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Another Pioneer SX-434 Repair Thread

Can you tell us how you're feeding the signal in and what the level is? Aux input? 150mV is what you usually think of as the normal line level signal. That should get you to full output about the time you get to full volume. Lots of sources have a stronger signal than 150mV though, and that will clip before you get to full volume. So what you're seeing may be normal but it does look like you're still missing the top part of your sine wave. Not sure if you've replaced that resistor yet.

You can measure the output power a couple ways. The easiest is probably to use a meter set to AC volts. Or you can read the voltage off your scope and do math to get RMS volts and convert to watts. If you're getting full power output before clipping happens, then everything is working like it should.

That thick trace can be normal at really low levels. Scopes can be a bit noisy when looking at small signals. The thickening at the top and bottom could indicate a bit of distortion or oscillation but probably just noise? You can shorten the time scale to stretch that signal out and see if it's a just noise or if it's a higher frequency oscillation or harmonic (it'll look like another sine wave riding on your lower frequency sine wave).
 
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For measurements I'm using a BK Precision 3011b signal generator 1k sine wave going into the Aux input. I just measured the BK output as 500mv AC and 33mvDC with amplitude at Min. Same DC but 7.4vAC at Max Amplitude. That seems pretty hot going in which is why it might be clipping early.

Ear tests have been via PC headphone output into the Aux In and then switching to FM radio to compare levels.
 
If you turn the signal generator all the way down, it'll be ok. Some sources put out about that kind of signal so it won't hurt anything. Just have to be aware that you'll get clipping before you get to max volume.
 
When you're ready to measure the power output of the receiver, you can do it the same way. RMS Volts squared, divided by the dummy load resistance will give you watts. If you're getting the rated output power before clipping happens, it's working like it should.
 
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