Hi All,
I ran upon this article. It is about new capacitors, but the detrioration conditions seem to apply well to the capacitors we work with. Link is: http://www.electronicproducts.com/ShowPage1.asp?SECTION=1500&PRIMID=&FileName=vishay%2Enov2006%2Ehtml&Manufact=Vishay+Electronic+GmbH&ReturnLink=%2FSearch1%2Easp%3FManufacturer%3D%26Keyword%3DSelecting%2Band%2Bdesigning%2Bwith%2Baluminium%2Bcapacitors%26Slot%3D0%26StartNum%3D1%26stype%3D%26year%3D10&MonthYear=Nov+2006.

The good information is from the middle to the end of the section labeled 'Capacitor composition.' It describes how hot conditions, like an attic, increase Effective Series Resistance (ESR) through a drying out process. This is something intuitive, but is described here in a depth I haven't seen before. At the end it describes why you must not just plug in an old radio that has been on the shelf for a long time.
I have never done this, but have seen the results. It isn't pretty.

Let me know if this is of interest.

Best Regards,

Bill

"Let me know if this is of interest."

Yes, it was very interesting. I've saved the article as well as printed it out for future reference.

Thanks for the link

Dennis.

It's interesting that there are some electrolytics from the late 30's that still work fine, and some from the 60's that went poof a long time ago.
Maybe brand is a factor (Mallory cans vs. cheap cardboard). Also reputable manufacturers Hallicrafters, HH Scott, etc., seem to have a good track record for even vintage stuff, so maybe it's the brand/construction.
Then there's the question of:
Does a lot of use really wear out caps quickly?
Does a long period of disuse do the same?
What if you bought a brand new Mallory multi-element can cap NOS from 1949, would it last 20 years or more?
And of course I would suspect storage in a hot Florida attic as well as a subzero upstate NY garage would take its toll as well.

:It's interesting that there are some electrolytics from the late 30's that still work fine, and some from the 60's that went poof a long time ago.
:Maybe brand is a factor (Mallory cans vs. cheap cardboard). Also reputable manufacturers Hallicrafters, HH Scott, etc., seem to have a good track record for even vintage stuff, so maybe it's the brand/construction.
:Then there's the question of:
:Does a lot of use really wear out caps quickly?
:Does a long period of disuse do the same?
:What if you bought a brand new Mallory multi-element can cap NOS from 1949, would it last 20 years or more?
:And of course I would suspect storage in a hot Florida attic as well as a subzero upstate NY garage would take its toll as well.

Hi Frank,
The consensus of the List serve is to never use NOS filters. Usually this is a no brainer. The old capacitors usually take up space under the chassis, and are dried out dead anyway. The only time I have used NOS caps or retained capacitors that were there is when the radio had metal can, twist lock, capacitors that mount to the chassis. Typically these are of good quality and it is common to find them in good shape after 50 or 60 years. Moreover, placing a new capacitor under the chassis will take up space, which may be hard to find. These capacitors act as tie points, too, so replacing them may require installation of binding posts, a tedious chore.
HOWEVER, no mater how good these capacitors seem, they are far far less reliable than new ones. The frailties described in the article about new capacitors count double at least for these old one.
I had that hit home to me a few years ago. I fixed up a Zenith H723 AM/FM. The filter tested good, so I didn't replace it eventhough I replaced all the paper wax capacitors. It played great and got all the FM stations just as good as a new radio. I placed it in the bedroom. About a year later I came down with the flu. With a feaver of 104 I crawled over to the radio and turned it on and fell back into bed as the tubes warmed up. I expecting to hear my favorite radio station, instead I got HUMMMMM! Too exhausted to get up again I lay there with the sound of my folly in my ears. Echhh, certainly a low point in my life.

As for your quesitons:
Filter caps do not fail so much due to use, but due to age. Use actually helps the chemistry inside them stay in good shape.
Long periods of disuse can cause the chemistry in the capacitor, the electrolyte, to react in a disfavorable manner with the electrodes.
I would not expect a high quality capacitor from 1949 to last another 20 years. It may do that, but odds are against it. A new capacitor will last the 20 years hands down. If you really want to try an NOS capacitor, though, first charge it up with a low voltage, around 9 volts and leave it like that for a few hours before installation. That can help get the electrolyte get in shape.

