anyone have power supply details on F2 processor board?

[rkahr]

Hi all,


I've picked up a Fortune II draw power and it isn't booting.  I've pulled the processor board and have been performing some tests - but some of what I'm doing is blind because (1) I don't have a schematic and (2) this is a 4-layer PCB which makes it difficult/impossible to follow traces to ascertain the circuitry.


I'm pretty confident I've got a power supply issue because I'm only seeing 1.25v across the ground and supply pins on the discrete logic chips on the board. 


I'm including a picture of the power supply portion of the board; has anyone seen a schematic of this section of the circuit?


Things that concern me in this picture: 


1. the two diodes soldered together in a single component's position just below the LN3302 comparator.  This can't be factory, can it?
2. just to the right of the same comparator is a resistor that appears to have questionable solder joints
3. a good portion of this area on the board has discoloration that I associate with excessive heat.


Things that seem promising from testing in this area:


1. The three large caps hold a solid 9v DC. It looks to me like they supply the LM338


Anyway, thoughts/tips/tricks/advise/clarifying questions welcomed!

I couldn't get the attachment feature work, so here is a link to the JPG on my pinball parts website: http://www.kahr.us/image/F2_MPU_PS.JPG

-Rob

[Paul]

A good place to start is replacing all caps as a high esr can bring down your power rail.

[Badbaud]

Hi all,


I've picked up a Fortune II draw power and it isn't booting.  I've pulled the processor board and have been performing some tests - but some of what I'm doing is blind because (1) I don't have a schematic and (2) this is a 4-layer PCB which makes it difficult/impossible to follow traces to ascertain the circuitry.


I'm pretty confident I've got a power supply issue because I'm only seeing 1.25v across the ground and supply pins on the discrete logic chips on the board. 


I'm including a picture of the power supply portion of the board; has anyone seen a schematic of this section of the circuit?


Things that concern me in this picture: 


1. the two diodes soldered together in a single component's position just below the LN3302 comparator.  This can't be factory, can it?
2. just to the right of the same comparator is a resistor that appears to have questionable solder joints
3. a good portion of this area on the board has discoloration that I associate with excessive heat.


Things that seem promising from testing in this area:


1. The three large caps hold a solid 9v DC. It looks to me like they supply the LM338


Anyway, thoughts/tips/tricks/advise/clarifying questions welcomed!

I couldn't get the attachment feature work, so here is a link to the JPG on my pinball parts website: http://www.kahr.us/image/F2_MPU_PS.JPG

-Rob

Email me at aldor@coam.net and I can send you the schematics for your board.
The files are way to large for NLG. They are scans of scans but readable.
Usually the diodes get so hot they break a trace on the back of the board, caps have never been an issue, I have repaired many of the F2 boards, have a tester and parts to get them running.

I don't think it is a 4 layer board.

Alan AKA badbaud

[rkahr]

Badbaud you ROCK!  And you're right, it's not the caps.  I stumbled across the regulator's nuts being loose; tighten those down and the supply runs at 4.85v.  Plenty more to work through on this board so the schematic will be a huge help - thanks 1x10^6


-Rob