Need help to fix this amp DIY

[Joseph R]

Hi,

I had to check for a friend an amp he got from a passed away preamp and amp builder in UK and discovered that the ferrite core was broken.
The amp was still working up to 300W RMS but not more. The amps is designed to give 600W RMS.
I did replace the core with same type and before powering up I saw one cable disconected. Unfortunately I dont know where this one has to go.
I tried the amp without connecting it and the sound is cutting now at regular rate of about 3 to 5Hz.
I mesured -70V on this cable, its the one with the red circle on picture.
There is another cable coming from same location on PCB that goes on pin3 of the left bank of the IRF640 ( blue arrow ).
From what I guess the disconnected one must go somewhere on those IRF640 on the right.
Can someone help me?

[RealForce]

WoW what a mess
I am wondering how it works at first place

[hardwareguy]

Judging from what I see, my first suspect would be a broken cable or wire somewhere. Check for broken solder joints at those point to point wired transistors.

Also, make sure all caps in the signal path are OK.

[Joseph R]

I finally had time to make a schematic of the beast.
On two IC the type was scrached off by the builder who didnt want that other people copy his work.
Anyway I still have this problem that the amp is cutting the sound at a slow rate of about 5hz.
Can somebody please help me to find out what could be those two ICs and obviously the problem.
For info it was build 15 years ago.

[Joseph R]

No one can help me?
I can make some mesurements if it can help.
And what is the function of ICL8211?
I really need this amp to be working.

[Joseph R]

Ok after leaving this amp alone for some time know I back on it and want to bring it alive again.
Can the gate driver be IR2010 or 2110?
And what's the use of this ICL8211? over current?

[Joseph R]

I did find out that ICL8211 is for under voltage condition. Isn't this a little bit weak for protection?

[Eva]

Wow! Self oscillating class D with point-to-point output stage...

Bad news: This thing probably never worked right. For technical reasons.

[Joseph R]

Yeah i know it looks terrible but it did work many years without probs. The man called barracuda and build many ampy this way. I have three different amps from him and all three are a different topology.
These amps are for driving super scooper subs mogale style in the reggae dub scene. These amps are a real piece of history.
But eva do you think it could be an ir2010 gate driver? Pinout looks compatible but as i dont have much knowledge in classd. Only the high side has pwm on output but nothing on the low side.
Does somebody need that i make some scope measurment to help me?

[Centauri]

IR2010 or 2110 would seem feasible for U4 - check the waveforms on the input pins 10 & 12 of this chip. U3 looks as though it shorts the input drive if the supply voltage on U4 is too low, so could be a form of soft start. U2 is probably a dual optocoupler, something like the ILD74 for instance - looks to perform output current limiting.

Certainly a wild looking construction ......