Skar RP4500 waveforms

[bl4ckw1d0w]

I don't understand what this waveform in the attached photo is telling me.

It has a significant dip in the top before it pulls down. This bank is heating up with a 2ohm limiter but i do have the fets clamped similar to what you have recommended in the past with a binding clip and an old clamp from a kicker.

Its taken from the Gate of IRF3205 Q16A. It drives the transformer that has the additional winding for the 15V regulators.

The probe is grounded to the source leg.

Photo #2 shows the waveform I am seeing on the gate of the other banks driving different transformers.

 

[Perry Babin]

The pulse width is too wide. It may have driver issues.

 

[bl4ckw1d0w]

I suspected that. The originals were marked ZL. Quick search showed they were BL Galaxy Electric 2sb1260. I Have Rohm 2sb1260's marked BE that i tried HFe rank R. I will try HFe rank Q.

 

[Perry Babin]

Post the base signals of both drive sections from the waveforms you posted and the emitter waveform for the waveform on the left above.

These are on the driver transistors.

 

[bl4ckw1d0w]

Correct me if I am wrong but according to the datasheets the pinout is different from the originals?

 

[Perry Babin]

Both are BCE.

 

[bl4ckw1d0w]

From left to Right:

Emitter of Q8H
Base of Q8H

Emitter of Q8
Base of Q8

I will swap Q8 out.

 

[bl4ckw1d0w]

Changed it out waveform is fine now. Wierd. That was a brand new part.

 

[Perry Babin]

Running cool?

 

[bl4ckw1d0w]

I spoke to soon. I checked the waveforms on the transformer windings going to the rectifiers. The bank is still running hott i think. The transformer is putting out 75v AC. The other banks are 73 and 72v ac. I checked the other side and all transformers are outputting 72v ac. I dont trust my sense of touch im going to use a thermal image camera to confirm.

Should all the AC voltages combined at the rectifier be the same?

 

[Perry Babin]

Do you have one FET gate leg that's different?

Do you have one of the diodes that clamps spikes that's shorted or leaking?

Small differences like noise or ringing can cause a slight difference of voltage.

 

[bl4ckw1d0w]

Its running warm on one side.

 

[bl4ckw1d0w]

So i may be killing the drivers with a heat gun. The Q7A drivers of the bank next to the one i just replaced now look like the attached photo.

 

[Perry Babin]

Don't use hot air to install anything. I don't even use it to remove parts. The only good thing I found to use it for is to remove/install terminals block or other high-mass parts.

 

[bl4ckw1d0w]

Lesson learned all that time spent because i was too lazy to use soldering wick and an iron. I only used it for removal never had any regard for the surrounding parts. Definitely was the hot air gun i want to throw it in a bin and not touch it.

I am down to 1.2amps idle current from 1.8amps and power section running smooth.

I don't have the confidence yet so i like to have you walk me through things and go back and read up.

Thanks again Perry.