Good evening Fellow Collectors of Things That Glow When Used

I am helping a friend in AZ (I live in CT) with an AK-9 he has had passed down to him from his grandfather.
he has gotten the radio working with a PS and was pleased with it. Now it works for a short time and then dies. He has determined that the amp B+ also drops considerably as this occurs. Tubes have been ruled out.

Although I am not an AK collector, looking at the schematic for a AK-10 (cannot find one for a AK-9) I see a .2 mfd cap across the B+. I am suspecious of this as it would seem a bad xfrmr would manifest itself as open.

Attached are pictures of the unit. Is this the .2 cap on the bottem (the black rectangle in the pocket in the wood). Can someone tell me what these parts are? The pictures are on this web site.

http://pages.cthome.net/nord/AK-9.htm

Thanks

--
Carl
WA1KPD
Visit My Boatanchor Collection at http://pages.cthome.net/nord/wa1kpd.html

Hi,
The filter capacitor is the likely culprit- as you suspect. From the look of the bottom, the item you are trying to show is a filter capacitor of that era.

With it operating for a time, and then acting up is more suggestive of something heating and shorting out as internals expand (since you ruled out the tubes already).

Someone who may be of some assistance in locating a schematic is:
http://web2.airmail.net/vanew/
For some specifics of the differences between the Models 9 and 10, check out here:
http://www.sparkmuseum.com/BREADBD.HTM

Something I have not yet tried with some of those early style caps, mostly for a lack of time, would be to immerse the cap completely in a mineral oil, or castor oil bath, and then evacuate the air from the vessel for a few days on the same order as you would draw down an air conditioning system (-26 inches of mecury).

It would be a bulky apparatus, and there is no guarentee of quality, but if it were to work on 50% of those caps tried, it would certainly justify it in protecting values and originality.

Otherwise, it is not impossible to artfully hide a replacement cap underneath the exising one.

:Good evening Fellow Collectors of Things That Glow When Used
:
:I am helping a friend in AZ (I live in CT) with an AK-9 he has had passed down to him from his grandfather.
:he has gotten the radio working with a PS and was pleased with it. Now it works for a short time and then dies. He has determined that the amp B+ also drops considerably as this occurs. Tubes have been ruled out.
:
:Although I am not an AK collector, looking at the schematic for a AK-10 (cannot find one for a AK-9) I see a .2 mfd cap across the B+. I am suspecious of this as it would seem a bad xfrmr would manifest itself as open.
:
:Attached are pictures of the unit. Is this the .2 cap on the bottem (the black rectangle in the pocket in the wood). Can someone tell me what these parts are? The pictures are on this web site.
:
:http://pages.cthome.net/nord/AK-9.htm
:
:Thanks
:
:--
:Carl
:WA1KPD
:Visit My Boatanchor Collection at http://pages.cthome.net/nord/wa1kpd.html