Best Regards,

Bill Grimm

Bill,
On a recent rebuild, I made an error in measuring the original, so purchased an NOS canned unit for replacement. When it arrived, immediately took measurements, but it had a note attached that it had been re-formed to original value. Needles to say, it was well beyond its correct value + tolerance, but did discover my error in measurement of the original, and it was right on after all. Made several attempts with different voltages at restoring/re-forming the NOS part, but it still lies in its original carton in my junk drawer as unusable. Whats the secret to restoring/re-forming?

marv

::It's interesting that there are some electrolytics from the late 30's that still work fine, and some from the 60's that went poof a long time ago.
::Maybe brand is a factor (Mallory cans vs. cheap cardboard). Also reputable manufacturers Hallicrafters, HH Scott, etc., seem to have a good track record for even vintage stuff, so maybe it's the brand/construction.
::Then there's the question of:
::Does a lot of use really wear out caps quickly?
::Does a long period of disuse do the same?
::What if you bought a brand new Mallory multi-element can cap NOS from 1949, would it last 20 years or more?
::And of course I would suspect storage in a hot Florida attic as well as a subzero upstate NY garage would take its toll as well.
:
:Hi Frank,
: The consensus of the List serve is to never use NOS filters. Usually this is a no brainer. The old capacitors usually take up space under the chassis, and are dried out dead anyway. The only time I have used NOS caps or retained capacitors that were there is when the radio had metal can, twist lock, capacitors that mount to the chassis. Typically these are of good quality and it is common to find them in good shape after 50 or 60 years. Moreover, placing a new capacitor under the chassis will take up space, which may be hard to find. These capacitors act as tie points, too, so replacing them may require installation of binding posts, a tedious chore.
: HOWEVER, no mater how good these capacitors seem, they are far far less reliable than new ones. The frailties described in the article about new capacitors count double at least for these old one.
: I had that hit home to me a few years ago. I fixed up a Zenith H723 AM/FM. The filter tested good, so I didn't replace it eventhough I replaced all the paper wax capacitors. It played great and got all the FM stations just as good as a new radio. I placed it in the bedroom. About a year later I came down with the flu. With a feaver of 104 I crawled over to the radio and turned it on and fell back into bed as the tubes warmed up. I expecting to hear my favorite radio station, instead I got HUMMMMM! Too exhausted to get up again I lay there with the sound of my folly in my ears. Echhh, certainly a low point in my life.
:
:As for your quesitons:
: Filter caps do not fail so much due to use, but due to age. Use actually helps the chemistry inside them stay in good shape.
: Long periods of disuse can cause the chemistry in the capacitor, the electrolyte, to react in a disfavorable manner with the electrodes.
: I would not expect a high quality capacitor from 1949 to last another 20 years. It may do that, but odds are against it. A new capacitor will last the 20 years hands down. If you really want to try an NOS capacitor, though, first charge it up with a low voltage, around 9 volts and leave it like that for a few hours before installation. That can help get the electrolyte get in shape.
:
:Best Regards,
:
:Bill Grimm
:

Here's a great article:

http://www.vcomp.co.uk/tech_tips/reform_caps/reform_caps.htm

I was just asking for a 3rd opinion (I've seen differing ones) so it seems that "age" is the main culprit, "quality" helps, and being "used" rather than in storage is also a plus (aside hot attic or frozen temps).
I'm surprised that some real old ones still work, but on every radio that passes through my hands I'm now bypassing all the metal cans, plus changing all the paper caps. (Leaving the micas & ceramics in place)

:Here's a great article:
:
:http://www.vcomp.co.uk/tech_tips/reform_caps/reform_caps.htm
:
:I was just asking for a 3rd opinion (I've seen differing ones) so it seems that "age" is the main culprit, "quality" helps, and being "used" rather than in storage is also a plus (aside hot attic or frozen temps).
:I'm surprised that some real old ones still work, but on every radio that passes through my hands I'm now bypassing all the metal cans, plus changing all the paper caps. (Leaving the micas & ceramics in place)

____________________________________________________________________

At the bottom of the above mentioned article you will notice a date of 1946. Sixty years ago just after the war electrolytics were very expensive if you could find them at all, and reforming was an attractive solution. Today electrolytics are very inexpensive and available. It is just not worth the risk, and the time involved to attempt to reform electrolytics, their useful life span has been used up. Just replace them and you don't have to worry about your rectifiers and power transformer.

And don't forget to check those mica's and ceramics, we are starting to find lots of them bad also.

