Checking leaky caps
 

I always heard about leaky caps being a problem with boatanchors, other than
checking for the capacitor value is there a way to check if its a "leaky
cap" using just a multitester or voltmeter?

Thanks.....gil

gil wrote:
I always heard about leaky caps being a problem with boatanchors, other than
checking for the capacitor value is there a way to check if its a "leaky
cap" using just a multitester or voltmeter?

Thanks.....gil


There's some good capacitor testers around but as a rule on older BAs
(30s-40s) if it doesn't pass an ohmmeter test you need not go any
further. I chuck anything over about 1 Meg of leakage which tends to be
most all wax/paper caps from that era.
The digital voltmeters often have a capacitance test function but are
thrown off in the presence of leakage. Again, if it doesn't measure
right, out she goes.
The problem is due to the breakdown of the paper dielectric inside. For
the most part thats inevitable in spite of how well sealed it is. Some
of the high-end mil-spec metal cased guys have survived but thats about
all. The rest are hit-and-miss.
In later gear, say the 50s, the "good" rate is much improved but certain
types like the banded black beauties are notoriously bad as are those
pink plastic ones found in 50s/60s Hallicrafters gear.
The debate lingers on just how much performance degradation and
reliability can be tolerated since the bad caps may not have a
particular detrimental effect *today* depending on where in the circuit
they are used. I suppose it depends whether or not you are "restoring"
or "repairing".
I cross-posted this to rec.antiques.radio+phono so you could catch some
other opinions.
Good luck!
-Bill

gil wrote:
I always heard about leaky caps being a problem with boatanchors, other than
checking for the capacitor value is there a way to check if its a "leaky
cap" using just a multitester or voltmeter?

Thanks.....gil


There's some good capacitor testers around but as a rule on older BAs
(30s-40s) if it doesn't pass an ohmmeter test you need not go any
further. I chuck anything over about 1 Meg of leakage which tends to be
most all wax/paper caps from that era.
The digital voltmeters often have a capacitance test function but are
thrown off in the presence of leakage. Again, if it doesn't measure
right, out she goes.
The problem is due to the breakdown of the paper dielectric inside. For
the most part thats inevitable in spite of how well sealed it is. Some
of the high-end mil-spec metal cased guys have survived but thats about
all. The rest are hit-and-miss.
In later gear, say the 50s, the "good" rate is much improved but certain
types like the banded black beauties are notoriously bad as are those
pink plastic ones found in 50s/60s Hallicrafters gear.
The debate lingers on just how much performance degradation and
reliability can be tolerated since the bad caps may not have a
particular detrimental effect *today* depending on where in the circuit
they are used. I suppose it depends whether or not you are "restoring"
or "repairing".
I cross-posted this to rec.antiques.radio+phono so you could catch some
other opinions.
Good luck!
-Bill

On Sun, 19 Oct 2003 10:12:52 -0400, --exray-- wrote:

The digital voltmeters often have a capacitance test function but are
thrown off in the presence of leakage. Again, if it doesn't measure
right, out she goes.

I have both a dedicated Capacitor meter and a multimeter that measures
capacitance. Both do the same thing when presented with leaky caps.
The cap will invariably read two or three times more than what its
value is supposed to be.

I have tested brand new electrolytics and have found them to be as
much as 50% off rated capacity. Small coupling and bypass caps, though
are usually right on the money if they're good.

-Scott



To reply to this message via e-mail, replace "fromrarp" in the e-mail address with "scott"

On Sun, 19 Oct 2003 10:12:52 -0400, --exray-- wrote:

The digital voltmeters often have a capacitance test function but are
thrown off in the presence of leakage. Again, if it doesn't measure
right, out she goes.

I have both a dedicated Capacitor meter and a multimeter that measures
capacitance. Both do the same thing when presented with leaky caps.
The cap will invariably read two or three times more than what its
value is supposed to be.

I have tested brand new electrolytics and have found them to be as
much as 50% off rated capacity. Small coupling and bypass caps, though
are usually right on the money if they're good.

-Scott



To reply to this message via e-mail, replace "fromrarp" in the e-mail address with "scott"

I would take the approach that failing the ohmmeter test means definitely
bad, but even passing the ohmmeter test means nothing better than
"doubtful."

I used to try to analyze the importance of leakage in a particular part, and
try to "calculate " the leakage based on circuit voltages. For example, I'd
measure the grid voltage and from that try to guess whether the coupling cap
was too leaky. I also tried the ohmmeter thing.

