Transistors are like a switch. Think of it this way. You have three legs. One is input, one is output, and the third one is the switch. If you apply a small amount of voltage to the switch leg, you turn on the transistor connecting the input and output together and allowing current to pass through.

You should test the transistor before replacing them. All three can be easily tested with a DMM. Save you time and money. The one in the to-3 case is expensive. Look up testing transistors with a DMM on youtube.

If the resistors are bad, they are usually burnt looking. The resistors are often bad in the high voltage section. R51, r54, and R55 burn the most often if I am remember correctly.

Find zener diode VR1. With the power on, carefully check the voltage on the banded side of the diode. You should see +140vdc there. If it is low replace VR1 (this is after replacing / assuming resistors are all good and in spec).

Andrew

The pins in your picture that you have highlighted are ground return pins and solder can be touching / continuity. They honestly look okay from that side of the board. The final bottom pin CAN NOT be touching. That is a 5v pin and will blow fuse if it shorts to ground.

That is a connector i find almost mandatory to replace. It caries all the power for the logic boards and needs to be good shape with no resistance.

Funny thing...

I just repaired a Driver board tonight with the same symptoms as you after rebuilding the resistors/filter cap. Low output voltage (100v), yet i could adjust it with the pot, just not high enough. It was the zener diode.

The one used on the bally board is rated for 1/2w. You can use a 1w version just fine. It has a different part number i can not recall off the top of my head. Maybe your supplier has that version. You can test this zener diode, but you need to lift one leg to do so in this circuit.

Ed at Great Plains Electronics i'm sure sells this component.