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Old 7th November 2008, 10:51 PM   #1
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Default fuzzy left speaker

I have a sansui A-1100r amplifier from the 80's that I just got and the left speaker sounds fuzzy. When music is playing there is a noticeable fuzzy sound to it and when music is not playing there is a quiet fuzzy noise coming out of the left speaker.
I tried plugging the right speaker into the left speaker slot and there is the same problem, so it is not the speaker. The amp also has a spot for a "b" set of speakers and I tried using those, but the same problem persist. Could the pinch type connectors on the back of the amp be bad or is it something else? I don't know if it is just me, but the sound seems to get better, almost perfect in the left speaker after the amp has been on for about 10 minutes.
There is also a fan in the back of the amp that you can see through the vent on top. I have only had the amp on for about 20 minutes, but the fan is not on. Does the amp need to heat up for the fan to turn on or should it be on whenever the amp is on?
The amp is in perfect shape on the outside and looks to be in perfect shape on the inside (no dust or marks on the boards inside)
Thank you for reading!
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Old 7th November 2008, 11:00 PM   #2
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almost 30years old and still working - sort of.
Pretty impressive.

With an amp that old you kinda wonder if some of the electrolytic caps have dried out.

Sounds like distortion of some kind and with a temperature dependence (do any parts get warm after 20mins?) it sounds like a bias problem.

If you have a scope you can trace the signal from the input and see where things go bad. If not then a voltmeter comparing voltages on key transistors between the good and bad channels may shed some light. Start at one end and work back. Take notes.

A schematic would be a lifesaver here. Have you googled?

P.S. fan is very likely temperature controlled.
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Old 7th November 2008, 11:56 PM   #3
jaycee is offline jaycee  United Kingdom
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Almost certainly a sign of a thermal issue.. as Iain says either a bias issue or a now-stuffed electrolytic cap.
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Old 8th November 2008, 02:52 AM   #4
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I took the cover off the amp again and and it looks like the large (I believe they are aluminum electrolytic capacitors) have leaked. There is a purple dried up chemical around the bottom of them. There are two of them next to each other in the amp and I think that one is for right and one is for left and the one that is for left has leaked enough not to make it work very good. Am I correct in assuming that these could cause the problem with the left speaker?
The label on the capacitors is
Nippon
Chemi-Con
CE 85*C
80v8200uF(M)
Negative Black

The * should be a degree sign and the u should be the greek symbol that looks like a u, I believe for capacitance rating.

If this is the problem do you know where I can get these capacitors and if the one under results at the bottom of the list in the posted link is the correct one? How difficult are these to install?

http://www.chemi-con.co.jp/english/catalog_e/top.html

Thank you for the help!
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Old 8th November 2008, 04:46 AM   #5
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not necessarily. They used to glue the larger caps to the board to stop them pulling the pads off the board in shipping. I've seen the spectrum of colors used.

They are probably the PSU caps, one for +ve rail, one for -ve rail. Put your meter on one at a time and check DC voltage (should be less than 80V, maybe as low as 40V) then switch to AC volts and measure the ripple. More than a volt or two of ripple is suspect.

BTW I don't think this is the problem.
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