I gave up. I have since used a Heath IT-28 capacitor tester, with excellent
results. The criteria it uses are that a good electrolytic leaks less than 2
mA, a "small" electrolytic less that 15 uA, and a paper-mica-polyester
etc.less than 2 uA AT THE RATED VOLTAGE. The ability to apply any more than
a very small voltage to the cap is the downfall of the ohmmeter methods.

I have tried digital capacitor testers but they have a hard time identifying
leakage, and often just read the wrong value of capacitance.

For testing boatanchor-era caps, I would strongly suggest that you get one
of the same-era capacitor bridges that let you test with real voltage
applied. I like the Heath, but I have also used the Sprague and I am sure
many others are just as good.

I went through my junk box and probably threw out 1/2 of what I thought were
good caps. As other posters have indicated the banded Black Beauties are ALL
bad, the ones with yellow lettering are ALMOST all bad, but surprisingly the
ones with pink lettering are still largely OK. Anything dipped in wax is
shot.

Anyway, my vote is for a good, old cap bridge. Now, if someone would just
invent an LED substitute for the 6E5s in these things.



"--exray--" wrote in message
...
gil wrote:
I always heard about leaky caps being a problem with boatanchors, other
than
checking for the capacitor value is there a way to check if its a "leaky
cap" using just a multitester or voltmeter?

Thanks.....gil


There's some good capacitor testers around but as a rule on older BAs
(30s-40s) if it doesn't pass an ohmmeter test you need not go any
further. I chuck anything over about 1 Meg of leakage which tends to be
most all wax/paper caps from that era.
The digital voltmeters often have a capacitance test function but are
thrown off in the presence of leakage. Again, if it doesn't measure
right, out she goes.
The problem is due to the breakdown of the paper dielectric inside. For
the most part thats inevitable in spite of how well sealed it is. Some
of the high-end mil-spec metal cased guys have survived but thats about
all. The rest are hit-and-miss.
In later gear, say the 50s, the "good" rate is much improved but certain
types like the banded black beauties are notoriously bad as are those
pink plastic ones found in 50s/60s Hallicrafters gear.
The debate lingers on just how much performance degradation and
reliability can be tolerated since the bad caps may not have a
particular detrimental effect *today* depending on where in the circuit
they are used. I suppose it depends whether or not you are "restoring"
or "repairing".
I cross-posted this to rec.antiques.radio+phono so you could catch some
other opinions.
Good luck!
-Bill

I would take the approach that failing the ohmmeter test means definitely
bad, but even passing the ohmmeter test means nothing better than
"doubtful."

I used to try to analyze the importance of leakage in a particular part, and
try to "calculate " the leakage based on circuit voltages. For example, I'd
measure the grid voltage and from that try to guess whether the coupling cap
was too leaky. I also tried the ohmmeter thing.

I gave up. I have since used a Heath IT-28 capacitor tester, with excellent
results. The criteria it uses are that a good electrolytic leaks less than 2
mA, a "small" electrolytic less that 15 uA, and a paper-mica-polyester
etc.less than 2 uA AT THE RATED VOLTAGE. The ability to apply any more than
a very small voltage to the cap is the downfall of the ohmmeter methods.

I have tried digital capacitor testers but they have a hard time identifying
leakage, and often just read the wrong value of capacitance.

For testing boatanchor-era caps, I would strongly suggest that you get one
of the same-era capacitor bridges that let you test with real voltage
applied. I like the Heath, but I have also used the Sprague and I am sure
many others are just as good.

I went through my junk box and probably threw out 1/2 of what I thought were
good caps. As other posters have indicated the banded Black Beauties are ALL
bad, the ones with yellow lettering are ALMOST all bad, but surprisingly the
ones with pink lettering are still largely OK. Anything dipped in wax is
shot.

Anyway, my vote is for a good, old cap bridge. Now, if someone would just
invent an LED substitute for the 6E5s in these things.



"--exray--" wrote in message
...
gil wrote:
I always heard about leaky caps being a problem with boatanchors, other
than
checking for the capacitor value is there a way to check if its a "leaky
cap" using just a multitester or voltmeter?

