and
evacuated one for a few hours?.

Regards
Mark Harriss

http://www.vacuumtube.com/capacito.htm

Check out these prices for paper caps. I broke open an $18 black beauty
just to see what was inside. Mark

Casual bumblebee capacitor test... as opposed to capacitors being
tested by a bumblebee in a suit.

Sorry, I couldn't resist ;-)

wrote:
Casual bumblebee capacitor test... as opposed to capacitors being
tested by a bumblebee in a suit.

Sorry, I couldn't resist ;-)



No ...thats's a "formal" bumblebee test

Mark Harriss wrote:

wrote:
Casual bumblebee capacitor test... as opposed to capacitors being
tested by a bumblebee in a suit.

Sorry, I couldn't resist ;-)


No ...thats's a "formal" bumblebee test

There are some suitable flame suits for aforersaid bumblebee
being auctioned at http://www.ebay.com/items/suits/flamers/small.

Coaxing the bumblebee to put on such mini suits is a real PITA,
let alone coaxing the insect to go into a tube amp to test high voltages

across capacitors. They get quite cross if they get an electric shock.

Patrick Turner.

For the record, just to be fair, the comment below about the Difilm
Bumblebee being of inferior construction is WRONG. Reinspection revealed
that the leads are soldered to the foil tabs like most any other capacitor.

They came off quite easily, but they were soldered to the foil very
completely. Mark
"truegridtz" wrote in message
...
Top Post:

Here are the results of the tests on various paper and paper+mylar caps.
Most made after 1970. I had wanted to see how they held up at large
over-voltages. This seemed like a good time to test them.

I went through them a few years ago and discarded all known defective
caps.
So, these were the ones that were still good for audio.

A 1K resistor in series with the cap in addition to a uA (microamp) DVM
in-line were used to monitor leakage. The uA DVM and the mV DVM (across
the
1K) agreed at all times. The mV scale measured down to tenths of a mV.
An
interrupt switch was placed in the path to interrupt the load and see how
much current the mV meter was passing.

The 600V Sprague Difilm black beauties don't leak at 630V. I broke one
open
and they don't have oil like the old generation Telecap black beauty.
They
are also of inferior construction in general. The terminations are held
in
place by the plastic case. The lead is only touching a wad of foil.

Sprague 118 (hermetically sealed difilm) was similar to Difilm black
beauty. 200V cap taken to 275V for test. No leakage detected.

Sprague Vitamin-Q were tested at a voltage of over 150% of rated voltage.
No leakage found.

Various "CP" military papers were tested. All showed no leakage at
voltages
over rated voltage. I could only take a 600V cap to 640V. The 200,300,
and
400V CPs were taken to at least 150% of rated V.

The only leaky caps we
(1) CDE BlackCat (paper+mylar) which showed about .3uA at 630V
(2) CDE Cub -paper and impregnant - a 200V cap leaked 70uA at 35V so I
stopped the test there.

Almost all bumblebees and other wax+paper caps were discarded years ago.
They leaked terribly.

Perhaps some of the bumblebees are paper+mylar and thus still useable.
Mark



"truegridtz" wrote in message
...
Jon, .


#1 Nominal 47 nF, measured 68 nF. At 400V leakage was 1.13V after
a
couple
of minutes and continued to rise with time. The cap generated
heat,
as
expected.

Doesn't seem like 1.13mA would generate any heat. These old things
don't
seem to short out so much as just leak bias current. The impregnant
(wax
compound) deteriorates so they are probably going to keep changing.

*** Note that's 1.13 VOLTS, not millivolts!

Yes, and 1.3 divided by 1000 ohms yields 1.13mA. This much current
going
through a resistance using up 400V generates about .45 watts of heat.
Now I see why some of your test specimens got warm. This is most
probably
why the paper shell caps fall apart. They do get hot inside.

I went ahead and tested some of the paper caps I have. I'll try to post
the
results before the thread gets forgotten.

My second power supply (to bring the 470V PS up to about 630V has a
blown
regulator.) I am going to try to string out some other ones to get
600V.

The tests I did were all for up to 400V caps.

Evidently I have already tested these paper caps years ago and discarded
all
of the bad ones. Almost all of these are hermetically sealed and still
good
except the
Sprague Black Beauties.

The Sprague Black Beauties that I have are all 600V.

Sometime between 1956 and 1973 Sprague changed their black beauties from
TELECAP to DIFILM on the inside. Same dimensions for the cases. The
Telecaps were paper and wax and the Difilm were paper+mylar+wax.

So, these 600V Difilms that I have here (they have orange printing on
them)
may still be good. I know they are Difilms because the part numbers are
a
bit different for some of them. They added a zero to the values that
ended
in a zero.

For example a 6TM-S3 Telecap became a 6TM-S30 Difilm. The Difilms also
have
160P on them because the Difilms had a new part number, at last some of
them
did. I hate to break of specimens because they are probably getting
rare.

The Telecaps were impregnated with oil for values 600V upto 1600V. The
Difilms are all solid impregnant.

Evidently a Sprague 118 Difilm is a black beauty with a metal package,
hermetically sealed. I did have some of them at 200 and 400V. They
tested
OK, but not ideal.

Does, the plastic case Difilm hold up to moisture impregnation? This is
what a 600V power supply will reveal. Do they hold up as well as the
118?

There are some McIntosh Sam's. The parts substitution chart may reveal
who
made the bumblebees.

I'll try to get the test finished. If I don't do it now it will
probably
never get done. Mark