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SX-650 woes (left channel distortion when connecting speakers)

Gotaj

Gotaj

New Member
Hello everyone. I've been reading these forums for a while, ever since I picked up a dirty SX-650 for 35 euro (~40 USD) a couple of months ago. I've no experience working on amps but was hoping to get into the hobby since I love the look and sound of vintage audio gear, so I took my chances. The forum really is full of good information but I'm stuck anyway, so here goes.

I thoroughly cleaned the amp and it is looking great now. I inspected it visually and saw no damage, except for the three incandescent bulbs that illuminate the radio dial. They were burnt but that's an easy job. I tested the amp with my headphones and it worked perfectly on all inputs.

However, the trouble came when I started hooking up speakers. The speakers themselves are mint, I've verified this multiple times. When I add speakers to the left channel (either A or B), the channel is noticeably low in volume and heavily distorted. This happens with all inputs and even in my headphones. I can listen AUX, phono or FM and it will sound absolutely great until I connect even one speaker to the left channel. I have tried setting the amp to mono but that doesn't solve the problem. I will say that listening on extremely low volume seems to get rid of the distortion.

I coughed up ~26 USD for a can of Deoxit D5, but it did not help the issue, unfortunately. I'm sure it will be helpful for other projects.
I tried tapping the relay from different directions, that did also not make a difference.
I've got a multimeter coming in off Amazon, but I haven't tested anything in that way so far.

Any ideas what it could be? Thank you kindly for you help.
 
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Welcome Aboard!

There are a lot of possibilities. Once you receive your meter and familiarize yourself with it, we can start checking some items.

In the interim, did you clean the speaker switch? Also, there is a speaker relay in the SX-650. If you can access the relay and remove the cover, it would be good to clean/burnish the contacts to eliminate that as a possible point of signal loss.
 
Thanks for the welcome Watthour. I have cleaned the speaker switch thouroughly, but I have not removed the relay cover to clean it on the inside. I'll try that next.
Zebulon, thank you for the link. I hadn't found that thread yet.
 
Can anyone confirm if it is necessary to loosen all the wires in the vertical PCB to get to the relay? It is really hard to reach...
 
Crazy. I'm having the same issue with my left speaker as well. Sometimes it works just fine after a while so I suspect it's the speaker relay. I'm totally new to all this and that stack on top of it is intimidating. Can I just remove the stack to get to the relay and try to clean them that way?
 
You should be able to lean the power board out enough to access the power amp board. It's still awful access, but should work.
 
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