PPBUS_G3H fluctuating

[Pedro147]

820-2879 green light on / PPBUS_G3H fluctuating from 12.61v down to 5.1v over a 6 sec time period and then straight back up to 12.6v and then repeats this. Short on an S3/5 rail ? If so how can I find it please? I am aware of diode mode and RTG measurements but not sure where to start looking. I have FlexBV and sch

[Pedro147]

Re: PPBUS_G3H fluctuating

No thoughts at all please ? ?

Am I using the wrong deodorant ? ?

[Pedro147]

Re: PPBUS_G3H fluctuating

I seem to be talking to myself here but here we go

I found that U7200 was getting hot https://www.youtube.com/watch?v=bgehLziPNxM so I replaced it with one from a donor board.
Now I have a steady 12.63v on PPBUS_G3H but some strange pin voltages on U7200.

1 - 0v
2 - 0v
3 - 2v
4 - 3.32v
5 - 2.04v
6 - 0.755v
7 - 3.32v
8 - 3.32v
9 - 7.75v
10 - 3.35v
11 - 3.32v
12 - 98.6mV
13 - 3.36v
14 - 2v
15 - 0v
16 - 12.63v
17 - 5.03v
18 - NC
19 - 0v
20 - 0v
21 - 0v
22 - 4.55v
23 - 0v
24 - 0v

Is this of any help in moving forward please ? Thanks

[piernov]

Re: PPBUS_G3H fluctuating

What's the issue now? What are the "some strange pin voltages on U7200"?

[Pedro147]

Re: PPBUS_G3H fluctuating

The 0v, 2v, 4.45v, 7.75v, 0.755v and 98.8Mv readings seem strange, but not really knowing what values these should have it's hard for me to know. Pin 15 is GND so that explains that I assume. Do these voltages look OK ?

I am asking what rails I should be checking next please Piernov.

I understand that this IC produces all the 3v3 and 5v power for the machine, and that it is a matter of other conditions being fulfilled to let logic gates to start allowing other rails to be produced IE, S5 > S4 >S3 > S0? There is obviously a logical choice of rails to check next but as yet I do not fully understand that logic and am after some direction please

[piernov]

Re: PPBUS_G3H fluctuating

My question was what are the symptoms of the machine now. Green light? Not turning on after pressing power button, fan not spinning at all?
As for power rails, well, you said it yourself, you have to check them in S5→S4→S3→S0 order.

Your measurements above already tell that PP5V_S5 and PP3V3_S5 are present but PP5V_S3 seems to be missing. But just extrapolating from that is not enough information to know what are the symptoms and what state the machine is in. Also always a good idea to tell what's the history of the machine.

[Pedro147]

Re: PPBUS_G3H fluctuating

Of course, sorry about the sketchy info. Yes green light on, no 5v at fan connector, unknown history and no apparent liquid damage. I haven't tried to start by SMC_ONOFF_L to GND, should I ?

[piernov]

Re: PPBUS_G3H fluctuating

Yes you have to trigger power button to turn on the machine.

[Pedro147]

Re: PPBUS_G3H fluctuating

I didn't try seeing as there is no 5v at fan connector but I will try that after work. I assumed, possibly incorrectly that will not start if the fan isn't getting power? Thanks

[piernov]

Re: PPBUS_G3H fluctuating

But fan won't get power if the machine isn't turned on.

[Pedro147]

Re: PPBUS_G3H fluctuating

Oh I thought that it would I am not the brightest - I need to watch more Paul and Louis videos Thanks I'll try after work

[Pedro147]

Re: PPBUS_G3H fluctuating

Well I made a faux pas on Louis' Discord Macbook repair channel and got stopped from posting. I wasn't aware of the four mention rule when I was thanking you guys for your help. I might post the full text of that post here in case you still feel like offering any help Piernov
@friendly#6525 thanks. I don't mean to be a PITA forum hopper but piernov helped me out on badcaps forum this am (Aussie time) I was asking about my measured voltages on U7200. He asked me if I had tried to turn it on (by SMC_ONOFF_L ) This is where I got confused seeing as the 820-3330 has fan spinning without doing that as you have kindly told me.
I just turned this 820-2879 on and U1000 and U1400 started getting hot. I monitored for a 3v-0-3v pulse on PM_PWRBTN_L which I got not unsurprisingly. I disconnected quickly because I had the heat sink off to allow access during all the probing and chip replacement I have been doing. I just turned it on briefly again and I have 5v at fan connector but fan not spinning. Not sure if it's faulty (fan) or there is an issue with the PWM speed control? I assume that I cannot just test the fan by applying 5v and GND because of the PWM? It looks like there may be a voltage divider and a FET involved in fan speed control.

After I refit the heat sink (with thermal compound) I might check for a 3v-0-3v pulse on PM_SLP_S3_L and PM_SLP_S4_L

Any further clues greatly appreciated please guys and thanks for all the help so far @2informaticos @ChrisB @friendly @Inwerp and @piernov (hope I didn't forget anyone )

[piernov]

Re: PPBUS_G3H fluctuating

Apple Core 2 Duo machines need the power button to be triggered to turn on, they won't turn on automatically when Magsafe is connected with no battery.

If CPU and MCP are heating up, the machine is turning on, so it's reaching an S0 state and there's nothing wrong with PM_SLP_S4/S3_L.
Fan not spinning can be due to multiple reasons, but you should plug a speaker to check for chime and display to check for image.
I think you can apply 5V to the fan and it should spin (PWM left floating, should be pulled up inside the fan so should run at 100% when disconnected).

[Pedro147]

Re: PPBUS_G3H fluctuating

Thanks Piernov I'll try after work and post back. Looks like I may be getting close

[Pedro147]

Re: PPBUS_G3H fluctuating

I just realised that I forgot to finish my posting here. Well I got it going after Chris Busillo on the FB Macbook logic board repair group suggested replacing the U6100 ”BIOS” chip. Thanks for the help @Piernov