High Speed
Williams, 19861986 sys 11 High Speed : 5 volts is 12.5v
The game wouldn't come up, felt lots of heat on the sound ROMs and checked 5 volts = reading 12.5v
Replaced the caps on power supply with a 8 electrolytic cap kit, still getting the same voltage.
Took voltage readings at the wires that run to the 2N6059 transistor
B 13.5
E 12.5
C 14.6
Any suggestions ?
Well, first of all, your main board is gonna be fried. If 12v went to your 5v chips, they probably are toast. Have you replaced your bridge?
I put a bridge in temp before I swapped caps, same voltages , so I put original back in - also I swapped the 2N6059 and got same voltage so I put the original one back, before doing the cap kit.
I was thinking that the rest of the boards that use 5 volts will be messed up too after feeling the heat off the eproms. Hoping for some luck on that once the power supply is back at 5 volts.
At this point, there isn't much left you haven't replaced. I'd measure the diodes on the power supply to make sure they're okay, and then replace the IC.
Quoted from oneperson:Took voltage readings at the wires that run to the 2N6059 transistor
B 13.5
This is your problem, should be @ 6.5 volts. So the regulator chip is not applying any control voltage to Q-5. With no control Q-5 will pass unreg voltage straight thru - a pn junction drop.
Got a voltage IC , NTE923D and installed it = much closer to 5 volts now, Thanks CadillacMusic !
So the voltage I read at the base was not from the IC, but passing through the Transistor - Thanks GRUMPY !
The 5 volts is a bit low 4.86
I did not get lucky, as far as the other boards that use 5 volts are concerned : Looks like they are damaged from the over voltage 
pinballplusMN . Too bad when the power supply fails it is able to pump higher voltage through the 5 volt system like this.
Quoted from oneperson:The 5 volts is a bit low 4.86
If you change R-8 to 5.11 k ohm this will rise to 4.96 volts. If you change it to 5.23 k ohm your output will be 5.05 volts. Be sure to only use 1% resistors.
I just had a Pinbot that had the same issue. All of the eeproms were bad. Alot depends on if the game was on for a long period of time under this over voltage condition. You may want to replace your eeproms first and see if the boards come up. You may get lucky.
Looks like I got kinda Lucky after all (once I dug up a eprom burner that would halfway work with a PC to copy BIN files from web) replaced all but one of the eproms and the system is back up, even sporting a "0"! Thanks for the tip pinballplusMN
Also got the 5 volts looking much better, under load, with the resister trick, thanks for that info GRUMPY
Sorry to revive an old thread, but having similar issues with my High Speed. Power Supplied failed and supplied 12 volts to the +5 volts line (regulator chip failed). I replaced 3 Eproms and when I test on the bench the LED is showing "8". Not sure where to go next and would gladly take any help.
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Ashley, IL
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