Paper capacitor recap opinions?
 

"Keep a cheap set of imported clip leads handy. Place a set over the snipped
leads to "remind" where the old part was snipped from."

Great Idea. Why didn't I think of that. Now I will be able to keep
repairing radios clear into senility.

Thanks, Colin K7FM

Paper capacitor recap opinions?
 

On Oct 17, 7:38 pm, "COLIN LAMB" wrote:
And, Phil's website is as good and concise as it gets about replacing
capacitors. Seehttp://antiqueradio.org/recap.htm

Even if you have been doing it for years, you will appreciate Phil's nice
writing style and useful information.

And, a big fat A for taking the time to help spread his wisdom, learned from
years of experience.

Even after years of repairing radios, we learn that we can do it better. A
few years ago I was going to replace a paper cap in a 17 tube receiver. I
do them one at a time. I clipped the old one out, got a phone call and
dinner call and shut the soldering iron off and left. I was not able to
return to the work for about a month. By then, I knew there was a capacitor
out - but I had clipped the old leads off and it took me an hour of tracing
and schematic reading before I could determine where the missing capacitor
was. Now, I am more methodical and make notes before I clip the capacitor.
A notebook and pencil are always nearby to document before I start work.
Life has been much simpler since then. And, it really is a good idea to
test the radio after a maximum number of changes.

Colin K7FM

Colin has it right. I had a similar experience. Ever since, I keep a
digital camera close and take close-up pictures as the work
progresses. I can always check my work, and I have a set of pictures
afterwards to show off.
I also keep a scratch copy of the radio manual's component list and
schematic that I mark up during the job. When I hand the radio over to
the owner, I can show him exactly what I did to restore the radio.
Gary WA7MLK

Paper capacitor recap opinions?
 

"COLIN LAMB" wrote in message
...
And, Phil's website is as good and concise as it gets
about replacing capacitors. See
http://antiqueradio.org/recap.htm

Even if you have been doing it for years, you will
appreciate Phil's nice writing style and useful
information.

And, a big fat A for taking the time to help spread his
wisdom, learned from years of experience.

Even after years of repairing radios, we learn that we can
do it better. A few years ago I was going to replace a
paper cap in a 17 tube receiver. I do them one at a time.
I clipped the old one out, got a phone call and dinner
call and shut the soldering iron off and left. I was not
able to return to the work for about a month. By then, I
knew there was a capacitor out - but I had clipped the old
leads off and it took me an hour of tracing and schematic
reading before I could determine where the missing
capacitor was. Now, I am more methodical and make notes
before I clip the capacitor. A notebook and pencil are
always nearby to document before I start work. Life has
been much simpler since then. And, it really is a good
idea to test the radio after a maximum number of changes.

Colin K7FM
I will add to what is on this page that the flat molded
caps are often also mica types, however, they are not
silvered micas. They are simply stacks of alternating mica
dielectric and foil plates. They are not as reliable or high
performance as silvered micas and should be checked. These
were used mostly in high voltage applications or where waxed
paper had too much loss.
Black Beauty caps are not exactly paper dielectric but
used paper impregnated with a polyester. They _should_ have
been low loss and quite reliable but became notorious within
a few years of their manufacture for developing high losses.
I suspect this may have been due to some problem with the
molded casing because Sprague sold capacotors with a similar
construction but in dipped epoxy casing as Orange Drops and
I have not heard that they shared the same short life
problems.
BTW, while silvered mica caps are generally very
reliable they can still go bad. I've had to replace quite a
few in rebuilding a couple of SP-600-JX's due to
instability. Here again all were molded bakelite cases so I
suspect either the case or perhaps end connections. Again,
the dipped epoxy mica caps do not seem to suffer from this
problem.


--
---
Richard Knoppow
Los Angeles, CA, USA

Paper capacitor recap opinions?
 

Yes, the flat molded micas are starting to show their age. Although
generally more reliable than paper, I have found some bad ones in recent
1940s TV projects.

When in doubt, check 'em!

I read somewhere else that the plastic casing in Black Beauties, etc.,
developed microscopic cracks and admitted water vapor over the years,
causing the same problems as in paper caps.

Phil Nelson

Paper capacitor recap opinions?
 

"Phil Nelson" wrote in message
...
Yes, the flat molded micas are starting to show their age.
Although generally more reliable than paper, I have found
some bad ones in recent 1940s TV projects.

When in doubt, check 'em!

I read somewhere else that the plastic casing in Black
Beauties, etc., developed microscopic cracks and admitted
water vapor over the years, causing the same problems as
in paper caps.

Phil Nelson
That may be, they certainly develop very large cracks
sometimes. I've disected a few BBs. The capacitor itself was
distorted, oddly flattened rather than being tubular.
Perhaps they were wound this way or perhaps some sort of
differential shrinkage of the encapsulation pushed them out
of shape. They were _supposed_ to be very long life, low
leakage, deluxe capacitors and are generally found in high
quality equipment.


--
---
Richard Knoppow
Los Angeles, CA, USA

Paper capacitor recap opinions?
 

