+5vdc running unnecessarily high is a common overlooked issue for early Bally games. On all the bally driver boards there is an 100 ohm resistor across two legs of the regulator. If you cut this resistor out, the voltage will drop down a quarter volt or so, sometimes more.
Every voltage regulator is a little bit different and most do not need this resistor. If your bally driver board runs over 5.25vdc, I would cut out R49.
Here is an extreme example. First pic, R49 in, 2nd pic R49 lifted.
I do not know how the PSU5 replacement regulator handles this resistor. Anyone that has used them please chime in.
I really think a lot of MPU u15 failures could be avoided if the +5vdc ran closer to +5v. I just have anecdotal evidence at this point.
Actually, I wasn't even thinking of the PSU5 replacement...but that does bring up another thing to check.
I was curious if there was a difference between an original LM323K and one that was new(er).
Quoted from ForceFlow:Actually, I wasn't even thinking of the PSU5 replacement...but that does bring up another thing to check.
I was curious if there was a difference between an original LM323K and one that was new(er).
When i use brand new LM323Ks it seems they still vary output voltage somewhat. They are more consistently closer to 5v usually than the ancient ones, not sure if that is because of how the regulator was manufactured or if the regulator just drifted voltage over a long period of time.
Quoted from RCA1:Seriously, where's the easiest point to test this with a DMM? One of the test points to ground?
TP1 or TP3. In fact, there is a reliability mod you should do by adding a jumper wire between TP1 and TP3 (except NOT for Baby Pacman)
Quoted from RCA1:You just want to show off your cool new mini display gizmo again!
more details on this mini display gizmo please
Pinball ninja's idea. I don't want to steal his thunder. Subscribe and check it out.
I mount mine differently than the ninja tho for the sdb. I pickup the gnd and +5v at the 0.1uf bypass cap right near the dvm block. I drill a hole for the wires.
Quoted from Whysnow:more details on this mini display gizmo please
He's referring to the little digital voltmeter display mounted to the SDB (see blurry 
pictures above).
Quoted from barakandl:Subscribe and check it out.
I am a subscriver but stopped regularly checking out the site a while ago when there was no more regular updates. I guess it is time to check back in. I love teh ninja site!
Quoted from wayout440:TP1 or TP3. In fact, there is a reliability mod you should do by adding a jumper wire between TP1 and TP3 (except NOT for Baby Pacman)
is that baby pacman solenoid board and why is that
Quoted from rockhouse:is that baby pacman solenoid board and why is that
The driver board in baby pac is completely different (has lamp driver SCRs on it) and they must not use the same TP labels.
To answer question in post #4 -- The PSU5 regulator expects pin 3 (case) to be at ground potential so for those, it is best to remove and replace R50 with a wire (or solder a shorting wire on back). For the PSU5 regulator - R49 does nothing other than add another 50mA load to the regulator.
Quoted from barakandl:The driver board in baby pac is completely different (has lamp driver SCRs on it) and they must not use the same TP labels.
Then it probably also applies to goldball as well. It uses the combo lamp/solenoid driver board as well
Quoted from r6emperor:Then it probably also applies to goldball as well. It uses the combo lamp/solenoid driver board as well
Goldball and Grand Slam use a combo driver board, but it's a different board. Those two games use an AS-2518-147. Baby Pacman and Gators use an AS-2518-107. Since I haven't had occasion to look too closely at a Goldball, I'm not sure what the actual differences are between the two combo driver boards.
Quoted from barakandl:The driver board in baby pac is completely different (has lamp driver SCRs on it) and they must not use the same TP labels.
This is correct, on Baby Pac, TP1 is 13-16V unregulated and TP3 is logic ground! Tying them together wouldn't be good!
Quoted from Schwaggs:This is correct, on Baby Pac, TP1 is 13-16V unregulated and TP3 is logic ground! Tying them together wouldn't be good!
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