Search results

Can I ask what programmer would you recommend to flash the BIOS on this iMac?

Alright, looks like the issue was U8450. I replaced Q8450 but it didn't fix the issue until I replaced U8450. Hopefully this is all that's going to be needed. Should I check or replace any other components?

I get 0V output on Q450 (Pins 1, 2, 3). I also have 0V on FET_EN_P12V_S0 (Pin 4). I do get 12V on PP12V_G3H_P12V_S0 (Pin 5). Just in case it helps, U8450 voltages are as follows: Pin 1: 11.97V, Pin 2: 1.77V, Pin 5: 11.97V, Pin 6: 0V, PIN 7: 0V, Pin 8: 0.051V. On R8542, Pin 1 has 3.3V (Pin 2...

On U8410 Pin 8 I have 1.0V. The voltages for U8500 are: Pin 1: 3.325V, Pin 2: 3.322V, Pin 3: 3.325V, Pin 4: 3.325V, Pin 5: 3.325V. Pin 6: 3.325V, Pin 8: 3.271V, Pin 9: 3.325V, Pin 10: 3.319V, Pin 14: 3.326V

Alright, I checked R8410 off the board and it came in at ~10K Ohm like it should. So I replaced U8500 as recommended and now I get 3.3V for PM_PGOOD_FET_P1V0_S3. However, the board still won't power on. Should I replace U8410? I suppose I can go back and recheck all the other voltages.

Ok, hopefully we're looking at the same schematic. Pin 2 on U8500 is fed off U8410 Pin 7. There is a 10K resistor, R8410, with PP3V3_S5_PWRCTL on one side and PM_PGOOD_FET_P1V0_S3 on the other. Both voltages are nominal: 3.3V for PP3V3_S5_PWRCTL on R8410 Pin 1 and 1.0V for...

Ok, I measured Pin 2 on U8500 again. It is 1.00V. The schmetics say Pin 2 is PM_PGOOD_FET_P1V0_S3, so wouldn't that be the proper voltage?

U8500 Voltages: Pin 1: 3.324V, Pin 2: 1.00V, Pin 3: 0.00V, Pin 4: 3.324V, Pin 5: 0.016V. Pin 6: 0.00V U7350 Voltage Out (Pin 1 & 2): 0V U8410 Voltage Out (Pin 8): 1.00V I can't see why U8500 Pin 10 and L7310 should have the same voltage, but the readings are the same: U8500 Pin 10: 0.013V, L7310...

I wasn't sure that some voltages might not be able to be measured to common ground due to diodes restricting voltage direction. But I suppose the schematics would show where that was the case? I'll post the other voltages as soon as I get a chance.

Voltages on U8500 - Pin 8: 0V, Pin 9: 3.3V, Pin 10: 0.013V, Pin 14: 3.3V. These are all measured to ground.

If I measure L7310 to ground I have 0.048V. Is that what I should be measuring it to? The only reason I mentioned the ohm value was to see if you thought I had a short. I'll measure the voltages from U8500 in a bit and post those.

PMP_SLP_S3_L is at ~3.3V. L7650 is ~5V to ground. L7310 is at ~5V to L7650.

If I measure PM_EN_FET_P12V_S0 to ground I get about 240 Ohm. So if I measure the voltage to PP12V_G3H on U8450 I get ~12V, which stays steady if I short J5120. Yes, I agree that I need assistance in understanding schematics. If you have any suggestions on a guide that would help me, I would...

I see the voltage drop on PM_PWRBTN_L when triggering SMC_ONOFF_L, 3.3V -> 0V -> 3.3V (using J5120). PM_SLP_S4_L stays at 3.3V when triggering SMC_ONOFF_L, unless I short it (at J5120) until the board turns off, then it drops to 0V. PM_EN_FET_P12V_S0 stays at 0V during all of this. I measured...

Ignore the 23.17V reading, that was a mistake on my part I think. I found PP12V_S0 and FET_EN_P12V_S0, on Q8450 and U8450, and they are both missing (0V) but PP12V_G3H is present.

Ok, I will take your advice regarding the BIOS chip. There is no PPBUS_G3H on this iMac board. I think the equivelant P3V3_G3H. On C6922 I get 3.7V. On U6970 I get 3.8V on PIN 8, P3V3_S5. Pin 7 which is FET_EN_P12V_S5, I read 23.17V, which is obviously not good. All other values on U6970...

Thanks for the quick response. Unfortunately, I've gone out of town, but I'll be back in a couple days. I'll post the info as soon as I get back.

So, I got a 820-00597 logic board to replace the one in a 2017 21.5 4K iMac. It worked fine when I got it, powered up fine, was able to install MacOS on it. All done on the bench of course. I decided before putting it in the chassis to reapply the thermal paste for the CPU and GPU and look...

I appreciate the reply and the info but, unfortunately, I blew the die right off the chipset. Was pretty cool I guess. But yeah, this motherboard is toast.

Hello, I have an 820-00597 Logic Board from a 2017 21.5 inch iMac. I bought this board as-is so I don't know the history. There were two electrolytic caps that were broken off that I replaced (C6515 & C6526), other than that I can not find any damage. I'm bench powering this board, and my...