Dave

Easyrider,
Copied the article from the site you suggested, and thanks. I just opened a Philco 42-1008 today, so sure I'll need a lot of help. My first Philco restoration, and it sure looks to be a challenge. As I recall from past years, Philco always seemed to build top notch radios, and if the amount of hardware/components are any indication, this prize is no exception.

marv

::Here's a great article:
::
::http://www.vcomp.co.uk/tech_tips/reform_caps/reform_caps.htm
::
::I was just asking for a 3rd opinion (I've seen differing ones) so it seems that "age" is the main culprit, "quality" helps, and being "used" rather than in storage is also a plus (aside hot attic or frozen temps).
::I'm surprised that some real old ones still work, but on every radio that passes through my hands I'm now bypassing all the metal cans, plus changing all the paper caps. (Leaving the micas & ceramics in place)
:
:____________________________________________________________________
:
:At the bottom of the above mentioned article you will notice a date of 1946. Sixty years ago just after the war electrolytics were very expensive if you could find them at all, and reforming was an attractive solution. Today electrolytics are very inexpensive and available. It is just not worth the risk, and the time involved to attempt to reform electrolytics, their useful life span has been used up. Just replace them and you don't have to worry about your rectifiers and power transformer.
:
:And don't forget to check those mica's and ceramics, we are starting to find lots of them bad also.
:
:Dave

I only have 2 radios left to fix, one works fine but has a lot of paper caps so I'll need to replace about a dozen altogether, the very last one is an old battery radio with 1V tubes but also an AC cord and 117v rectifier, but with most all the wore rotting on it, so it will be a real challenge.
My point here, is that Antique Electronics is very good, but on 4 out of 5 orders, there was always 1 minor thing wrong. Now I have 10 .47 capacitors rather than .047's so that delays me until I can order more. Does anyone notice this about them? Don't get me wrong, I worship them for the stuff they have, and the prices are great.

:I only have 2 radios left to fix, one works fine but has a lot of paper caps so I'll need to replace about a dozen altogether, the very last one is an old battery radio with 1V tubes but also an AC cord and 117v rectifier, but with most all the wore rotting on it, so it will be a real challenge.
:My point here, is that Antique Electronics is very good, but on 4 out of 5 orders, there was always 1 minor thing wrong. Now I have 10 .47 capacitors rather than .047's so that delays me until I can order more. Does anyone notice this about them? Don't get me wrong, I worship them for the stuff they have, and the prices are great.

Hi Frank,
I have not had a problem with AES yet. Every now and then a supplier gets something wrong. I order from a lot of them. You may have happened to get them on bad days.
They should make it right, though.

Best Regards,

Bill Grimm

Yea, had a similar problem with AES. Sent wrong resistor on original order. I emailed them and they sent the same wrong resistor again. Got the right one on the 3rd attempt, but got 10 extra resistors free in addition to ones I ordered, even though it took about a week. Their OK I guess, and typically within 2 days shipping of my So. CA locale. PTOP is farther and longer, but being a "one man show", with an unbelievable collection of old and new, Gary's help is well beyond the norm, and I have only the highest regard for him.

marv

:I only have 2 radios left to fix, one works fine but has a lot of paper caps so I'll need to replace about a dozen altogether, the very last one is an old battery radio with 1V tubes but also an AC cord and 117v rectifier, but with most all the wore rotting on it, so it will be a real challenge.
:My point here, is that Antique Electronics is very good, but on 4 out of 5 orders, there was always 1 minor thing wrong. Now I have 10 .47 capacitors rather than .047's so that delays me until I can order more. Does anyone notice this about them? Don't get me wrong, I worship them for the stuff they have, and the prices are great.

:Yea, had a similar problem with AES. Sent wrong resistor on original order. I emailed them and they sent the same wrong resistor again. Got the right one on the 3rd attempt, but got 10 extra resistors free in addition to ones I ordered, even though it took about a week. Their OK I guess, and typically within 2 days shipping of my So. CA locale. PTOP is farther and longer, but being a "one man show", with an unbelievable collection of old and new, Gary's help is well beyond the norm, and I have only the highest regard for him.
:
:marv
:
::I only have 2 radios left to fix, one works fine but has a lot of paper caps so I'll need to replace about a dozen altogether, the very last one is an old battery radio with 1V tubes but also an AC cord and 117v rectifier, but with most all the wore rotting on it, so it will be a real challenge.
::My point here, is that Antique Electronics is very good, but on 4 out of 5 orders, there was always 1 minor thing wrong. Now I have 10 .47 capacitors rather than .047's so that delays me until I can order more. Does anyone notice this about them? Don't get me wrong, I worship them for the stuff they have, and the prices are great.

Hi Marv,
Could you post contact information on PTOP?