I think the designers were using the best materials & technology available
at the time. And they never imagined that people might be using or restoring
these devices several decades beyond their expected service life. Most
radios were considered appliances. Contemporary electronics, even cars for
that matter, are not designed to remain in use forever. I remember when my
Dad bought a Mercury in 1965, his one and only new car. What would the
salesman have said if Dad had asked how that car might be running some
40-odd years later? Dad is still alive, bless his heart, but the car
perished decades ago.

:-)

Phil Nelson

"Richard Knoppow" wrote in message
...
That may be, they certainly develop very large cracks sometimes. I've
disected a few BBs. The capacitor itself was distorted, oddly flattened
rather than being tubular. Perhaps they were wound this way or perhaps
some sort of differential shrinkage of the encapsulation pushed them out
of shape. They were _supposed_ to be very long life, low leakage, deluxe
capacitors and are generally found in high quality equipment.

Paper capacitor recap opinions?
 

"Phil Nelson" wrote in message
...
I think the designers were using the best materials &
technology available at the time. And they never imagined
that people might be using or restoring these devices
several decades beyond their expected service life. Most
radios were considered appliances. Contemporary
electronics, even cars for that matter, are not designed to
remain in use forever. I remember when my Dad bought a
Mercury in 1965, his one and only new car. What would the
salesman have said if Dad had asked how that car might be
running some 40-odd years later? Dad is still alive, bless
his heart, but the car perished decades ago.

:-)

Phil Nelson

My memory is that the problems with the BBs began
showing up pretty soon after manufacture. For instance,
Hammarlund used them in SP-600 receivers made in the mid
1950's but the military was replacing them in mass with disc
ceramics by the late 1950's, so something must have changed
pretty rapidly. However, they were still being advertised in
the early 1960's so, perhaps, the problem was cured and it
was only the early versions that were bad.


--
---
Richard Knoppow
Los Angeles, CA, USA

Paper capacitor recap opinions?
 

Phil Nelson wrote:
I think the designers were using the best materials & technology
available at the time. And they never imagined that people might be
using or restoring these devices several decades beyond their expected
service life. Most radios were considered appliances. Contemporary
electronics, even cars for that matter, are not designed to remain in
use forever. I remember when my Dad bought a Mercury in 1965, his one
and only new car. What would the salesman have said if Dad had asked how
that car might be running some 40-odd years later? Dad is still alive,
bless his heart, but the car perished decades ago.

My Mom still drives a '68 Rambler, and my Dad drove a '65 Dodge Dart
up until he died a couple of years ago. The car is still on the road.

-Chuck

Paper capacitor recap opinions?
 

Now, I am more methodical and make notes before I clip the capacitor.
A notebook and pencil are always nearby to document before I start work.
Life has been much simpler since then. And, it really is a good idea to
test the radio after a maximum number of changes.

Colin K7FM

Use an alligator jumper to mark the connection point of the old cap. This
has saved me numerous times.

Paul P.

www.ppinyot.com

Paper capacitor recap opinions?
 

"Richard Knoppow" wrote in message
...

"COLIN LAMB" wrote in message
...
And, Phil's website is as good and concise as it gets about replacing
capacitors. See http://antiqueradio.org/recap.htm

Even if you have been doing it for years, you will appreciate Phil's nice
writing style and useful information.

And, a big fat A for taking the time to help spread his wisdom, learned
from years of experience.

Even after years of repairing radios, we learn that we can do it better.
A few years ago I was going to replace a paper cap in a 17 tube receiver.
I do them one at a time. I clipped the old one out, got a phone call and
dinner call and shut the soldering iron off and left. I was not able to
return to the work for about a month. By then, I knew there was a
capacitor out - but I had clipped the old leads off and it took me an
hour of tracing and schematic reading before I could determine where the
missing capacitor was. Now, I am more methodical and make notes before I
clip the capacitor. A notebook and pencil are always nearby to document
before I start work. Life has been much simpler since then. And, it
really is a good idea to test the radio after a maximum number of
changes.

Colin K7FM
I will add to what is on this page that the flat molded caps are often
also mica types, however, they are not silvered micas. They are simply
stacks of alternating mica dielectric and foil plates. They are not as
reliable or high performance as silvered micas and should be checked.
These were used mostly in high voltage applications or where waxed paper
had too much loss.
Black Beauty caps are not exactly paper dielectric but used paper
impregnated with a polyester. They _should_ have been low loss and quite
reliable but became notorious within a few years of their manufacture for
developing high losses. I suspect this may have been due to some problem
with the molded casing because Sprague sold capacotors with a similar
construction but in dipped epoxy casing as Orange Drops and I have not
heard that they shared the same short life problems.
BTW, while silvered mica caps are generally very reliable they can
still go bad. I've had to replace quite a few in rebuilding a couple of
SP-600-JX's due to instability. Here again all were molded bakelite cases
so I suspect either the case or perhaps end connections. Again, the dipped
epoxy mica caps do not seem to suffer from this problem.


--
---
Richard Knoppow
Los Angeles, CA, USA



I discovered that any of the flat "Domino" style caps with Micamold stamped
on them are best replaced.

Paul P.