This venerable Sony preamp was seen at Rain City Audio last September 2015 when it came in for an evaluation. That check-up revealed a clean bill of health at the time, but over the past several months of active service, the original components worn down and started creating problems.
This preamp is very overbuilt, with the different circuits on modular plug-in cards for easy removal.
Component replacement was uneventful for the plug-in cards, although there were some strange value capacitors that I’ve never run into before, like some 150 uF capacitors, and a set of capacitors rated at 3.15V.
There were 4 more capacitors hidden on the phono amplifier board behind the main panel:
Time to replace the main electrolytic capacitors as well. The originals were replaced with new long-lifetime, high-ripple Kemet models made in the EU, and upgraded to screw terminals.
Now for checks and adjustments:
Everything cleaned up and came into spec nicely! Time to measure with the Audio Precision System One.
Overall frequency response looks great, and zoomed in, the channels are ~0.3 dB separated from each other. Very close!
And look at that almost perfectly matched RIAA curve for each channel after service.
Quite a few parts came out of this one! It’s going to sound fantastic for a long time to come.