Thanks.....gil


There's some good capacitor testers around but as a rule on older BAs
(30s-40s) if it doesn't pass an ohmmeter test you need not go any
further. I chuck anything over about 1 Meg of leakage which tends to be
most all wax/paper caps from that era.
The digital voltmeters often have a capacitance test function but are
thrown off in the presence of leakage. Again, if it doesn't measure
right, out she goes.
The problem is due to the breakdown of the paper dielectric inside. For
the most part thats inevitable in spite of how well sealed it is. Some
of the high-end mil-spec metal cased guys have survived but thats about
all. The rest are hit-and-miss.
In later gear, say the 50s, the "good" rate is much improved but certain
types like the banded black beauties are notoriously bad as are those
pink plastic ones found in 50s/60s Hallicrafters gear.
The debate lingers on just how much performance degradation and
reliability can be tolerated since the bad caps may not have a
particular detrimental effect *today* depending on where in the circuit
they are used. I suppose it depends whether or not you are "restoring"
or "repairing".
I cross-posted this to rec.antiques.radio+phono so you could catch some
other opinions.
Good luck!
-Bill

I picked up a highly-regarded Sprague "Tel-Ohmike TO-4" R-C bridge,
and found that it was loaded with Sprague Black Beauty capacitors.

It's funny that I'll have to first re-cap the bridge before
I can use it to test capacitors.

73,
Ed K4PF

I picked up a highly-regarded Sprague "Tel-Ohmike TO-4" R-C bridge,
and found that it was loaded with Sprague Black Beauty capacitors.

It's funny that I'll have to first re-cap the bridge before
I can use it to test capacitors.

73,
Ed K4PF

"Scott W. Harvey" wrote in message
...

[snip]


I have tested brand new electrolytics and have found them to be as
much as 50% off rated capacity. Small coupling and bypass caps, though
are usually right on the money if they're good.

-Scott



That's interesting. I've checked some new electrolytics with my old
Heathkit cap checker, and they are almost always within 20% or so of the
indicated value. I'll check more later and see if it still holds true.

Frank Dresser

"Scott W. Harvey" wrote in message
...

[snip]


I have tested brand new electrolytics and have found them to be as
much as 50% off rated capacity. Small coupling and bypass caps, though
are usually right on the money if they're good.

-Scott



That's interesting. I've checked some new electrolytics with my old
Heathkit cap checker, and they are almost always within 20% or so of the
indicated value. I'll check more later and see if it still holds true.

Frank Dresser

A tolerance of +100% -50% was more or less standard on old electrolytic
caps. Today, +50% -10% is customary, but some are still wider than that.

"Frank Dresser" wrote in message
...

"Scott W. Harvey" wrote in message
...

[snip]


I have tested brand new electrolytics and have found them to be as
much as 50% off rated capacity. Small coupling and bypass caps, though
are usually right on the money if they're good.

-Scott



That's interesting. I've checked some new electrolytics with my old
Heathkit cap checker, and they are almost always within 20% or so of the
indicated value. I'll check more later and see if it still holds true.

Frank Dresser

A tolerance of +100% -50% was more or less standard on old electrolytic
caps. Today, +50% -10% is customary, but some are still wider than that.

"Frank Dresser" wrote in message
...

"Scott W. Harvey" wrote in message
...

[snip]


I have tested brand new electrolytics and have found them to be as
much as 50% off rated capacity. Small coupling and bypass caps, though
are usually right on the money if they're good.

-Scott



That's interesting. I've checked some new electrolytics with my old
Heathkit cap checker, and they are almost always within 20% or so of the
indicated value. I'll check more later and see if it still holds true.

Frank Dresser

Frank Dresser wrote:
"Scott W. Harvey" wrote in message


I have tested brand new electrolytics and have found them to be as
much as 50% off rated capacity. Small coupling and bypass caps, though
are usually right on the money if they're good.

That's interesting. I've checked some new electrolytics with my old
Heathkit cap checker, and they are almost always within 20% or so of the
indicated value. I'll check more later and see if it still holds true.

Electrolytics are usually rated for -10%, +50% tolerances, and most of
them will measure higher than the package says. Check the data sheet
on the caps.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Frank Dresser wrote:
"Scott W. Harvey" wrote in message


I have tested brand new electrolytics and have found them to be as
much as 50% off rated capacity. Small coupling and bypass caps, though
are usually right on the money if they're good.

That's interesting. I've checked some new electrolytics with my old
Heathkit cap checker, and they are almost always within 20% or so of the
indicated value. I'll check more later and see if it still holds true.

