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Old 08-23-2011, 03:43 PM
kidd kidd is offline
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Location: Chatham, Ontario, Canada
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Pioneer SX-950 1976 to 1977 vintage

Hello, trying to get some information as to the problem with this stereo, turns on plays music on the AM side and then when I go to the FM it plays music and if I try to increase the audio level it activates the protect relay and shuts down. If I reduce the volume and switch off then back on it will play again, then the same thing happens, the FM light as well as the Stereo light are not coming on neither, but if I switch between Stereo and Mono there is a definite difference in sound, FM more spacious then Mono, where should I start to look, also need the schematic if anybody has one that I could get a copy of. I have heard that it might be the relay itself and that it should be cleaned the contacts that's I have found out so far, thanks.
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Old 08-23-2011, 04:24 PM
bob91343 bob91343 is offline
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Not the relay. Apparently the protection circuit needs some attention or, even more likely, one or both amplifiers has enough offset to make the protection activate.

You might find the service manual on Audiokarma. It's not a rare model.

As for the stereo lamp, it may be burned out. Check with an Ohmmeter.
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Old 08-23-2011, 04:38 PM
kidd kidd is offline
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Ok will do, and thanks.
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Old 08-23-2011, 04:45 PM
kidd kidd is offline
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So is that something that a person with no electronic test gear could try to adjust as far as the offsets go or is that for a repair shop? It says the site is down for the time being Audiokarma so still in a bind as far as service manual goes.
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Old 08-23-2011, 07:39 PM
bob91343 bob91343 is offline
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Don't mess with it unless you know what you are doing. It's too easy to short something and blow it up, even for many experienced technicians.

I have the SX-950 service manual on disk but it's about 15 MB.
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Old 08-23-2011, 07:44 PM
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CoogarXR CoogarXR is offline
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Are you sure your speakers are the correct impedance? It almost sounds like you have a 2 ohm load or something.

I have also heard of some of these STK-based receivers having the thermal paste break down. They heat up, shut down, cool off, start back up, etc. That might be something to check too.
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