Twin Famicom video issuue

[Fresh]

Hi,

I apologize if there are any threads or resources addressing this. I've done some searching these last few days, but as I am really quite lost I figured the safest bet would be to ask about this first.

I've had a Twin Famicom for some months now, it hasn't had an issue. After playing for a while the other day, the game's graphics became garbled so I turned it off, and didn't think anything of it. I figured it was just a glitch.

At this time, when I boot it switched for disk system play, the screen looks like this:



And when I try to load a famicom cart, it looks like this:


(though this was 'playable')

At this time the console will not read famicom disks, I tried the game that I was playing when it corrupted and another to verify. However, due to all of the garbage on the screen, I can not read the error code. I'll deal with that when the time comes, but I figured I would mention it in case it is pertinent to the overall issue.

Anyways, rather than jumping to my own conclusions I felt it would be best to ask about this. If this is a hardware fault or something I've done, I just need to know . Thanks folks.

[133MHz]

If the game runs OK even though the graphics are garbage, your problem lies in the CHR / PPU data bus, which is usually caused by dirty contacts on the games or cartridge slot. If it even fails on disk mode then it becomes quite a bit more serious. It could be caused by cold solder joints, faulty VRAM, faulty address latch or even a bad PPU.

First try to rule out the simpler causes by taking the motherboard out, giving it a good clean and checking it for cold solder joints. Check the PPU traces to/from the cartridge slot with a multimeter, especially PPU D0 to D7. Otherwise start looking at the 2K VRAM, the LS373 and the 2C02 as possible suspects.

[ericj]

Good suggestions, 133MHz.

I had a similar thing happen with one of my FDS copiers awhile back. Turns out it was a faulty, cheap AC adapter that wasn't putting out enough amperage. Although the problem here is different, it may be worth testing it with a different AC adapter first.

[Drakon]

Oh man that could be a whole number of things.  Does it work okay with carts?

[Fresh]

Nah, the carts will load but they are garbled.

Thanks for the suggestions guys, it gives me a good place to start.

EDIT:

I've started cleaning and it has helped a little bit. Enough that I can see some of the screen now, but it fluctuates. The error code is semi visible now though and I'm thinking it's reading error code 20.

[Drakon]

literally that could be a loose connection on any number of chips.

[Fresh]

Looks like it was, yeah. After checking the connections everything seems to be in working order now, and the disks will boot too. Cheers folks, thanks .

[Drakon]

Glad you got it working.  My first twin famicom arrived today and I'm really enjoying this system.  I already threw rgb and s-video into it....I'm still working on some stuff before I'll post the work