Electrolytics are usually rated for -10%, +50% tolerances, and most of
them will measure higher than the package says. Check the data sheet
on the caps.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article , "BFoelsch"
writes:

For testing boatanchor-era caps, I would strongly suggest that you get one
of the same-era capacitor bridges that let you test with real voltage
applied. I like the Heath, but I have also used the Sprague and I am sure
many others are just as good.

I use the venerable Eico 950A bridge and leakage tester. You can dial up any
voltage up to around 500 and observe leakage on the magic eye tube; for
'lytics, a neon bulb in series is subbed for the eye tube. Once you charge the
cap up to rated voltage, the eye or bulb should show nothing.

Great for reforming lytics too. And the bridge is pretty accurate for
measurements.

But still, before cutting one end loose to check it, I find it worthwhile to
check grid and screen voltages in a radio to see if a cap is really leaking
enough to throw things off. --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

In article , "BFoelsch"
writes:

For testing boatanchor-era caps, I would strongly suggest that you get one
of the same-era capacitor bridges that let you test with real voltage
applied. I like the Heath, but I have also used the Sprague and I am sure
many others are just as good.

I use the venerable Eico 950A bridge and leakage tester. You can dial up any
voltage up to around 500 and observe leakage on the magic eye tube; for
'lytics, a neon bulb in series is subbed for the eye tube. Once you charge the
cap up to rated voltage, the eye or bulb should show nothing.

Great for reforming lytics too. And the bridge is pretty accurate for
measurements.

But still, before cutting one end loose to check it, I find it worthwhile to
check grid and screen voltages in a radio to see if a cap is really leaking
enough to throw things off. --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

BFoelsch wrote:
A tolerance of +100% -50% was more or less standard on old electrolytic
caps. Today, +50% -10% is customary, but some are still wider than that.

You've got to look long and hard to find any with that loose a spec
anymore. I just paged thru the Mouser catalog and a quick glance sez
everything offered is +/-20% except for the old Vishay/Sprague TVA-Atoms
and Littl-Lytics.

-Bill

BFoelsch wrote:
A tolerance of +100% -50% was more or less standard on old electrolytic
caps. Today, +50% -10% is customary, but some are still wider than that.

You've got to look long and hard to find any with that loose a spec
anymore. I just paged thru the Mouser catalog and a quick glance sez
everything offered is +/-20% except for the old Vishay/Sprague TVA-Atoms
and Littl-Lytics.

-Bill

"Frank Dresser" wrote in message
...


Here's the results, checked on a Heathkit IT-28:

BC HP 68ufd 200V
68-62-60

BC HP 47ufd 200V
43-44-46-44-44-43-45-45

BC HP 33ufd 200V
33-30-29-31-31-30-33-32

Xicon 47ufd 160V(Marked +/- 20%)
44-43-43-46-43-44-48

Xicon 33ufd 160V(Marked +/- 20%)
32-34-34-34-34-32-33-32

Panasonic 47ufd 450V
45-46-43

Ducati 100ufd 25V (about 30 years old)
98-100-100-98-105-95-105-102-110-100-110

Planet Liticap 40ufd 450V (used pull, maybe 40 years old)
38

Frank Dresser

"Frank Dresser" wrote in message
...


Here's the results, checked on a Heathkit IT-28:

BC HP 68ufd 200V
68-62-60

BC HP 47ufd 200V
43-44-46-44-44-43-45-45

BC HP 33ufd 200V
33-30-29-31-31-30-33-32

Xicon 47ufd 160V(Marked +/- 20%)
44-43-43-46-43-44-48

Xicon 33ufd 160V(Marked +/- 20%)
32-34-34-34-34-32-33-32

Panasonic 47ufd 450V
45-46-43

Ducati 100ufd 25V (about 30 years old)
98-100-100-98-105-95-105-102-110-100-110

Planet Liticap 40ufd 450V (used pull, maybe 40 years old)
38

Frank Dresser

For a radio that I intend to use regularly, I follow the credo, "kill 'em
all, let God sort them out." Why would you take a chance that a decades-old
electrolytic will survive for another hour, day, or week? You can replace it
as fast as you can test it, and if you guess wrong, it may cost you an
expensive power transformer. For the price of a few lattes or a couple of
beers, you can afford to put new electrolytics in your boatanchor and sleep
soundly :-)

If you want everything to look original, you can stuff new capacitors inside
the old containers. See the article at http://antiqueradio.org/recap.htm .

Happy listening.

