oldgearhog
Active Member
Since I have little time to work on this, it took forever but I finally finished a project that's been on my bench for way too long. I brought back to life a Nikko STA-2020, a little 10 wpc receiver. It seems to sound pretty good to me, but not as good as a little Pioneer SA-5200 in my other vintage system. It has a very basic tuner and not much in the way of features, just the usual BOTL buttons and knobs.
One channel was only playing a fuzzy low volume impression of real music while the other side worked fine. Mono sound ok, so I was puzzling over what was going on. No manual or schematic on line so I actually had to trace the circuit myself so see what was going on. That was a challenge by itself. Once that was done it was back to checking each output and input to isolate the problem. Also I am plagued by not having an oscilloscope that works. So finally, I narrowed it down to the preamp board and set about rebuilding it with all new caps and transistors. With that finished I was able to bring both channels back to their original glory!
I upgraded a number of caps using WIMA films where I could and Nichicon Golds for output coupling, putting larger ones in, and likewise for the main filter cap (only one, it's a single ended power supply) BTW, I had to increase the value and voltage quite a bit to get a cap big enough to fill the space where the old one was. Any thoughts on beating that problem?
And now with a good bath it looks like a mid-seventies receiver should and sounds not to bad to boot!
One channel was only playing a fuzzy low volume impression of real music while the other side worked fine. Mono sound ok, so I was puzzling over what was going on. No manual or schematic on line so I actually had to trace the circuit myself so see what was going on. That was a challenge by itself. Once that was done it was back to checking each output and input to isolate the problem. Also I am plagued by not having an oscilloscope that works. So finally, I narrowed it down to the preamp board and set about rebuilding it with all new caps and transistors. With that finished I was able to bring both channels back to their original glory!
I upgraded a number of caps using WIMA films where I could and Nichicon Golds for output coupling, putting larger ones in, and likewise for the main filter cap (only one, it's a single ended power supply) BTW, I had to increase the value and voltage quite a bit to get a cap big enough to fill the space where the old one was. Any thoughts on beating that problem?
And now with a good bath it looks like a mid-seventies receiver should and sounds not to bad to boot!
