Trying to repair a power supply of an active speaker, Class D

[Yamin]

Hi guys,
I've got a RCF art735-a in for repair which went through a power surge. The half bridge driver IR21531 was fried with the top chipped off. One of the mosfet was shorted along with few other components.

Luckily I had the exact same board with the amplifier section fried. So I started replacing the power supply components from it.
Here's what's happening now- The power supply is not starting up. There's no voltage at VCC pin of the IR21531.

First question- Is it okay to turn on a class D amplifier without a load connected? I'am just trying to check whether the power supply works, and I do not have an input signal applied.
I have attached a diagram of the effected area/ and noted the components changed. I also changed Q6 as it was shorted too (shown in the picture), not sure how its used.

What I have noticed is on start up the supply voltage is dropped across 'the start up resistors and there is no voltage at VCC. Why could this be?
I checked across VCC and COM (of the chip) with diode mode and I get a reading of 0.2V! with probes either way. Could this be a problem?

Thanks in advance for the help

[capt bullshot]

What I have noticed is on start up the supply voltage is dropped across 'the start up resistors and there is no voltage at VCC. Why could this be?
I checked across VCC and COM (of the chip) with diode mode and I get a reading of 0.2V! with probes either way. Could this be a problem?

Yes, this is a problem. I'd expect either ballpark 0.7V (reverse) or something like open (forward) with a diode tester here. Look for more damaged components, or your replacement chip is fried.
Usually this kind of IC releases the smoke if they experience high voltage at their outputs as a result of a shorted / failed MOSFET, I'd expect both MOSFETs blown, other components may also get damaged.

With modern stuff, I'd assume it's safe to operate the amp without load - don't quote me if it wasn't

[PKTKS]

(.)
First question- Is it okay to turn on a class D amplifier without a load connected? I'am just trying to check whether the power supply works, and I do not have an input signal applied.
(.)

Depends mostly on the supervisor.. and YES definitely you should use a load.
Several supervisors are bounded to the specific load they were designed to.

And this is a major problem as we all should or want to know if
disconnecting the loads the supervisor will soft start... or not.

This is a common problem diagnosing SMPS and one of the
drawbacks of SMPS as well. Components age and soft start may fail.

Or just a dead short is causing the issue.
Typical SMPS waste of time.

Paul