All the Best,

Bill Grimm

Playthings of the Past is good too, as mentioned above, but it's mostly older used stuff.

http://www.oldradioparts.com/

I've only ordered once from him, and all was fine except for a couple of 1/4" phono jacks, the ones he sent were Switchcraft alright, but the hole was a bit smaller so I couldn't use them, had to run to radio shack.

:Playthings of the Past is good too, as mentioned above, but it's mostly older used stuff.
:
:http://www.oldradioparts.com/
:
:I've only ordered once from him, and all was fine except for a couple of 1/4" phono jacks, the ones he sent were Switchcraft alright, but the hole was a bit smaller so I couldn't use them, had to run to radio shack.

Hi Frank,
Thank you for the tip.

Bill Grimm

Bill,
As I recall, its http//www.oldradioparts.com. Keep in mind that he requires that you check his inventory via the web and email your inquiry before ordering.
His all inclusive ordering instructions are on his site.

marv

::Yea, had a similar problem with AES. Sent wrong resistor on original order. I emailed them and they sent the same wrong resistor again. Got the right one on the 3rd attempt, but got 10 extra resistors free in addition to ones I ordered, even though it took about a week. Their OK I guess, and typically within 2 days shipping of my So. CA locale. PTOP is farther and longer, but being a "one man show", with an unbelievable collection of old and new, Gary's help is well beyond the norm, and I have only the highest regard for him.
::
::marv
::
:::I only have 2 radios left to fix, one works fine but has a lot of paper caps so I'll need to replace about a dozen altogether, the very last one is an old battery radio with 1V tubes but also an AC cord and 117v rectifier, but with most all the wore rotting on it, so it will be a real challenge.
:::My point here, is that Antique Electronics is very good, but on 4 out of 5 orders, there was always 1 minor thing wrong. Now I have 10 .47 capacitors rather than .047's so that delays me until I can order more. Does anyone notice this about them? Don't get me wrong, I worship them for the stuff they have, and the prices are great.
:
:Hi Marv,
: Could you post contact information on PTOP?
:
:All the Best,
:
:Bill Grimm

:Bill,
:As I recall, its http//www.oldradioparts.com. Keep in mind that he requires that you check his inventory via the web and email your inquiry before ordering.
:His all inclusive ordering instructions are on his site.
:
:marv
:
:::Yea, had a similar problem with AES. Sent wrong resistor on original order. I emailed them and they sent the same wrong resistor again. Got the right one on the 3rd attempt, but got 10 extra resistors free in addition to ones I ordered, even though it took about a week. Their OK I guess, and typically within 2 days shipping of my So. CA locale. PTOP is farther and longer, but being a "one man show", with an unbelievable collection of old and new, Gary's help is well beyond the norm, and I have only the highest regard for him.
:::
:::marv
:::
::::I only have 2 radios left to fix, one works fine but has a lot of paper caps so I'll need to replace about a dozen altogether, the very last one is an old battery radio with 1V tubes but also an AC cord and 117v rectifier, but with most all the wore rotting on it, so it will be a real challenge.
::::My point here, is that Antique Electronics is very good, but on 4 out of 5 orders, there was always 1 minor thing wrong. Now I have 10 .47 capacitors rather than .047's so that delays me until I can order more. Does anyone notice this about them? Don't get me wrong, I worship them for the stuff they have, and the prices are great.
::
::Hi Marv,
:: Could you post contact information on PTOP?
::
::All the Best,
::
::Bill Grimm

Hi Marv,
Got it. THanks!

Bill

In reference to my post of 03-07, and the Philco
42-1008. Started at the spkr, FC, VC, cone, and all were good. When I started in the power section, found a funky bakelite encased dual 0.01uf line filter. After unsoldering a couple wires, measured each side of the line to ground, and found about 300uuf. The only chassis connection was the mounting screw, which also held a small phenolic terminal strip. The ground terminal for the 2 caps was a small strap intended to go under the mounting screw. For some reason the strap was folded under the phenolic, and having never performed as intended. There is no evidence this set has ever been repaired, mutilated, restored etc, so it was a factory error. Both caps now measure 0.017uf to chassis.

