DX7 Choke Coils

[between3and20]

I bought a DX7 with weird power issues with, what I was told, were typical problems (weird symbols on display, patches sometimes don't work, etc).

I narrowed the issue down to the first power board. Where there should be two choke coils, someone replaced with capacitors. It apparently worked for a while, but I'm just confused.

The choke coils that should be there are referred in the manual as SN8S-309 coils. I did some digging to find Yamaha used GE 900490 coils for this part.

I guess my problem is I can't find any equivalent/replacement part for this and neither could the last person that worked on it. Any known/potential solutions to this? Or would it just be easiest to bite the bullet and buy another psu board.

[SciNote]

I am not a technician, so if I opened up something like a DX-7, I'd likely not be able to tell what is wrong with it unless there was an obvious, physically damaged component. But I know something about electronics -- I was a professional car stereo installer, I've built many electronic (albeit relatively simple) modifications for my car, I know how to use a multi-meter, and I am familiar with Ohm's Law. And what surprises me here is that you said that someone replaced coils with capacitors, because in my experience, these components are essentially opposites. For example, when building speaker crossovers, coils are used like low pass filters, to block high frequencies and let lows pass through. Whereas capacitors are used as high pass filters, to block bass (and in fact, for this application, they are often called "bass blockers") and let high frequencies through. So I am surprised that one could be replaced with another and that the original device would still work as intended. But again, I am not a technician, so maybe there is some way that this is possible.

[crochambeau]

Yeah, inductors will pass DC whereas caps will not (unless they are electrolytics installed backwards, resulting in breakdown). So these parts being confused in a power supply is problematic.

Do you mean being replaced with resistors?

Are you able to share pictures of it?