Some not-expected continue to this project :-D

Received two video's for repair yesterday, 9800GX2 (one of GPU's not detected) and 7800GTX 256 totally dead, "for parts"

First check of 7800GTX..



Huge hole in PCB, where one of MOSFET's was on GPU VRM :-D Wow...about 4 layers inside was just broken... Shortcurcuited 12V to GND.
Had to drill hole even bigger, to remove SC :-D

Next step...yeah, took 4870 DC-DC "piece of card" and set up 1.3 Vgpu, 2.2Vmem volts on it. Checked and hooked up, replacing stock power inductors.



Checks....Volts are ok...

Plugging 7800GTX Radeon Edition into test rig..



Beeeeep-bep-bep-bep.....Damn, no post, no VGA. Volts are just fine, it's not problem with them.
Had some thinking for hour or more...looked thru all the PCB, checked similar 7900GTX dead, no broken parts...

Then remebered, there is quite advanced PWM controller on 7800GTX-es, Primarion PX3535 3-phase. And it has Powergood signal like, to keep GPU in reset during power-on sequencing and stabilisation. Oh ,yeah, finding pinout of this PX3535, here we go...there is open-collector line with similar signal name. There is pull-up resistor to +3.3V just next to necessary pin. Measured voltage on it = yes, it's 0 V (Logic 0) here!. Cutting with knife that pin from signal, and again check...And YES, it's 3.3V now, Logic 1, Now GPU will think , "Power is OK" always :-D



Putting card to test rig....Beep.....WOW...even forget to connect monitor output ...Hooking it up and...



Welcome 7800GTX-256 Radeon power Edition :-D Worked without a single artifact. Will hook chiller cooling on card and change CPU to better, and will hunt some hwboints on it