Digital Designs Z2HV

[Perry Babin]

You have to check at all points from the output of the IC, the base of the drivers, the emitters of the drivers and finally at the gates of the FETs, preferably with a loading capacitor).

 

[caraudioguy2100]

I replaced the drivers for the banks of fets that were heating up .

here is what I get now do I still have an issue or do these look ok ?

I’m using a 0.1 if cap between gate and source

scope set to 2us 5 volts/div
The reference line was centered before taking the pic

 

[Perry Babin]

The amplitude looks higher than I'd expect (could be due to scope calibration) but the shape of the waveform looks OK.

 

[caraudioguy2100]

Replaced the drivers in the bank that was giving me heating issues .

That bank of fets still get hot after 10 secs

here is what I get on the gate leg for the fets scope set to 5us 2volts div

I installed a different power supply driverboard without the 3 pin header could this cause the issues I’m having or any ideas ?

 

[Perry Babin]

Measure the frequency with a multimeter on pin 9 or 10 of the 494.

Post a photo of the waveform on either of those pins (they should be the same).

 

[caraudioguy2100]

I removed the fets out of that bank for now so I don’t damage them .

before taking the measurements you requested do I need to load that bank with a cap ?

 

[Perry Babin]

It shouldn't make a difference back at the 494.

 

[caraudioguy2100]

Here are pics of pins 9,10 scope set to 5 us 5volts div

I got a reading of about 25k for the frequency

 

[Perry Babin]

That looks OK. Do you have 12v on the collectors of all of the NPN driver transistors?

 

[caraudioguy2100]

Yes

 

[Perry Babin]

Signal on base and emitter of the driver transistors?

 

[caraudioguy2100]

So post the waveforms on the base and emitter of the npn driver transistors ?

 

[Perry Babin]

Yes

 

[caraudioguy2100]

This is still with the fets removed out of that bank .

here is base and emitter all npn drivers look identical

 

[Perry Babin]

Lead the FET locations with a capacitor and repost these.

 

[caraudioguy2100]

Load all fet locations in that bank or just 1

 

[Perry Babin]

Just 1 for now.

 

[caraudioguy2100]

Scope set to 5us 5 volts Div

 

[Perry Babin]

Are you sure that you didn't have a defective FET, in post 44?

Did all FETs have the same waveform that you posted, in post 44?

 

[caraudioguy2100]

I tested all the fets and they tested fine . And all fets had the same waveform .

Not sure if one is defective or not even tho they check fine