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Pioneer SX850 Amplifier Issue

My amp has been working fine since I cleaned it. It just stopped producing sound a few days ago. The tuner still works, and all the connections are secure. It powers up, but no sound. Any ideas about what to check would be appreciated.

Thanks



Pioneer SX850 Amplifier Issue

A bad regulator transistor (12VDC) will kill all sound, as well as produce a dead tuner (no Signal strength, Center tune, or Stereo indicator.) on a SX-850

First check if the protect relay is engaging within 10 seconds after powering on (You can hear the click)
If it is engaging, tap the relay to see if you get any sound (in tuner mode). The contacts could be dirty.
If the relay is engaging, and you still can't get any sound, the problem is probably before the power stage, possibly some of the switches if you had cleaned them with cleaners not safe for plastic.
If the relay is not engaging, your problem is with one of the power stages, or with the protect circuit. Check for shorted output transistors. Also check pin 12 and pin 27 on the power board and make sure they read "0" volts. If one of the pins has DC volts on it, then the channel in line with the corresponding pin has other bad components. If you have no shorts or opens, and "0" volts on the 2 pins, the problem is on the protect board. If one of the pins has DC volts on it, then the channel in line with the corresponding pin has other bad components. The small signal transistors, diode, and even leaky caps on the protect board can all cause issues. look for a changing DC voltage on either the base, or collector of these small transistors. If you find a transistor that has a rock solid DC voltage on the base, and the collector is a changing DC voltage, the transistor could be noisy and cause the problem of the protect circuit staying on.
Let me know how you work out with this.
Tom

Pioneer SX850 Amplifier Issue

Check your regulator transistor; it may be open.