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RE: some issues you may encounter; I used to repair these things

-when I worked at the Allied RS Service dept.

The voltage regulator probably has been replaced. If not they can develop thermal intermittents.

The FM IF section employs 6-legged ICs that were a common failure issue. A number of generic replacements have existed over the years and work fine. The complaint is weak reception- not much inter-station hiss. The failing IC can be diagnosed by jumping a small disk cap (0.01uf is good) from input to output. If the FM reception improves you found the bad part.

I would not just replace the output coupling caps and power supply caps although that is a good place to start. Really any of the electrolytic caps in the signal path are suspect.

Its a good idea to put the unit on the bench and run a low distortion sine wave through it and just listen to the waveform at a low volume level. Quite often the bias was set a little low and crossover distortion can be heard. You can increase the bias a bit to just get rid of this. But some units will run hot depending on the device used in the circuit- there are variants! There is an electrolytic coupling cap at the input of the power amp board- replace it. Do not use tantalums!

The amp section employs thermisters for thermal feedback. This system works alright but is not as accurate as diode thermal feedback. Be careful if servicing the output section as the thermisters are fragile!

I would replace every electrolytic capacitor on the regulator board.

The output of the unit uses those goofy Pioneer connectors which look a bit like the prongs of an AC power cord but one prong is rotated 90 degrees with respect to the others. You can find these on ebay, search on Pioneer speaker plugs and a variety of them will show up.

The design of this circuit tends to make a bit of 2nd ordered harmonic which causes it to sound pretty smooth until you turn it up. But if you put it beside a good tube amp you'll probably not want to keep playing the Pioneer. In a nutshell at the time the semiconductors that were really needed to make a low distortion solid state amp really didn't exist. The THD of this unit is 1%...


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