Paper capacitor recap opinions?
 

I am in the process of recapping one of my receivers that uses many 0.05 MFD
paper caps. Since 0.05s are not READILY available, I am split equally on the
following:

1. Do I recap using the more readily available 0.047
MFD caps even though they are of less capacity
than the original? OR...

2. Do I recap by paralleling readily available
0.022 and 0.033 for a total capacity of
0.055 MFD?

If I do the 0.047 replacement I am violating the
rule I have had beaten in to me about NEVER allow a capacitor to be of LESS
capacity...but when they are
higher it is OK. However 0.047 MF is only 0.003 MFD
off the target 0.05 MFD value whereas the "safer" higher parallel
combination (0.055 MFD) is 0.005 MFD higher than the target capacity.

Thoughts? My receiver uses a lot of the 0.05s so it is not like I only
have one or two to consider.

Thanks for any help.

Gary

Paper capacitor recap opinions?
 

"SX-88" wrote in message
...
I am in the process of recapping one of my receivers that uses many 0.05
MFD
paper caps. Since 0.05s are not READILY available, I am split equally on
the
following:

1. Do I recap using the more readily available 0.047
MFD caps even though they are of less capacity
than the original? OR...

2. Do I recap by paralleling readily available
0.022 and 0.033 for a total capacity of
0.055 MFD?

If I do the 0.047 replacement I am violating the
rule I have had beaten in to me about NEVER allow a capacitor to be of
LESS
capacity...but when they are
higher it is OK. However 0.047 MF is only 0.003 MFD
off the target 0.05 MFD value whereas the "safer" higher parallel
combination (0.055 MFD) is 0.005 MFD higher than the target capacity.

Thoughts? My receiver uses a lot of the 0.05s so it is not like I
only
have one or two to consider.

Thanks for any help.

Gary

Gary,
Personal opinion here... I wouldn't hesitate for a heartbeat
to put in the .047s. They're well within the manufacturer's margin
of error in any case. And single .047s are much cheaper and
better looking than a bunch of paralleled caps.
Also... personal opinion as well, I've intentionally used much
smaller caps than OEM in some circuit locations, such as line
bypasses.
Cheers,
Nelson

Paper capacitor recap opinions?
 

SX-88 wrote:
I am in the process of recapping one of my receivers that uses many 0.05 MFD
paper caps. Since 0.05s are not READILY available, I am split equally on the
following:

1. Do I recap using the more readily available 0.047
MFD caps even though they are of less capacity
than the original? OR...



I agree... There is absolutely no reason not to use .047's.
de K3HVG

Paper capacitor recap opinions?
 

I third the motion. You can actually calculate the needed capacity in any
particular circuit, whether it be bypassing or coupling. The chance that
any particular .05ufd capacitor originally used by the reeceiver
manufacturer would be the calculated value is about as as slim as finding a
nice SX-88 at a landfill. Ballpark is close enough, unless it is in a tuned
circuit.

And, the capacitors usually have a tolerance far greater than the .03 ufd
difference.

Use the .047 and do not give it another thought.

73, Colin K7FM

Paper capacitor recap opinions?
 

"SX-88" wrote in message
...
I am in the process of recapping one of my receivers that uses many 0.05
MFD
paper caps. Since 0.05s are not READILY available, I am split equally on
the
following:

Thanks for any help.

Gary


3000 pF isn't going to make much difference in a .05 mFd bypass. You can get
the .05
values from NTE if you feel the need to keep it original. JustRadios.com
probably
has them too. Personally, I'd use the best quality axial lead yellow
jackets I could find.
If you really want to keep it original, consider
restuffing the old cardboard shells from the wax caps to preserve the under
chassis
appearance.

Pete

Paper capacitor recap opinions?
 

COLIN LAMB wrote:
I third the motion. You can actually calculate the needed capacity in any
particular circuit, whether it be bypassing or coupling. The chance that
any particular .05ufd capacitor originally used by the reeceiver
manufacturer would be the calculated value is about as as slim as finding a
nice SX-88 at a landfill. Ballpark is close enough, unless it is in a tuned
circuit.

Note that some of these WILL be in tuned circuits, and you'll almost certainly
need to realign the receiver with a sweep generator afterward. But that is
not a bad thing.

