Sterling, Iím more of a preacher/teacher than a musician; you know that
Geoff, I havenít figured out exactly how these things work yet, but there is a group of 555 based daughter boards that probably generate the base frequencies for each key in my machine. Theyíre the 12 vertical boards you can see on the right side of the first 2 photos. It looks like the keyboards are wired into those 555 boards. The board on the far end is the one that generates the E notes. Iíve already tried swapping the boards around but the problem still sticks with the E notes. I think the next step will be to get out the oscilloscope and start back tracking the frequencies out of the 555 timers.
I would bet many of the electrolytics have little capacitance left in them after 40 years so my bet is that one of them is causing my volume problems on the lower keyboard. I want to get this darn E note problem fixed before moving into the amplifier issue.
The sad thing about these wonderful old machines is they donít have much value right now in my area (the transistor based ones). Many times people just send them with the garbage man or sell them for a few dollars. Mine sold for $999 in 1974. That was a lot of money back then. I bought mine for $25 in a garage saleÖ.and I might have overpaid!!!