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Those radios were prone to capacitors failing on the board due to excessive heat. When the capacitors go they take out the DM165 amp IC's for each channel (there are two). I would recap the amp/equalizer board if you have the time/know how - it is about ten bucks worth of parts.
Here is a write-up you can use for reference which also covers adding bluetooth to one of these old radios if you are so inclined. There are nice cheap 12V BT modules now on ebay that make the job much easier than what the author did creating a voltage regulation circuit, etc. With the eBay modules, you can just grab switched 12V from pins 1&2 on connector F as he shows and power the BT module.
A side note on the caps - the radio in the article is slightly different for a few cap values: I think yours will have 10 uf capacitors for C9 and C17 if I remember right and C19 & C20 will be 220 uf instead of 270 uf as listed in the write up. The best thing is just to inventory what you have on the board noting differences, order the replacements and then desolder/replace one at a time ONLY.
More info than you were looking for but hopefully useful to people here.
Here is a write-up you can use for reference which also covers adding bluetooth to one of these old radios if you are so inclined. There are nice cheap 12V BT modules now on ebay that make the job much easier than what the author did creating a voltage regulation circuit, etc. With the eBay modules, you can just grab switched 12V from pins 1&2 on connector F as he shows and power the BT module.
A side note on the caps - the radio in the article is slightly different for a few cap values: I think yours will have 10 uf capacitors for C9 and C17 if I remember right and C19 & C20 will be 220 uf instead of 270 uf as listed in the write up. The best thing is just to inventory what you have on the board noting differences, order the replacements and then desolder/replace one at a time ONLY.
More info than you were looking for but hopefully useful to people here.
