Williams High Speed Power Supply Delivering 12V at 5V Power Circuit...Gack!

Williams High Speed Power Supply Delivering 12V at 5V Power Circuit...Gack!
Let’s hope that the MPU and background sound boards were not damaged by the 12V when it should have been 5V.

[@stephanvoskamp1673]

Helped me fixing my High Speed II power supply. Measuring MC1723C at pin 4 and 5 I found the problem. Thanks for the tip. A capacitor for the 100V was blown. I don't need this as I have LED. The blown capacitor probably took out the MC1723C.

[@ChrisHiblerPinball]

Excellent. I’m happy that these videos are helping people.

[@paulwelka8288]

Thanks a million! My Space Shuttle power supply was delivering 12V on the 5V pins (and the machine wouldn’t boot). Sure enough the LM723 had failed. It must get hot residing next to the big honkin’ heat sink on the power supply board.

[@ChrisHiblerPinball]

I'm glad the video helped!

[@troxel7368]

Great tip with the connector housing. Why haven't I thought of that :).

[@ThePinballNoob]

I really hate to ask such a dumb question, but I am the pinball noob after all! Where do you put the black lead for this test? A ground? If so, does it need to be a particular ground or will any ground work?

[@ChrisHiblerPinball]

No biggie. Ground is Ground the World Around. That is, any backbox metal is a good ground point. Even the side rails of the game should be connected to ground.

[@ronnyverminck2741]

What causes the +12v drop to 9.5-10v when the MPU is connected?

[@ChrisHiblerPinball]

The difference between loaded and unloaded circuit.