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

Posted: 07 Feb 2020 17:44
by 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"?

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

Posted: 07 Feb 2020 19:11
by 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?

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

Posted: 07 Feb 2020 19:12
by exxos
Just remove the cap, its not going to be doing anything on long wires anyway..

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

Posted: 07 Feb 2020 19:24
by 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.

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

Posted: 07 Feb 2020 19:33
by 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.

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

Posted: 07 Feb 2020 20:01
by 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.

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

Posted: 16 Mar 2020 08:16
by 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!

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

Posted: 16 Mar 2020 09:36
by 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.