I thought I would update on my hobby subject for tonight since I mostly worked on my Wurlitzer 200A electric piano instead of writing the post I meant to. I’m just now getting back into working on my electric piano after previously having zapped something on the board and not being able to get it working since. When I messed up last time I was actually trying to replace the capacitors and transistors that had dried up; I had thought these were causing considerable hum in the circuit. However, since deconstructing the piano I found a modification to the wiring scheme between the two speakers and the output headphone jack located at the bottom of the board. I found that on the headphone jack someone had wired in a simple RC circuit, presumably for filtering the headphone output. However, the small wiring scheme they used and meant to ground to the chassis had been disconnected, possibly by me. This floating output circuit could have been the problem all along! Only time will tell but I will feel silly if that was indeed the culprit.
Still, I always prefer a silly mistake that is found and easily corrected (with damage only to my ego) , as opposed to a difficult error that cannot be fixed or worse, found. See the pictures below of the destruction that has befallen my piano and hope that I can get humpty-dumpty back together again.
The main board, removed from the chassis. With new electrolytic caps.
The piano with the chassis and the board removed. The speaker assembly and the transformer are all bolted to the main chassis, which is convenient when you want to work on the action of the keys (how the hammer hits the tone bars).
The slew of new components I got in from my online order…and now may not need?
It’s not the wand, it’s the magician. In this case, the wand is a piece of junk soldering iron from Radio Shack. Maybe Santa will bring me an industrial voltage controlled soldering iron.