I've had an Abbotwares Z477 Horse radio for years, given to me by my grandmother. It did not work all this time because the on/off switch was broken. I recently was able to buy the 'guts' (working) of this radio. I swapped the 'guts' in the chassis, planning on doing a lot of work on the original radio.

I was playing the radio one day, and after about 30 minutes or so I heard a POP. It did not seem to affect anything, but I turned it off. After it cooled down a bit, I opened it up and could find nothing obviously wrong. Since then, however, I seem to notice a hum when it is playing. I do not remember hearing it before the pop. It is not noticable when a station is coming in loud and clear, but anytime between stations or when it is not very clear.

Am I nuts or did something change?

Many of the caps were replaced in this radio, but not all. Some appear to be original. Should I start with changing particular caps? I have replacement tubes, but do not want to change them unless necessary.

The schematic for this radio resembles this model by a different company: http://www.nostalgiaair.org/PagesByModel/751/M0009751.pdf

They both use the same tubes and similar cap voltages, etc.

I'm just wondering where I should start. Any help would be appreciated. Thanks!

Sounds like the line bypass cap let loose. If you are going to use this radio replace the filters and caps, otherwise make it a shelf queen.

Dave
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:Sounds like the line bypass cap let loose. If you are going to use this radio replace the filters and caps, otherwise make it a shelf queen.
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:Dave
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Thanks for the info. Once the Fall gets here I'll take some time to work on the replacements.