Sharp Twin Famicom Disk System Issue

[daskrabs]

I have a Turbo Twin (AN-505-BK) that I bought busted and dirty, but in decent cosmetic shape. New 3rd party PSU. The Japanese seller said "when power go in, smoke come out." I figured it had a bad main cap, correctly, which I replaced. The cartridge side now works fine, although the A and B buttons don't work, but they're probably just dirty contacts. The Disk System, on the other hand, won't light up at all. All I get is a grey screen instead of the "Set Disk Card" or whatever. No disk activity at all. Seems to be attached correctly and all. Any thoughts?

[SegaSonic9]

It may be busted or have a bad power board.  You can replace FDS drives in a Twin with a regular FDS system.  If it is a power issue though, that will not work.  I do not remember if there is a fuse on the FDS side, have you checked for that?

[daskrabs]

So a Nintendo FDS drive is a drop-in replacement for a Sharp one?

[2A03]

So a Nintendo FDS drive is a drop-in replacement for a Sharp one?

They're the exact same drive so yes.

[SegaSonic9]

Ummm, silly question, but are you moving the switch to "disk" when you try to use the FDS?  It will display a grey screen unless the system is switched to disk mode.

[daskrabs]

Yes I flipped it

[SegaSonic9]

Heh, sorry, I said it was a stupid question   Did you check for a fuse on the FDS side?

[daskrabs]

Yeah, there's no fuse.

[Sydsydsyd]

Today I was trying to play with disk mode and I don't have the classic image of Mario and Luigi jumping anymore, I get a gray screen.

Some time ago I closed the pins of the socket because it was very loose and I think that the pins that are facing each other were short-circuiting when there is no cassette placed in the socket.

I think this may have burned a chip on the floppy side of the motherboard. If that were the case, which part of the PCB (which chips) should I check? Is there some kind of fuse or logic gate that could blow due to what you mention? Thank you very much.

I hope this will help to the entire community to solve this problem, cuz I was searching a lot on the internet and couldn't find anyone mentioning that this could be the cause of this grey screen issue on disk mode.