GAS PSP3500.1d going into protect

[LatvianVideo]

Hello, repairing my brothers PSP3500.1D (or trying to). Issue in the title.

Tools I have: Multimeter (has diode mode, beep, etc), soldering iron

How it happened: He was listening to music at a low volume, shut off the car and went to the shops, when he came back the amp was dead.

What I've done: Opened it up, found a IRFB7437 with the drain leg melted (see image below). Its 4.7ohm (4R7) gate resistor also was dead. Replaced both, still goes into protect.

Diagnostics:
There is no short between the RCAs and speaker outputs
There is an increasing resistance (goes from ~0 to ~135ohm) between the power and ground terminal.
There is an increasing resistance (goes from ~0 to ~135ohm) between the drain and source (2nd and 3rd pin left to right) of all these fets (see image)
Rest of the fets seem fine

Other side of the amplfier:

I hope we will be able to find the issue, thank you in advance.

 

[Perry Babin]

Did you check the output FETs on the other side of the board?

 

[LatvianVideo]

Yep, checked all of the fets on the sides of the board, all seem ok

 

[Perry Babin]

It may have had a random failure of one of the driver ICs.

What are the audio driver ICs?

Good quality photos would be helpful until someone who knows this amp can help.

 

[LatvianVideo]

I did check the mosfet driver model before, its a 27324, gonna take some HQ pics in the morning (like 10h maybe)

 

[Perry Babin]

The IC driving the 27324?

 

[LatvianVideo]

the INa and INb of the 27324 go to the PIC16F1829

 

[LatvianVideo]

And checked with my very DIY osciliscope, the middle pin of the fets circled in the picture posted before gets 12v DC (remote not connected). Ground was connected to the chassis. No change when remote gets connected. Didnt see any DC voltage on the output terminals

 

[Perry Babin]

DCV on pin 1 of the PIC16F1829 MCU?

Do you have a square wave on pin 2? If so, frequency?

 

[LatvianVideo]

Yes, about 5v on the pin 1

Unknown freq on pin 2, as my oscilloscope is an arduino 😂

heres a screenshot from the UI, maybe can calculate it, as the time is known, the voltage is going thru a ~65.5x voltage divider as i didnt know how high of a voltage i would be dealing with on the rails

 

[Perry Babin]

Do you have the diagram for the amp?

The scope display isn't useful or the output is wrong. It should be an 80kHz signal. With the scope set to 5us, you should have only about 4 complete cycles.

 

[LatvianVideo]

I do not, online i couldnt find anything about the amplfier. The oscilloscope isnt good because its not supposed to be an oscilloscope, its an arduino, lol

 

[Perry Babin]

Does your multimeter read frequency?

 

[LatvianVideo]

it has a hz function, but either i dont know how to use it, or it just doesnt work

 

[Perry Babin]

Can you post a high resolution photo of the MCU and the area around it?

What are the transistors that are being used as a buffer between the 2010 audio driver IC and the output transistors?

 

[LatvianVideo]

Not very high res, so just took more, but closer shots. Basically took shots of the entire board

 

[Perry Babin]

I've been trying to find a diagram that's close and this amp is a lot of parts from the Brazilian amps, unfortunately, a lot of different models.

I'll keep looking. Hopefully someone will see this and is more familiar with the Brazilian amps than I am.

If you try to power up, at the instant that you apply remote voltage, do you see any sort of pulses of DC or square wave on the inputs of the 27324 PS driver IC?

Does it go into protect before you apply remote voltage?

 

[LatvianVideo]

It only powers up and goes into protect when the remote voltage is applied. No remote is no power up like it should be.

I dont see any dc voltage, but i do see pulses of something, possible that its square wave that is too fast for the arduino. The pulses stop after the amp goes into protect. It goes like: remote applied, then the 3 leds (power, clip, protect) turn on after eachother, until the power and protect start flashing.

 

[Perry Babin]

Do you see a pulse of (or steady) DC voltage on the output of the rectifiers as you apply remote voltage?

 

[LatvianVideo]

not sure which ones you meant, but from what i tested, i didnt see much. Only now noticed there is an voltage regulator going to the 2 IR2010S, that regulator isnt getting any supply