Phil Nelson
http://antiqueradio.org/index.html

For a radio that I intend to use regularly, I follow the credo, "kill 'em
all, let God sort them out." Why would you take a chance that a decades-old
electrolytic will survive for another hour, day, or week? You can replace it
as fast as you can test it, and if you guess wrong, it may cost you an
expensive power transformer. For the price of a few lattes or a couple of
beers, you can afford to put new electrolytics in your boatanchor and sleep
soundly :-)

If you want everything to look original, you can stuff new capacitors inside
the old containers. See the article at http://antiqueradio.org/recap.htm .

Happy listening.

Phil Nelson
http://antiqueradio.org/index.html

In article , "Frank
Dresser" writes:

Here's the results, checked on a Heathkit IT-28:

Interesting. With very few and small exceptions, every cap measured LESS than
marked. And we thought lytics were being made with very high positive
tolerances, up to 100% or double the value.

I guess you get (almost) what you pay for, no mas! --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

In article , "Frank
Dresser" writes:

Here's the results, checked on a Heathkit IT-28:

Interesting. With very few and small exceptions, every cap measured LESS than
marked. And we thought lytics were being made with very high positive
tolerances, up to 100% or double the value.

I guess you get (almost) what you pay for, no mas! --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

In article . net, "Phil
Nelson" writes:

For a radio that I intend to use regularly, I follow the credo, "kill 'em
all, let God sort them out." Why would you take a chance that a decades-old
electrolytic will survive for another hour, day, or week? You can replace it
as fast as you can test it, and if you guess wrong, it may cost you an
expensive power transformer.

Amen. I had a lovely old Philco mini-console literally blow up (clouds of
steam nad smoke) while playing away as I worked on something else. Haven't
checked yet to see if the power trans went, but there's black goo all over the
chassis -- want to give it a year to dry out of any toxic stuff.

Then there was the night I left an antique lytic re-forming overnight on my
favorite laboratory variable power supply. It was doing great. Next AM, I
find the cap is still looking great, but the power supply's insides are a
charred mass of clinkers. Enough soot on the ceiling joists to make be
thankful I still had a house to live in.

For the price of a few lattes or a couple of
beers, you can afford to put new electrolytics in your boatanchor and sleep
soundly :-)

Actually, that's more like a couple lattes or a 6-pack of beer, but the point
is well taken! --Mike K.



Oscar loves trash, but hates Spam! Delete him to reply to me.

In article . net, "Phil
Nelson" writes:

For a radio that I intend to use regularly, I follow the credo, "kill 'em
all, let God sort them out." Why would you take a chance that a decades-old
electrolytic will survive for another hour, day, or week? You can replace it
as fast as you can test it, and if you guess wrong, it may cost you an
expensive power transformer.

Amen. I had a lovely old Philco mini-console literally blow up (clouds of
steam nad smoke) while playing away as I worked on something else. Haven't
checked yet to see if the power trans went, but there's black goo all over the
chassis -- want to give it a year to dry out of any toxic stuff.

Then there was the night I left an antique lytic re-forming overnight on my
favorite laboratory variable power supply. It was doing great. Next AM, I
find the cap is still looking great, but the power supply's insides are a
charred mass of clinkers. Enough soot on the ceiling joists to make be
thankful I still had a house to live in.

For the price of a few lattes or a couple of
beers, you can afford to put new electrolytics in your boatanchor and sleep
soundly :-)

Actually, that's more like a couple lattes or a 6-pack of beer, but the point
is well taken! --Mike K.



Oscar loves trash, but hates Spam! Delete him to reply to me.

"Mike Knudsen" wrote in message
...


Interesting. With very few and small exceptions, every cap measured LESS
than
marked. And we thought lytics were being made with very high positive
tolerances, up to 100% or double the value.

I guess you get (almost) what you pay for, no mas! --Mike K.


I can't be sure the checker isn't just reading low. I do get repeatable and
sensible readings from it.

I also don't know if the caps I checked just by chance happened to be
generally bunched around common values, or if they are actually made with
more precision than they are rated for. It's a small sample.

But modern (maybe even 50 years ago) manufacturing ought to be able to make
a reasonably precise product as long as they are able to stick with a
process that is known to work. I have to figure that the capacitor
manufacturers know what they are doing, they regularly check samples of
their product and can make running changes to hit their target specs with
almost every lot.

