Space Duel 5V halves

[Zinfer]

Finished pulling socketed IC's and roms. Checked for any changes in ohms between +5 and grd after each pull. checked for visible shorts or bad traces under the socketed IC's. Nothing found. I did run a heat check and found the only component that gets hot is VR2's 7815 voltage regulator but that regulates the +15v.

 

[Zinfer]

There was a substantial jump in ohms from .890 to like 1.5 after I pulled Prom @P7

 

[Zinfer]

Ok, well hrm. Double check me on this. I think perhaps I've found the problem. I'm running an AR2 voltage regulator that is a A035435. Upper left of the board edge is stamped 0660786 and then written in sharpy -02. I was told this came out of a Space Duel. However doesn't a Space duel use a -04?

 

[ELutz]

Ok, well hrm. Double check me on this. I think perhaps I've found the problem. I'm running an AR2 voltage regulator that is a A035435. Upper left of the board edge is stamped 0660786 and then written in sharpy -02. I was told this came out of a Space Duel. However doesn't a Space duel use a -04?

Yes, Space Duel uses a -04.....but.....you can use a 02 in place of a 04.....but not the other way around.

Edward

 

[Zinfer]

Not getting anywhere with this board. Everything LOOKS good. Those are the worst.

 

[Zinfer]

Well then again-
After fiddling all day with the pcb and not finding anything obvious, I happened to move the ARII board a bit and power started increasing from 2.0 all the way up to 3.85. I isolated what I feel is the issue at Q2. I managed to get the voltage up to 4.85 by putting direct pressure on Q2.
'm thinking the correct replacement for it is this:
http://www.newark.com/fairchild-sem...2427?matchedProduct=tip32&whydiditmatch=rel_1
I'm fairly certain this is my +5v issue. If this is so, I haven't even gotten to pcb repair yet as I'm probably going to need right at 5 or slightly above just to get it fired up. While I'm at it I should probably pick up an ARII rebuild kit.

 

[Zinfer]

Yay! I fixed the problem with Space Duel halving the voltage AND found the short. I replaced Q2 as part of an ARII rebuild kit. That got my +5v back. I also am just a little sheepish to say I must have had a newb moment somewhere along the line. I found the Eprom at J1 was actually in socket backwards. Doh!
Wondering if I should start a new thread at this point. The board appears to be dead. I have not replaced the AVG yet as I had to return it for a broke pin. I checked the +5 -5 and +10 voltages at the onboard taps and they all check out fine.
Where do you start with a dead board? The only part that is live is the Red LED is lit. Heat check - everything pretty cold. Of course the spot killer is lit on the monitor as well.