And, the capacitors usually have a tolerance far greater than the .03 ufd
difference.

Yes, figure 20% tolerances on those things.

Use the .047 and do not give it another thought.

If you really worry, you can get .05 uF orange drops.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Paper capacitor recap opinions?
 

On Oct 16, 11:41 am, "SX-88" wrote:
I am in the process of recapping one of my receivers that uses many 0.05 MFD
paper caps. Since 0.05s are not READILY available, I am split equally on the
following:

1. Do I recap using the more readily available 0.047
MFD caps even though they are of less capacity
than the original? OR...

2. Do I recap by paralleling readily available
0.022 and 0.033 for a total capacity of
0.055 MFD?

If I do the 0.047 replacement I am violating the
rule I have had beaten in to me about NEVER allow a capacitor to be of LESS
capacity...but when they are
higher it is OK. However 0.047 MF is only 0.003 MFD
off the target 0.05 MFD value whereas the "safer" higher parallel
combination (0.055 MFD) is 0.005 MFD higher than the target capacity.

Thoughts? My receiver uses a lot of the 0.05s so it is not like I only
have one or two to consider.

Thanks for any help.

Gary


One more thought Gary,
You can look at the application and determine what the purpose of the
capacitor is, the approximate frequency, and the Xc of the capacitor
at that frequency. For instance, it it is in the IF amplifier stage,
you know that the frequency is 455KHz, and can calculate Xc. From
that, you can determine what range of values makes sense to replace
into the radio.
That said, remember that those paper capacitors had values given at
+/-20% tolerance. So why do you have a rule beat into you that you
never replace a capacitor with a value less than the original?
I just re-capped a Hallicrafters S-53A. The paper capacitors are ALL
rated at 600V. However, many of them are in low voltage applications,
and never see more that 30 volts accross them. Why put in a HUGE paper
capacitor? Because it was cheaper for the company to stock just one
part type and use it wherever a .01uF capacitor was needed.
So it is OK to question why a given component is where it is, and make
a judgement call on what would be a good replacement.
Also, as I replace the paper capacitors, I like to wear gloves. The
wax is kind of nasty to get on you.
Have fun, and good luck,
Gary

Paper capacitor recap opinions?
 

about as as slim as finding a nice SX-88 at a landfill.

Hey, whaddya mean?!?

http://www.antiqueradio.org/dumpster.htm

:-)

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/html

P.S. I agree with other responders that the .047 is a fine replacement.
Since the old caps were manufactured to such a wide tolerance, your modern
replacements may be closer to the specified value than most of the
originals!

Paper capacitor recap opinions?
 

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

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
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


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.

Digital photos of sections of the under chassis are also great visual
reminders.

Pete k1zjh

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.

Paper capacitor recap opinions?
 

Paul P REMOVE paul @ REMOVE ppinyot . REMOVEcom wrote:

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

Sheesh, and we still have boxes of the things brand new at work...
-s-cott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Paper capacitor recap opinions?
 

"Scott Dorsey" wrote in message
...
Paul P REMOVE paul @ REMOVE ppinyot . REMOVEcom wrote:

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

Sheesh, and we still have boxes of the things brand new at
work...
-s-cott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I would test them before use. These are mostly stacks of
mica dielectric and aluminum foil electrodes rather than
plated "silver mica" types. Mostly, they were use for high
voltage transmitter circuits. They do not have the stability
and very low leakage of the plated type but were useful for
HV bypass use. I think they may suffer from the same
problems with degradation of the bakelite shell that other
caps seem to have. Also, the fact is that most of these caps
are getting to be very old.


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

Paper capacitor recap opinions?
 

"Richard Knoppow" wrote in message
...

"Scott Dorsey" wrote in message
...
Paul P REMOVE paul @ REMOVE ppinyot . REMOVEcom wrote:

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

Sheesh, and we still have boxes of the things brand new at
work...
-s-cott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I would test them before use.

[snip]

Testing actual old mica caps before use is good advice, but there's no need
to test anything above .001uf branded "Micamold". The notorious Micamold
was a paper cap in a mica type domino case. The values typically run in the
paper cap area, say .01 or .02 uf at 600V.

I'm sure I've also seen tubular Micamold caps. The tubular Micamolds seem
less disingenuous but are no more reliable.

Frank Dresser