texasmame
Well-known member
So, have a Stargate that had some issues and got past those until I got to the CMOS. Turns out the CMOS was shot (5514). Swapped in a 2114 and it works normally now but it doesn't save scores correctly.
There are NO volts at pin 18 when the batteries are in, so somewhere along the line, it's dropping. When powered up, pin 18 gets just under 5v.
From the schematics, it looks to my novice eye like the 4.5 from the batteries goes through D10, then C3 and right in to pin 18 of the CMOS but I'm sure I'm missing something here.
First, I went directly from the 4.5v on the battery holder to the 18pin. It would scramble scores/settings when turned off. Remove the 4.5v and reboot - all better.
Then, thinking it needed the D10 in there, I ran it from the end of the D10 where it was about 3.8v to pin 18 - same result. Then from C3 to pin 18 - same.
Then, after following some traces, I found that pin 18 of the CMOS tested good for continuity to pin 6 of 6I but pin 6 seems to not be represented on my drawings - some others for 6I are, but not pin 6.
So, at this point, I guess I could replace 6I as it seems to tie directly to 1C pin 18 and hope that's it as jumping 4.5v directly to the CMOS pin doesn't seem to cut it.
Suggestions?
There are NO volts at pin 18 when the batteries are in, so somewhere along the line, it's dropping. When powered up, pin 18 gets just under 5v.
From the schematics, it looks to my novice eye like the 4.5 from the batteries goes through D10, then C3 and right in to pin 18 of the CMOS but I'm sure I'm missing something here.
First, I went directly from the 4.5v on the battery holder to the 18pin. It would scramble scores/settings when turned off. Remove the 4.5v and reboot - all better.
Then, thinking it needed the D10 in there, I ran it from the end of the D10 where it was about 3.8v to pin 18 - same result. Then from C3 to pin 18 - same.
Then, after following some traces, I found that pin 18 of the CMOS tested good for continuity to pin 6 of 6I but pin 6 seems to not be represented on my drawings - some others for 6I are, but not pin 6.
So, at this point, I guess I could replace 6I as it seems to tie directly to 1C pin 18 and hope that's it as jumping 4.5v directly to the CMOS pin doesn't seem to cut it.
Suggestions?

