Transistor Part Numbers for Q130-Q139 in a Kole PH2-3000D

[whitejohnny]

So what are the rails supposed to be?

[Perry Babin]

The out terminal is used as the reference for the drivers. The high-side drivers basically ride on that point and drive the high-side outputs on and off from that point.

Rail voltage of approximately ±70v would be about right. It's difficult to get negative 200 and only positive 68. They should be about even since they're taken from the same windings. Measure the voltage again on the center legs of the rectifiers. Do you read the same positive and negative voltages there?

[whitejohnny]

Ok, regarding the OUT terminal, excellent explanation - I was asking myself what should the gate voltage be, and then considered the example of an N type fet with pos rail on the drain and load at the source - if gate-source has to be ~ 2volts to turn it on, then as output changes the voltage at the source change, so you're trying to hit a moving target... And you don't need the reference for the low-side because with load at drain and neg rail at source you have a static target, right?

On this board there are 4 rectifiers and two transformers - I checked all 4 from each transformer's center tap. That was the result I got.

The KA3525 chip is the same as the SG3525 right?

I'll measure the voltages on the 3525 when I get a chance. R173 smoked again, then R190 after I removed all of the outputs.

[Perry Babin]

Do the symbols on the board match the symbols on the rectifiers?

[whitejohnny]

Yes, they match. All read about 380 in the proper direction and steady climb in the other (filter caps right?).

[Perry Babin]

The KA and SG ICs are the same.

Right. It's charging the filter caps.

If you shine a bright light from the back of the driver board and look at it from the other side (around Q124 and Q125), do you see any dark shadows that are not related to anything on either side of the board? Clean both sides of the board with acetone before doing this if the board is dirty.