exxos's Atari, Amiga & retro forum

I recently got a working C103253 REV 3 - C103088 REV 5 (SMT RAM) STFM board with 512KB. I also got a new 4MB MMU TYPE RAM upgrade from the Exxos store with the preassembled shifter adapter.

I installed it today and am getting a white border with black and white vertical bars.

I lifted R59, R60, and R61 on the gold side and connected to the positive side of the large resistor.

Notice that pin 1 of the MMU faces right on this board revision.

Am I missing something?

What you have is certainly a RAM issue, that sort of screen is a dead giveaway.

My suspicion is that the MMU component isn't inserted far enough into the socket and isn't making good contact. It needs to be inserted really quite far, and if it's not in far enough, or uneven, then you may hit problems like this.

If you had to assemble the Shifter adapter yourself, double check for shorts and double check the cable is inserted the right way up. You may laugh at the last one, but I've seen it happen.

You should also check there are no legs bent on the Shifter IC, that the IC is correctly oriented (i.e. the notch denoting pin 1 is in the correct spot) and that there are no legs bent or snapped off on the bottom of the Shifter adapter where it plugs into the mainboard.

If you had to fit a socket to install the shifter adapter, then check the soldering is good. Also, it's possible you've lifted the 3 resistors at the wrong end, you need to be feeding 5v through them to the RAM. IIRC on these boards you need to lift the other end of the resistors. Double check which end of the resistors go to the RAM and adjust if necessary.

I'd also advise to use a normal wire rather than a breadboard jumper wire and using something to ensure the ends are insulated.

That's about it.

Thanks for your help.

I pushed the MMU component as far as it will go into the socket.

I got the shifter adapter preassembled, so hopefully, that's not the issue.

The ribbon cable has the blue lettering on top on both ends, so it should be good.

It looks like the shifter IC is oriented correctly and no legs are broken or bent.

Luckily my shifter was already socketed, so I did not have to install a socket.

I'm not sure about the 3 resistors. It looks like the side of the resistors with the golden stripe is the one that needs to be lifted. Also, there is another resistor in the same grouping that I don't know if it needs to be pulled (this is a weird board revision!). I cannot see the number because it's under the big capacitor, but it could be the R146, that I see on a Revision 1 image.

Pretty sure it's the wrong side of the resistors you've tied to 5v.

I'd start by looking there and switching them around.

Pretty sure it's just those three.

rubber_jonnie wrote: 30 Jul 2023 20:49 Pretty sure it's the wrong side of the resistors you've tied to 5v.

I'd start by looking there and switching them around.

Pretty sure it's just those three.

Yup. It should be the end nearest the MMU-chip. R60-R61 is enough.

The issue was with the resistors. I had pulled the wrong side. It boots now!

Thanks a million!

:girldance: :girldance: :girldance: