1. the caps I got (From Mouser.com) were all Nichicon. I've installed most of them on the main board (not all though - ordered the wrong ones and now have to wait for the rest to come).
2. No visible signs of cap failure (no bulging, expansion, etc) - no burn marks, but it does appear the caps have been replaced at some point.
3. Checking power leakage: I have a Fluke 110 and a Fluke 324 but sadly, no other test equipment.
As I observe the issues this keyboard is having, I can't help but be frustrated with my lack of knowledge of how it works. Can someone give me a brief process "map" of how this digital keyboard works?
Here is what I know so far (of course, correct me where I'm mistaken): It gets AC power and the power board transforms it into DC, sending it to the other PCB's.
Where I get fuzzy is which board does what, and in what order.
I'm guessing the Main Board is what processes the signals from the synth and keys and sends it to the "amp" board to provide the speakers & line out with usable signals.
When I turn on the keyboard, the 4-digit LED display tries to begin it's bootup sequence ("FP-8") but only gets to the point of flashing the letter "F" before failing. If I lean down toward one of the speakers, I can hear a slight hum. This tells me the "amp" board is getting SOMEthing, and therefore the issue must be earlier in the "assembly" line.
The board with the LCD display must not be getting adequate power as it does not light up. Is this a problem with that board, or another board?