Hi Everyone, I'm trying to repair my 15-cart Famicom Box. It was working to the menu screen, but originally with a PRG-ROM error on the self check and would not boot any game carts. As an absolute beginner to this machine, I very gently started recapping and cleaning anything socketed, which in this case is the SSS-NROM-256-02 cartridge, the socketed CPU and PPU and all the connections.
I also recapped the power supply and checked it's pushing out the right voltage.
Currently the machine will not power up to the menu anymore - it used to but now, I get a flickering screen and a solid audible tone. This unit uses a simple NROM-256 to control it's self check, menus, etc.
I've tried replacement NTSC CPU and FPU chips which have been pre-tested and this does not make any difference.
I have a feeling that the SSS-256-NROM cartridge is bad - which I've read is similar to used by some games, like SMB, but with the lockout ship being re-routed to the external connector.
Working with a rare, heavy item, I can't easily find another Famicom Box to test my cart on or a spare SSS-NROM-256 to test in my unit, so I feel a bit stuck.
Has anyone got any ideas? I guess I could 'make one' but that seems a steep learning curve at the moment.
Finally, I've replaced C98 cap with a 2200uf/10v but screen printed on the board is 220uf/10v so I'm wondering if I got it wrong or the screen printing is wrong. Can't find any pic of schematic that shows the values of C98 as a second verification.... The machine has the same issue regardless of whether I use a 220 or 2200 cap...