Radio repair

[supertntstar]

Hello,

I found an old Hitachi TRK-3D30E Radio/Boombox yesterday and I've been trying to repair it but with little success. The problem is that the speakers are too quiet and barely audible at max volume. I've tried using different speakers and a different power supply, but still no success.

Has anyone else had the same problem or any idea of what might be the cause?

 

[Unimportant]

I'd look for the AC coupling capacitors on the amplifier output. (between the amp and each speaker). Replace those first and give it a try. If they are indeed the culprit it might be wise to recap the whole thing.

[H713]

Good chance that it's a faulty cap somewhere, and if I were placing bets I'd put it on a small-value electrolytic coupling cap rather than the output cap to the speaker.

Small value electrolytics are the single most common thing I replace in older equipment. They look fine from the outside, and they'll measure fine for capacitance (often times, at least) but they'll have super high ESR (equivalent series resistance). I just fixed the SMPS for a Crest rackmount mixer. The problem? A 47 uF 16V cap with an ESR of almost 50 ohms.

As a rule, if I find one or more small-value electrolytic caps that have failed this way, I like to go through and replace them all. I don't usually replace large filter caps unless they're bad or likely to be bad.