Hello all, wanted to go ahead and provide some documentation on another Yamaha C-2a restoration. This unit was brought to be with the notorious popping issues that seem to plague these units. At the time I wasn't entirely sure just how deep I'd need to get into this unit, so I started with a recap and replacement of some of the trim pots. I quickly found out that the popping issue was most definitely semiconductor related, and also discovered a bias issue on a cold startup. This was later found to be the result of damaged 2SC1953s in the equalizer section. In the end, all electrolytic caps were changed, although not really necessary, the large film caps were also changed, the VD1212 double diodes were replaced with 2 1N4148s in series, all resistors on the tone board were replaced with dale RN60D series resistors, some of the trim pots were replaced with Bourns replacements (note: replacements for all trim pots are noted in the BOM), and the vast majority of the transistors in the unit with exception of the dual FET packages and the MC amp transistors were replaced with matched replacements. The replacement of the majority of these transistors was not all that necessary as the 2SC1953s seemed to be the main issue, but I did notice some slight improvements in the final DC offset swing, which was very large to begin with. I'll attach a complete BOM below with all the parts used in my unit, hopefully this will be beneficial to others. Special thank you to Milo63 who went through the hell of taking note of all the resistor values on the tone board. I did make sure that these values aligned with those on my unit, and made note in the BOM of any difference in values between his findings and my own. The replies from me following this initial post will document some of the work I did to my unit.
To each his own..