Just as speculation, let's say cap manufacturers have learned to make
electrolytic capacitors with good precision at little extra cost. And let's
imagine that setting the target capacitance to 5% - 10% low reduces the cost
of the "active ingredients" by 5% -10%. Well, that would be a nice reward
for knowing how to do the job!

Frank Dresser

"Mike Knudsen" wrote in message
...


Interesting. With very few and small exceptions, every cap measured LESS
than
marked. And we thought lytics were being made with very high positive
tolerances, up to 100% or double the value.

I guess you get (almost) what you pay for, no mas! --Mike K.


I can't be sure the checker isn't just reading low. I do get repeatable and
sensible readings from it.

I also don't know if the caps I checked just by chance happened to be
generally bunched around common values, or if they are actually made with
more precision than they are rated for. It's a small sample.

But modern (maybe even 50 years ago) manufacturing ought to be able to make
a reasonably precise product as long as they are able to stick with a
process that is known to work. I have to figure that the capacitor
manufacturers know what they are doing, they regularly check samples of
their product and can make running changes to hit their target specs with
almost every lot.

Just as speculation, let's say cap manufacturers have learned to make
electrolytic capacitors with good precision at little extra cost. And let's
imagine that setting the target capacitance to 5% - 10% low reduces the cost
of the "active ingredients" by 5% -10%. Well, that would be a nice reward
for knowing how to do the job!

Frank Dresser

I thought I might continue to save my old caps because some restorer
might want the 'original waxed paper' to stuff a new cap into.
Do I need to take more meds?

I thought I might continue to save my old caps because some restorer
might want the 'original waxed paper' to stuff a new cap into.
Do I need to take more meds?

In article , "Frank
Dresser" writes:

Just as speculation, let's say cap manufacturers have learned to make
electrolytic capacitors with good precision at little extra cost. And let's
imagine that setting the target capacitance to 5% - 10% low reduces the cost
of the "active ingredients" by 5% -10%. Well, that would be a nice reward
for knowing how to do the job!

This makes very good sense.
I suspect that back in the old days, manufacturers would throw in up to 100%
extra foil plates area just to make sure they at least met the rated
capacitance. So you would get caps well over the ratings.

But yes, once they got the process down really tight, why toss in extra
material. In fact, shaving it on the low side is just what the front-office
bean coutners probably tell them to do nowadays! --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

In article , "Frank
Dresser" writes:

Just as speculation, let's say cap manufacturers have learned to make
electrolytic capacitors with good precision at little extra cost. And let's
imagine that setting the target capacitance to 5% - 10% low reduces the cost
of the "active ingredients" by 5% -10%. Well, that would be a nice reward
for knowing how to do the job!

This makes very good sense.
I suspect that back in the old days, manufacturers would throw in up to 100%
extra foil plates area just to make sure they at least met the rated
capacitance. So you would get caps well over the ratings.

But yes, once they got the process down really tight, why toss in extra
material. In fact, shaving it on the low side is just what the front-office
bean coutners probably tell them to do nowadays! --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

"Mike Knudsen" wrote in message
...

This makes very good sense.
I suspect that back in the old days, manufacturers would
throw in up to 100%
extra foil plates area just to make sure they at least met
the rated
capacitance. So you would get caps well over the ratings.

But yes, once they got the process down really tight, why
toss in extra
material. In fact, shaving it on the low side is just
what the front-office
bean coutners probably tell them to do nowadays! --Mike
K.

Oscar loves trash, but hates Spam! Delete him to reply to
me.

I don't think I've ever seen an electrolytic capacitor read
more than 20% high, and even that range is very rare. Even
on the few low ESR survivors from the late 40's - early
50's. I'm not using a lab quality bridge, or checking large
numbers of electrolytic capacitors, so I can't come to
really firm conclusions. But I'm thinking the manufacturing
process was reasonably precise by 1950.

I don't know if the comparision holds, but carbon
composition resistors were getting more precise all through
that era, as well. The 5%ers were pretty common around
1970. I have to wonder how much expense was added to the
more precise resistors just for keeping extra inventory.
There's about twice as many values for 10%ers as 20%ers.
Double it again for the 5%ers. Assuming the cap makers
could reliably come with 5% electrolytics, would there be
any value to stocking 4 times as many values? I can't think
of any. They are used almost entirely for power supply
filtering, or audio coupling. So maybe they kept the old
20% spec on 5% tolerence caps only to keep inventory simple.

Frank Dresser

"Mike Knudsen" wrote in message
...

