More SNES mainboard repair!

Try eucalyptus oil

 

I guess we are down under aren't we! Might catch a koala while I'm at it to feed to the pet dingo? :biggrin-new:

Keep us posted on the progress, here's hoping it's a nice simple fix!

 

What I meant is that the chip address lines will be in parallel (not data) so U4's A0 will connect to U5's A0, A1 to A1 and on and on... If all test OK then make sure each address line has continuity with some PPU pin (the driver).

The data looks like it's all there so I wouldn't waste time with the data lines yet.

 

LOL, it surprisingly works really well. When I was making the Power Girl XBOX, many tutorials mentioned to use Oven Cleaner. That stuff is nasty, and yet Koala food works well! Didgeridoo dingo.

 

Just looked at the schematic, the chips are being used for top 8 and bottom 8 bits of a 16 bit bus, so yes the data lines are indeed not connected to each other on the vram.

(I am of course not saying this because you dont know it, just correcting my previous assumptions)

I did say it was without looking though

 

Just tested this now, the only A legs that were connected between each of the VRAMs were A14. A bad sign?

 

fireaza, where do you find these half-working SNES? do you get them like this or are they fully dead and after some repair this is what state they end up in?

SNES I come across in Australia are either working fine, or have been sitting neglected in shed conditions for 10+ years and are in need of major repair (recap, clean the slot, the case, basically not worth the time).

 

This is how a receive them, and yes I buy them with full knowledge that they're not working. It's just sometimes the solution to the issue is more complex than cleaning the cart slot or replacing the fuse

 

Ah, my mistake, the PPU1 drives each one independently--I thought they were arranged together as a 16-bit memory. So to test you need to find a PPU1 pin for each address line separately.

 

PPU1 controls BOTH VRAMs? Okay, I'll give that a shot!

 

Okay, I've checked all the A legs on both VRAMs. I got continuity from all of them to PPU1. What now?

 

Reflowing the solder pads, checking the rest of the signals, checking signals between PPU1 and PPU2, I suppose. Really it looks like an address line issue.

 

I'll try re-flowing the solder pads on the VRAM chips and PPU1. Rest of the signals being the other, non-A legs on the VRAMs? Where are they linked to?

 

Okay, I've re-flowed the solder on those 4 chips. I think the problem has improved, as when I popped in Super Ghouls and Ghosts, you can see uncorrupted sprites for a few elements:


While I was re-flowing the solder, I think I found what looks like corrosion. It's on the corner of U2, kinda behind and around the legs of the chip. It's too small to photograph though, so all I can do is describe it. The board in this area looks "different" from the board under U3, so that's why I'm suspicious.

 

Where did this end up? did you fix it or give up ?