Hi everyone,
I just picked up this old gem at Goodwill a few days back. When I brought it home and fired it up, only the right channel was emitting sound. I checked my connections and retested. Same result.
After a little bit of tinkering with knobs and inputs, I decided to take a look under the hood. The strange thing that I noticed is that there is some left channel audio emitting from the same area as the power caps on the main board inside the unit. I haven't tested them, but I bought some new ones from Mouser and plan on replacing them. It was less than $10 for the pair, so I figured why not.
Is there something else that I should check out? What could be making that sound? A transistor? It's the left channel audio that is coming out of the board. It sounds like one of those oldschool white mono earbuds from the '60s or '70s.
Any help or suggestions would be greatly appreciated.
Thanks!
I just picked up this old gem at Goodwill a few days back. When I brought it home and fired it up, only the right channel was emitting sound. I checked my connections and retested. Same result.
After a little bit of tinkering with knobs and inputs, I decided to take a look under the hood. The strange thing that I noticed is that there is some left channel audio emitting from the same area as the power caps on the main board inside the unit. I haven't tested them, but I bought some new ones from Mouser and plan on replacing them. It was less than $10 for the pair, so I figured why not.
Is there something else that I should check out? What could be making that sound? A transistor? It's the left channel audio that is coming out of the board. It sounds like one of those oldschool white mono earbuds from the '60s or '70s.
Any help or suggestions would be greatly appreciated.
Thanks!
Transistors, particularly TO3 styles can emit "sound". The mechanism by which they do that is a little unclear. Also wirewound components such as coils can emit audio in response to the current flowing.
If you can "hear" audio from the left channel components in the amp and nothing from the speaker then I suggest looking for something simple such as an open circuit condition somewhere between the amp output and the speaker.
If you can "hear" audio from the left channel components in the amp and nothing from the speaker then I suggest looking for something simple such as an open circuit condition somewhere between the amp output and the speaker.
Hey Mooly -
Thanks for the reply and the info. I appreciate it.
It sounds like from what you're saying and from some searching that the left-channel transistors might be the culprit. I'll do a complete break-down of it over the weekend instead of just taking the lid off. Excited to dive in and fix it! Thanks again!
Cheers,
Kevin
Thanks for the reply and the info. I appreciate it.
It sounds like from what you're saying and from some searching that the left-channel transistors might be the culprit. I'll do a complete break-down of it over the weekend instead of just taking the lid off. Excited to dive in and fix it! Thanks again!
Cheers,
Kevin
I wouldn't say the culprit. If you can hear audio from them it sounds like they are working.
As always check the basics such as DC offset of that channel. Make sure that the speaker relay is closing OK and that there is continuity from output, through the speaker and back to ground.
As always check the basics such as DC offset of that channel. Make sure that the speaker relay is closing OK and that there is continuity from output, through the speaker and back to ground.
Turns out that a closer look at the fuses inside revealed a blown fuse. After replacing it, the left channel works perfectly.
Thanks for the suggestions!
Thanks for the suggestions!
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