820-3481 - LED 1 blinking

[Palhano]

Board with LED always on, when I press power, LED 1 blinks.

I'm using the data from 820-3478!

Replaces the Q8450 and U8470 (FET_EN_P12V_S5 has 11.1v, even after changing)

Any tips?

 

[2informaticos]

You should use 00291, or 3482 schmatics instead.
Also, 3299 uses the same GPU; when need to work on its area.

Do you get stable 3V3_S5?

 

[Palhano]

Thanks for the tip with the schematic!

I re-soldered the U8470, the iMac turned on. I'm testing it now.

 

[Palhano]

It worked for a few hours and stopped. Having the same problem, LED 1 blinking.

I went to start checking the lines, it started working again. When there is a problem, 3V3_S5 is stable.

 

[2informaticos]

Try another Q8450; NOT recovered from other board.
Be sure to get proper solders.

 

[Palhano]

I replaced the Q8450 once again, both times with new components! the problem continues!

 

[2informaticos]

"LED 1 blinking"
Which is that in the schematic used?

 

[Palhano]

The schematic informs S5 (LE0301) (what did you ask?)

Note: LED blinking when I press the power button.

 

[2informaticos]

If 3V3_S5 is really stable, that LED shouldn't blink.
Check if 12V_S5 is flat, no drops.
You may need to change Q6970; do it, just in case.

 

[Palhano]

Sorry, I think now I understand.

3V3_S5 is stable. When I press the power button, it drops and goes back to 3.3v. The 12V_S5 has no drop.

Do you recommend somewhere to buy the Q6970? I can't find it anywhere.

 

[2informaticos]

If no drop detected at 12V_S5, Q6970 should be good.
However, I recommend to change it, if you are not sure.
It should be available somewhere on Internet...

 

[Palhano]

I can't change the Q6970, I can't find this 649135PBF anywhere to buy.

But the iMac decided to work and has been working for two days, I'm testing it.