Since the day I was born, this amplifier has been a staple of my living room. Here I am as a toddler standing on my tippy-toes playing with it. A few years later I remember making mix tapes by dubbing from my parents’ records or CBC radio. Sometime in the late nineties, it developed a nasty audible distortion, so it got replaced with a newer one that is black, made of plastic, and has a great many features. A few years ago I dug it out of my parents’ basement and toted it all the way to Vancouver. I tried to have it fixed, but our society doesn’t really do that anymore, and so it’s sat.
It is therefore with great pride that I fixed it today.
I’d been vaguely familiar with the fact that capacitors degrade over time, and that a lot of failing consumer electronics can be revived by replacing bad caps. I remember people at Free Geek buying up non-working LCD monitors, putting a couple dollars worth of new caps in them, and reselling them for a well-earned profit. I’m also vaguely familiar with the practice of upgrading capacitors and resistors in audio gear to vastly improve their performance.
To diagnose this amp’s troubles, I used a borrowed K-7204 ESR meter and checked all the capacitors. The great thing about ESR meters is that you can test components in-place. The Sansui AU-2200 has a fantastic service manual with diagrams and component lists, so testing was a snap. I started with the big capacitors on the power amp board, and worked down to smaller ones. Remembering that the problematic distortion always corresponded to high-power bass frequencies, it stood to reason that the big caps might be at fault.
Sure enough, all the biggest caps had terribly high ESR readings, so I biked to Lee’s Electronics and bought replacements. Smaller capacitors have a higher expected ESR, so it’s less obvious when they’re bad. I probably should have just replaced all of them (it’s nearly 30 years old!) but I wasn’t sure so for now I just did the obvious ones. I also opted for the garden-variety Nichicon VZ line instead of the “audio-grade” Panisonic FM series, because the former were available locally and my goal was just to get the thing working. They should be at least as good as the original, and probably way better.
I am beyond pleased that I was able to fix it. It cost around $10 and an afternoon, and I learnt a lot.