We still need to know if the drivers are driving back to the rail.
Do you have two scope probes?
Do you have two scope probes?
Use 2 channels.
Touch both the the negative rail to make sure that they both deflect to exactly the same point. Then move one probe to the gate.
If you have a 0.1uf cap, solder it between the gate and source and repeat this.
Post the scope display(s).
Touch both the the negative rail to make sure that they both deflect to exactly the same point. Then move one probe to the gate.
If you have a 0.1uf cap, solder it between the gate and source and repeat this.
Post the scope display(s).
Yes. Just post the one without the cap.
The cap value really isn't important. It's just to load the drive circuit.
The cap value really isn't important. It's just to load the drive circuit.
seems like the drive is falling just short of the rail:
scope settings
An externally hosted image should be here but it was not working when we last tested it.
scope settings
An externally hosted image should be here but it was not working when we last tested it.
I can't see it well enough to tell what's happening. Why doesn't it have a drive signal like it did before?
That's FAR too much. not critical means it doesn't have to be exact.
Just post the signal without a load.
Just post the signal without a load.
drive
drive and rail
An externally hosted image should be here but it was not working when we last tested it.
drive and rail
An externally hosted image should be here but it was not working when we last tested it.
What's the resistance from base to collector of Q9. Measure, then reverse the probes and measure again.
You can't measure resistance if the circuit has voltage on it. Do this after the capacitors have discharged.
I don't think you ever posted a photo of the driver board end to end. Are the 4 driver transistors you've shown the only 4 on that board or do they have another 4 on the other end as well?
If necessary, could you remove the 4 driver transistors without removing the driver board?
If necessary, could you remove the 4 driver transistors without removing the driver board?
