Gentlemen:

I have been wondering about this question for a very long time.

Sometimes when I get an old radio chassis and try to run the unit, the output is quite distorted or low in volume.

After running or "burning in" the unit, sometime for a year or two, the unit comes up to normal output and/or the output is undistorted.

This effect happens long after the usual moisture in the caps would dry out.

Is there some dielectric aging effect being reversed in the caps? Are the units reforming?

Is the moisture being driven out of the carbon resistors over time?

As I stated this is a very long term recovery.

I find that in some cases no restoration is needed - only a burn in for an extended period of time. BUT it does NOT work in all cases.

Lou

Thanks
Lou Tramontozzi

:Gentlemen:
:
:I have been wondering about this question for a very long time.
:
:Sometimes when I get an old radio chassis and try to run the unit, the output is quite distorted or low in volume.
:
:After running or "burning in" the unit, sometime for a year or two, the unit comes up to normal output and/or the output is undistorted.
:
:This effect happens long after the usual moisture in the caps would dry out.
:
:Is there some dielectric aging effect being reversed in the caps? Are the units reforming?
:
:Is the moisture being driven out of the carbon resistors over time?
:
:As I stated this is a very long term recovery.
:
:I find that in some cases no restoration is needed - only a burn in for an extended period of time. BUT it does NOT work in all cases.
:
:Lou
:
:Thanks
:Lou Tramontozzi
:

I would not expect anything that comes up as often as you indicate, but maybe a rare problem. Hopefully you replace old elctrolytic capacitors and audio coupling capacitors as a matter of course. Defective audio coupling caps, or the power tube bypass electrolytic capacitor (if any) could cause distortion / low volume, and I have seen electrolytic capacitors reform over time. You could spot a problem by taking voltage readings. How / where have the radios been stored? Is there rust, dirt, bug poop, dead silverfish, roaches,etc. in the voice coil gap or elsewhere? (Yes, I have seen that and worse). Anything keep the voice coil from moving freely, such a dirt, dead bugs, something loose, etc; might eventually work loose, or even make a hole in the speaker diaphram that you would not notice at low or moderate volume. Do the volume controls work properly, or are they scratchy? Is your incoming line voltage normal or low? Did somebody use the wrong tubes, such as a 50L6-GT where it should be a 35L6-GT?
PLEASE at least check any old radio first, and replace old electrolytic capacitors, before plugging in any old radio. My counterparts and seen numerous radios ruined because someone just plugged it in to see if it works - and there went the power transformer, a tube or two, and other stuff. Ed M

::Gentlemen:
::
::I have been wondering about this question for a very long time.
::
::Sometimes when I get an old radio chassis and try to run the unit, the output is quite distorted or low in volume.
::
::After running or "burning in" the unit, sometime for a year or two, the unit comes up to normal output and/or the output is undistorted.
::
::This effect happens long after the usual moisture in the caps would dry out.
::
::Is there some dielectric aging effect being reversed in the caps? Are the units reforming?
::
::Is the moisture being driven out of the carbon resistors over time?
::
::As I stated this is a very long term recovery.
::
::I find that in some cases no restoration is needed - only a burn in for an extended period of time. BUT it does NOT work in all cases.
::
::Lou
::
::Thanks
::Lou Tramontozzi
::
:
:I would not expect anything that comes up as often as you indicate, but maybe a rare problem. Hopefully you replace old elctrolytic capacitors and audio coupling capacitors as a matter of course. Defective audio coupling caps, or the power tube bypass electrolytic capacitor (if any) could cause distortion / low volume, and I have seen electrolytic capacitors reform over time. You could spot a problem by taking voltage readings. How / where have the radios been stored? Is there rust, dirt, bug poop, dead silverfish, roaches,etc. in the voice coil gap or elsewhere? (Yes, I have seen that and worse). Anything keep the voice coil from moving freely, such a dirt, dead bugs, something loose, etc; might eventually work loose, or even make a hole in the speaker diaphram that you would not notice at low or moderate volume. Do the volume controls work properly, or are they scratchy? Is your incoming line voltage normal or low? Did somebody use the wrong tubes, such as a 50L6-GT where it should be a 35L6-GT?
:PLEASE at least check any old radio first, and replace old electrolytic capacitors, before plugging in any old radio. My counterparts and seen numerous radios ruined because someone just plugged it in to see if it works - and there went the power transformer, a tube or two, and other stuff. Ed M
:
:
Ed:

I have restored many a radio in my day, and I ALWAYS take precautions before plugging anything in.

After the usual B+ checks, power transformer and filter cap heat, etc, and running the unit with a series fuse, ( I DO replace the electrolytics if necessary up front) I have noticed that some radios just RECOVER BY THEMSELVES!! after some distortion.

