820-3435 Tries to turn on can't, quarter spin

[aprendiz]

CPU Vcore also pulses????

 

[JohnB8812]

Did not check CPU Vcore yet. I would assume so, but I will do that when I get back to the board

 

[aprendiz]

As Duke always says, this could be anything, corrosion somewhere, under CPU, SMC,traces and/or resistors on SPI>SMC or SPI>CPU, U1900 (replaced)...

 

[JohnB8812]

I kinda figured as much. Going to do what I can these people who sent it to us get a sweet deal (aka we don't make shit) so spending more than an hour on their stuff is really not the best idea. Going to check tho if CPU Vcore is cycling what would that mean?

 

[dukefawks]

If CPU Vcore pulses then it is usually U6100 and termination resistor/traces problem.

 

[JohnB8812]

Ok will check that. I'm going to guess it will pulse seeing as there was corrosion left on the ROM

 

[JohnB8812]

All the rails kind of fluctuate once the fan comes on. For example if the fan goes off PPBUS goes to 8.38 then once the fan comes on it stabilizes to 8.59. CPU Vcore will go all the way to zero when the fan is off then pulse as high as 3.7 volts then stabilize when the fan spins at 1.75

 

[JohnB8812]

Wasn't stuff under the SMC tried that.

 

[dukefawks]

Corroded traces to U6100 are most likely at this point. Check all termination resistors and traces going to U6100.

 

[JohnB8812]

Termination resistors and traces are good. HOWEVER, I just found that I never get 3v42 on U1950 at ALL. Does this mean U1950 is fucked or does this mean there is something up with 3v42? I do get a steady orange light at all times

 

[JohnB8812]

Actually nevermind I got it scratch that. I did measure the resistors and traces and every single one of them connects

 

[JohnB8812]

I'm going to jump pins 7 and 8 and see tho. The trace doesn't look burned at all, but that was where the original corrosion was when I got the board

 

[JohnB8812]

No change. Every single trace on the BIOS connects to its corresponding spot. Same with resistors. They all measure in spec, and there are no obviously fucked probe points really on the entire board for that matter.

 

[dukefawks]

Can you take a good hires picture of U6100 area?

 

[JohnB8812]

No Title

 

[dukefawks]

I assume you already ripped off J6100? Pull the BIOS chip and do a diode mode reading on each pin. Try another known good BIOS for testing, can be from 3435 or 3437.

 

[JohnB8812]

Yes JTAG has been eradicated lol. I will post diode mode readings tomorrow and try known good bios.

 

[JohnB8812]

Swapped ROMs and still doing it. I'm gonna call this one because don't have a lot of time left with this one. Any other ides what could cause it? Rest of board looks very clean

 

[dukefawks]

Only thing I'm still suspecting is a problem around U6100. Still not seen the diode mode readings.