2 Monoblock Class Ds Not Working, I'm Lost

[D132]

I have a random assortment from various electronic part-outs

 

[Perry Babin]

Try a 1uF from the ground terminals on the driver board to remote and a 10uf from ground on the board to the 12vB+ terminal on the board.

Do those stop the 1/2 protect issue?

 

[D132]

Just confirming this is how I should solder them?

 

[Perry Babin]

That's right. Make sure the caps on the board are discharged and no power applied to the amp.

 

[stocktrader200]

There are 2 parts , power supply and amplifier.
If the power supply died it can be fixed easily
If the amp died, almost all silicon in a class d gets fried when it fails. Outputs shorted and driver chips shorted , the oscillator comparator may still work.
If it died bridged both channels may be dead.

 

[D132]

Power supply seems to have had a previous repair as there were some char marks on the heat sync and board around PS fets, not to mention 4 different batches and a shorted fet. I replaced all PS fets with new and same-batch fets. The amp powers on normally but seems to have an issue with the protection circuit. I believe the output fets are fine but I'm unsure about the driver chips as of right now, and I'm not sure how to check the oscillator comparator.

To Perry's message I will double check the caps are discharged and will update when I have soldered them.

 

[D132]

Are these alright for the capacitor ratings? Both are 50v rated

Also these are the connections to the board, aren’t pretty but they make good contact to the board and to ground (checked with multimeter) Looks alright or should I be aware of anything? Just want a second opinion

Wires are to connect to the capacitors as the cap legs are too short to reach

 

[Perry Babin]

The wires can make a huge difference.

The caps are likely OK. I don't trust that type of tester. 50v is plenty. They will only see battery voltage.

 

[D132]

A good difference or a bad difference?
Should I do it differently?

 

[Perry Babin]

A bad difference but it may not be enough to prevent them from helping.

If this doesn't help the problem, solder one leg directly to the board and use the shortest jumper (within reason) to make the second connection.

 

[D132]

Seems to have gotten rid of the issue however the relays do not engage now

 

[Perry Babin]

Is it producing audio on the output of the inductors before the relay?

Are you driving a signal into it?

 

[D132]

Would that be LA5?

Yes, 40hz signal through headunit

 

[Perry Babin]

That would be a good point.

 

[D132]

Sawtooth on LA5
LA 3 and 4 showed oscillation

Saw this near output, could this be a cap that leaked or glue, etc?

 

[Perry Babin]

What's the amplitude of that sawtooth. It may just be residual carrier.

On the output transistors, do you see modulation of the rail-rail square wave when you drive a signal into the amp?

I can't tell what that is from a photo.

 

[D132]

This (photo) is on LA5 and speaker output, seems to be about 5v with gain turned all the way down, amplitude changes with gain by a little

Yes there is square wave on both high and low side

 

[Perry Babin]

Is that while driving an audio signal into it?

If not, drive a signal into it.

If that's with a drive signal, try operating all pots and switches through their entire range to see if the audio returns.

 

[D132]

It was with driving signal into it

Half protect light is back

Gain changes amplitude still

Changing the subsonic messes with the wave a LOT and the amp makes a lot of weird chirpy sounds when changing it

None of the other pots did anything

Changing the switch to slave cleaned up the wave and wave gets blurry in master mode

 

[Perry Babin]

Blurry in master mode is likely right. It means that the pulse width is changing due to audio.

What could have changed from the time that there was no LED lighting? Trying to hit a moving target is very difficult.