This makes very good sense.
I suspect that back in the old days, manufacturers would
throw in up to 100%
extra foil plates area just to make sure they at least met
the rated
capacitance. So you would get caps well over the ratings.

But yes, once they got the process down really tight, why
toss in extra
material. In fact, shaving it on the low side is just
what the front-office
bean coutners probably tell them to do nowadays! --Mike
K.

Oscar loves trash, but hates Spam! Delete him to reply to
me.

I don't think I've ever seen an electrolytic capacitor read
more than 20% high, and even that range is very rare. Even
on the few low ESR survivors from the late 40's - early
50's. I'm not using a lab quality bridge, or checking large
numbers of electrolytic capacitors, so I can't come to
really firm conclusions. But I'm thinking the manufacturing
process was reasonably precise by 1950.

I don't know if the comparision holds, but carbon
composition resistors were getting more precise all through
that era, as well. The 5%ers were pretty common around
1970. I have to wonder how much expense was added to the
more precise resistors just for keeping extra inventory.
There's about twice as many values for 10%ers as 20%ers.
Double it again for the 5%ers. Assuming the cap makers
could reliably come with 5% electrolytics, would there be
any value to stocking 4 times as many values? I can't think
of any. They are used almost entirely for power supply
filtering, or audio coupling. So maybe they kept the old
20% spec on 5% tolerence caps only to keep inventory simple.

Frank Dresser

In article , "Williams"
writes:

I thought I might continue to save my old caps because some restorer
might want the 'original waxed paper' to stuff a new cap into.
Do I need to take more meds?

Nope, you make sense. Maybe not so much demand in the Ham BA world, but over
on radio+phono you'll find purists who want caps to stuff. The problem is,
they already have the original old caps in the radio they're restoring, so they
don't need yours.

But -- some enterprising retiree may want to stockpile pre-stuffed restored
caps and sell them to other restorers, ready for insertion in the radio. If
so, he'd want yours for starters to build up inventory. Ultimately, he'd take
the old ones in exchange, but meanwhile he needs extras.

Hopefully he'd pay enough to cover the postage :-) --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

In article , "Williams"
writes:

I thought I might continue to save my old caps because some restorer
might want the 'original waxed paper' to stuff a new cap into.
Do I need to take more meds?

Nope, you make sense. Maybe not so much demand in the Ham BA world, but over
on radio+phono you'll find purists who want caps to stuff. The problem is,
they already have the original old caps in the radio they're restoring, so they
don't need yours.

But -- some enterprising retiree may want to stockpile pre-stuffed restored
caps and sell them to other restorers, ready for insertion in the radio. If
so, he'd want yours for starters to build up inventory. Ultimately, he'd take
the old ones in exchange, but meanwhile he needs extras.

Hopefully he'd pay enough to cover the postage :-) --Mike K.

Oscar loves trash, but hates Spam! Delete him to reply to me.

Williams wrote:
I thought I might continue to save my old caps because some restorer
might want the 'original waxed paper' to stuff a new cap into.
Do I need to take more meds?



Send 'em this a way, Jimmy. Ken G just blessed me with some but I can
always use more!
-Bill M
exray at caribe.net

Williams wrote:
I thought I might continue to save my old caps because some restorer
might want the 'original waxed paper' to stuff a new cap into.
Do I need to take more meds?



Send 'em this a way, Jimmy. Ken G just blessed me with some but I can
always use more!
-Bill M
exray at caribe.net

Mike Knudsen wrote:

Nope, you make sense. Maybe not so much demand in the Ham BA world, but over
on radio+phono you'll find purists who want caps to stuff. The problem is,
they already have the original old caps in the radio they're restoring, so they
don't need yours.

Not always...thats why I need more. Often times the original caps have
already been hacked out or are in too terrible a condition for restuffing.
I try to keep some made up ahead of time and where a set like a Zenith
or Philco uses brand specific ones I like to replace with the same. I
considered stuff-n-sell but it really is a time consuming task. I'd
feel stupid trying to sell them at what they are worth dollar-wise in
time...and of course anyone can do their own for free if they really care!

But -- some enterprising retiree may want to stockpile pre-stuffed restored
caps and sell them to other restorers, ready for insertion in the radio. If
so, he'd want yours for starters to build up inventory. Ultimately, he'd take
the old ones in exchange, but meanwhile he needs extras.

Hopefully he'd pay enough to cover the postage :-) --Mike K.

I beg for these things! And of course always pay postage!

-Bill