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Pioneer SX-110 Receiver rebuild

Posted by TimeConstant on August 19, 2014 at 03:34:30

I recently completed the end of a long journey, with the satisfaction that an old Pioneer tube receiver is once again playing, and it is the amplifier with the lowest noise of all amps I currently own.

This was almost a lost project as 10 years ago while troubleshooting I removed two of the little black square box six lead Tone Modules. As with every thing I do I made a diagram of where each lead is connected to.

Well somehow the diagram was lost and the original schematic does not provide the module identification lead numbers.

One attempt of mine was to biuld two modules on perf-board, and it failed to work.

I even bypassed the Tone Control section and had the SX-110 playing for a few month's, with the gain scaling affected by the lack of the module in the audio chain.

Then, one day, I found the drawing among old papers and notes. I jumped up and down, pulled the little soapbox modules out of storage and installed them back into the amplifier.

This project has been many many hours of work, I have now the amplifier playing magnificently, yet the Phono and FM sections are still not performing well.

But I can attest to the fact that the 7868 Electro Harmonix tubes are wonderful, the bloom and presence they provide makes this a great amplifier to use as a Stereo Video entertainment piece.

I put my ear right up against the speakers and hear nothing, unless of course I turn up the volume past 3'Oclock and then a slight hum/buzz will leak out, but still, this amp has a great clean and open bottom end.

The only complaint with these old Japanese amps is the large amount of ELNA PIO caps that dry out, along with a substantial amount of small Suzuki tubular wire wound resistors that drift or crack.

All of the Green-Drop coupling caps have been changed in the Audio chain, so my next efforts will be to update the FM section and end with revamping the Phono section.

Anyone needing advice or help with this old tube receiver just send me a mail.

I tend to stay away from old Tube Receivers as they require the most amount of dedication and time to restore.

Hope all of you are well and warming up the tubes for Fall and Winter.

Happy toobing.

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