marv

::Bill,
::As I recall, its http//www.oldradioparts.com. Keep in mind that he requires that you check his inventory via the web and email your inquiry before ordering.
::His all inclusive ordering instructions are on his site.
::
::marv
::
::::Yea, had a similar problem with AES. Sent wrong resistor on original order. I emailed them and they sent the same wrong resistor again. Got the right one on the 3rd attempt, but got 10 extra resistors free in addition to ones I ordered, even though it took about a week. Their OK I guess, and typically within 2 days shipping of my So. CA locale. PTOP is farther and longer, but being a "one man show", with an unbelievable collection of old and new, Gary's help is well beyond the norm, and I have only the highest regard for him.
::::
::::marv
::::
:::::I only have 2 radios left to fix, one works fine but has a lot of paper caps so I'll need to replace about a dozen altogether, the very last one is an old battery radio with 1V tubes but also an AC cord and 117v rectifier, but with most all the wore rotting on it, so it will be a real challenge.
:::::My point here, is that Antique Electronics is very good, but on 4 out of 5 orders, there was always 1 minor thing wrong. Now I have 10 .47 capacitors rather than .047's so that delays me until I can order more. Does anyone notice this about them? Don't get me wrong, I worship them for the stuff they have, and the prices are great.
:::
:::Hi Marv,
::: Could you post contact information on PTOP?
:::
:::All the Best,
:::
:::Bill Grimm
:
:Hi Marv,
: Got it. THanks!
:
:Bill

:Bill,
:On a recent rebuild, I made an error in measuring the original, so purchased an NOS canned unit for replacement. When it arrived, immediately took measurements, but it had a note attached that it had been re-formed to original value. Needles to say, it was well beyond its correct value + tolerance, but did discover my error in measurement of the original, and it was right on after all. Made several attempts with different voltages at restoring/re-forming the NOS part, but it still lies in its original carton in my junk drawer as unusable. Whats the secret to restoring/re-forming?
:
:marv
:
:::It's interesting that there are some electrolytics from the late 30's that still work fine, and some from the 60's that went poof a long time ago.
:::Maybe brand is a factor (Mallory cans vs. cheap cardboard). Also reputable manufacturers Hallicrafters, HH Scott, etc., seem to have a good track record for even vintage stuff, so maybe it's the brand/construction.
:::Then there's the question of:
:::Does a lot of use really wear out caps quickly?
:::Does a long period of disuse do the same?
:::What if you bought a brand new Mallory multi-element can cap NOS from 1949, would it last 20 years or more?
:::And of course I would suspect storage in a hot Florida attic as well as a subzero upstate NY garage would take its toll as well.
::
::Hi Frank,
:: The consensus of the List serve is to never use NOS filters. Usually this is a no brainer. The old capacitors usually take up space under the chassis, and are dried out dead anyway. The only time I have used NOS caps or retained capacitors that were there is when the radio had metal can, twist lock, capacitors that mount to the chassis. Typically these are of good quality and it is common to find them in good shape after 50 or 60 years. Moreover, placing a new capacitor under the chassis will take up space, which may be hard to find. These capacitors act as tie points, too, so replacing them may require installation of binding posts, a tedious chore.
:: HOWEVER, no mater how good these capacitors seem, they are far far less reliable than new ones. The frailties described in the article about new capacitors count double at least for these old one.
:: I had that hit home to me a few years ago. I fixed up a Zenith H723 AM/FM. The filter tested good, so I didn't replace it eventhough I replaced all the paper wax capacitors. It played great and got all the FM stations just as good as a new radio. I placed it in the bedroom. About a year later I came down with the flu. With a feaver of 104 I crawled over to the radio and turned it on and fell back into bed as the tubes warmed up. I expecting to hear my favorite radio station, instead I got HUMMMMM! Too exhausted to get up again I lay there with the sound of my folly in my ears. Echhh, certainly a low point in my life.
::
::As for your quesitons:
:: Filter caps do not fail so much due to use, but due to age. Use actually helps the chemistry inside them stay in good shape.
:: Long periods of disuse can cause the chemistry in the capacitor, the electrolyte, to react in a disfavorable manner with the electrodes.
:: I would not expect a high quality capacitor from 1949 to last another 20 years. It may do that, but odds are against it. A new capacitor will last the 20 years hands down. If you really want to try an NOS capacitor, though, first charge it up with a low voltage, around 9 volts and leave it like that for a few hours before installation. That can help get the electrolyte get in shape.
::
::Best Regards,
::
::Bill Grimm
::

Hi Marv,
The method of reforming in the later posting is more sophisticated than my 9 volt battery approach. Where I just left it for a few hours, they give time frames. If the capacitor has not come back in the time frame described, it is not recoverable.
Also, keep in mind trying to reform an open or dried out capacitor, will yeild results indicating that it has reformed quickly. It, however, will not have adequate capacitance, or have excessive series resistance (ESR).

If you really like the look of the dead capacitor, stuffing a new capacitor inside a gutted shell of the old one may be an option. Although time consuming you get the best possible performance and effect.

Best Regards,

Bill Grimm