Xtant 6.1 repair

[lumanauw]

I got this Xtant 6.1 which is not working. The rail voltages are there (+/-54V), but there is nothing on the gates of audio output mosfets.
Anyone familiar with this amp? It seems classD.

 

[Perry Babin]

It looks like it's very similar to the MTX6500. If so, the circuit would be similar to the Sony amps. I'd need to see more detail to help.

 

[lumanauw]

Hi, Perry,

Here I take some pictures. There is LM311 sitting at -54VDC as it's ground reference. I don't know if it is the main comparator, or part of protection circuit.

 

[lumanauw]

If it's based on MTX6500, there is LM311 on negative rail 🙂

 

[Perry Babin]

It's part of the over-current protection. It's sitting on the negative rail and senses voltage across the 0.22 ohm resistors that are between the negative rail and the source legs of the low side output transistors.