Your rectifier board ( TA 100 ) test points look OK except TP2 – should be about 230 VDC. But the strange thing is TP4 on the SDU is showing 261 VDC. They should be the same – same circuit. However this would not keep it from booting ( the 230 VDC is for the displays).

The SDU is showing 16 VDC at TP5, which is good (should be about 12 VDC) and that is what is driving the 5 volt section. But you only show 45 MVDC at TP1 and TP3 (should be about 5 VDC). You need the 5 VDC to power the MPU for booting. I think this is where the problem is.

Could be C23, C24, C25 or the 5 volt regulator.

Bob

Looks like those resistors got toasted and should be replaced, but that's the high voltage section and wouldn't keep it from booting. The high voltage is for the displays.

If it was me I'd pull the board and replace the capacitors in the 5 volt section, replace the toasted resistors, and the 2 caps next to them and the C26 cap in the high voltage section - While your there I'd also replace the header pins and make all the ground mod's.

It would be good for several more years.

Bob

Also check the traces around those toasted resistors.

The voltages on the rectifier board look good except TP2. Re-check the voltage there - should be about 230 VDC. You show only .8 VDC. But the strange part is the voltage at the SDU shows 261 VDC. This don't seem right. It's the same circuit. How can it be low at the rectifier board then back up at the SDU?

Bob

http://www.pinwiki.com/wiki/index.php?title=Bally/Stern#Solenoid_Driver_Upgrades

Then how do you know you're not changing bad parts with more bad parts. Follow the schematic with a volt meter. First check L1.

Bob

Sorry Blake, my bad - I should have said check L2. 5 volts comes in at J4 pin 16 and 17 then to L2. Check both sides of L2 for 5 volts.

Bob

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Are you testing in the machine or on the bench with a power supply?

Using your DMM check continuity - connect to J4 - 16 or 17 then check these places. Should show as short.

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Pull off one side of L2 then check for 5 volts.

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