Maybe just lucky or a long term effect?

Thanks
Lou

:::Gentlemen:
:::
:::I have been wondering about this question for a very long time.
:::
:::Sometimes when I get an old radio chassis and try to run the unit, the output is quite distorted or low in volume.
:::
:::After running or "burning in" the unit, sometime for a year or two, the unit comes up to normal output and/or the output is undistorted.
:::
:::This effect happens long after the usual moisture in the caps would dry out.
:::
:::Is there some dielectric aging effect being reversed in the caps? Are the units reforming?
:::
:::Is the moisture being driven out of the carbon resistors over time?
:::
:::As I stated this is a very long term recovery.
:::
:::I find that in some cases no restoration is needed - only a burn in for an extended period of time. BUT it does NOT work in all cases.
:::
:::Lou
:::
:::Thanks
:::Lou Tramontozzi
:::
::
::I would not expect anything that comes up as often as you indicate, but maybe a rare problem. Hopefully you replace old elctrolytic capacitors and audio coupling capacitors as a matter of course. Defective audio coupling caps, or the power tube bypass electrolytic capacitor (if any) could cause distortion / low volume, and I have seen electrolytic capacitors reform over time. You could spot a problem by taking voltage readings. How / where have the radios been stored? Is there rust, dirt, bug poop, dead silverfish, roaches,etc. in the voice coil gap or elsewhere? (Yes, I have seen that and worse). Anything keep the voice coil from moving freely, such a dirt, dead bugs, something loose, etc; might eventually work loose, or even make a hole in the speaker diaphram that you would not notice at low or moderate volume. Do the volume controls work properly, or are they scratchy? Is your incoming line voltage normal or low? Did somebody use the wrong tubes, such as a 50L6-GT where it should be a 35L6-GT?
::PLEASE at least check any old radio first, and replace old electrolytic capacitors, before plugging in any old radio. My counterparts and seen numerous radios ruined because someone just plugged it in to see if it works - and there went the power transformer, a tube or two, and other stuff. Ed M
::
::
:Ed:
:
:I have restored many a radio in my day, and I ALWAYS take precautions before plugging anything in.
:
:After the usual B+ checks, power transformer and filter cap heat, etc, and running the unit with a series fuse, ( I DO replace the electrolytics if necessary up front) I have noticed that some radios just RECOVER BY THEMSELVES!! after some distortion.
:
:Maybe just lucky or a long term effect?
:
:Thanks
:Lou
:
Lou,
Sorry, my comments were meant more for the inexperienced who read this forum than for you, and were unappropriate as a continuation to the thread you started. I have been thinking intently about the situation you describe, and about the only other thing I can think of is that somehow the Q or tuning of the IF transformers is 'off', and maybe thay dry out or something when the radio is operated. Maybe something in a tuned circuit is warped, but I cannot explain the recovery. And the fact that your experience includes several radios would indicate more than just a fluke. Again my apologies; I just finished cleaning out a radio filled with mouse poop that someone had found in their grandmothers attic. He had plugged it in without looking inside first, to see if all the tubes lit up. When the set smoked, he thought it was the disintergrated old rubber line cord, so he cut it off outside the chassis, attached a cord from a Christmas tree light, taped it up with masking tape, and plugged it back in again - and WALKED AWAY, to give the tubes time to warm up!. His living room still smells like frying tar. Ed M

There would be various reasons a radio might start sounding better after playing it for some time. I don't know why anyone would put up with poor performance and bad sound for a " year or two " in hopes that it will fix itself. All the reasons mentioned about old capacitors self repair, and resistors finally drying out, voice coil rubbing the pole piece finally wearing in after extended play time. Overall I think that to repair/restore the radio first off would be the thing to do. Knowing that it is now dependable and top performance is what I am sure most of us do.

:There would be various reasons a radio might start sounding better after playing it for some time. I don't know why anyone would put up with poor performance and bad sound for a " year or two " in hopes that it will fix itself. All the reasons mentioned about old capacitors self repair, and resistors finally drying out, voice coil rubbing the pole piece finally wearing in after extended play time. Overall I think that to repair/restore the radio first off would be the thing to do. Knowing that it is now dependable and top performance is what I am sure most of us do.
:Oh sure

This was basically something I have noticed over the long term. When I started fixing sets ( a VERY long time ago) all I knew was to keep playng them to see what would happen ( again after checking the power supply). I DID notice that after some time some radios would indeed "fix" themselves and run well again.

I am wondering if the issue is with capacitor repolarization and/or heat drying out resistors and getting them back to thier proper values ( only Carbons).

Just an observation - wondered if anyone else has seen this.

Lou