exxos's Atari, Amiga & retro forum

Hi All,

I've just soldered up the 4mb exxos ram board and the Mega switches on just to a plain grey screen.
Quick flash from the floppy light and the reset circuit seems to work ok.

I've checked how I soldered up the shifter board board and I think the problem is there. I've soldered the socket where the pins should be and vice versa. Does this matter, ie are they pin for pin or do I need to swap them over?

Did you follow the assembly guide on my main site ?

http://www.exxosforum.co.uk/atari/last/4MBMMU/index.htm

Also assume you inserted the RAM board correct orientation ?

Yes but still managed to get the two sets of pins mixed up. The Ram board is fine, cable exits to the right. Shifter board cable exits to the back, opposite to STFM shown in the instructions. I just mixed the pins up on the shifter board, so that the header pins that go to the motherboard are nearest the white socket and not the socket.

If I remember rightly the shifter board is pin to pin.. It was just a breakout board.. I've been trying to find the PCB layout to doublecheck, but I have that many PCBs all over the place and I have no idea the file is called

Ok, cool, so hopefully I won't need to resolder it
Just find where another loose connection is.....

It won't boot to my dig cart either.

Was this the machine use having corrosion problems with ? Is possible there may be some other issues somewhere and besides the RAM ? Also assume you removed all the old RAM as well ?

Yes it was. I'm starting to think that the 2mb ram may have been keeping it working, lol but now its been removed.

Will have to get the scope out again i think.

There is a solder jumper on the board to force 1MB.. I think you said it was working but only 2MB before.. So maybe worth a try ?

Good point, will try that tomorrow.

I take it U58 and U59 now don't do a lot either? Is it safe to remove the caps from the old ram too btw?

I would leave the caps in, won't do any harm..

I think the chips can be removed.. You would have to double check on the diagram that they are only used for RAM signals.