1040 STFM and Exxos memory upgrade (1/4mb)

[DoG]

The cap seems to be soldered wrong? Shouldn't it go to the L51 side on the + on the cap? Or is this already "fixed"?

[wietze]

The cap is soldered wrong? The side that the arrow points to with the minus symbol on it is connected to the left pad, adn the other side to the right; is this wrong?

[exxos]

Just remove the cap, its not going to be doing anything on long wires anyway..

[wietze]

Which caps should I replace on STFM for the reset circuit? I cant seem to find the C100 and C102 as depicted on the pic on the post you made.

[exxos]

Looks like C2 and C7.

Capture.JPG

Though you may not have a reset issue as your getting bombs anyway. There are a lot of fixes for these machines which cause no end of problems, though I assume you have a bad connection on the RAM somewhere.

[wietze]

I guess the only thing that can be badly connected is how the memory module is fitted in the sockets then; by logical deduction (since yaart gives 1mb and no errors with socketed simms).

I will measure them as soon as I can.

[wietze]

Ok, I got closure on this topic :). I ordered another 1/4mb memory expansion and put that in; and it worked! So it was the memory expansion that was at fault. I must have borked it somewhere during the installation the first time!

[rubber_jonnie]

Since the original was not working and you suggested it was handled roughly at one point, it may be worth going over it and reflowing the headers. If you have a cold joint on one of them, it may not be visible, but could still cause you problems.