Macbook 820 3115 No 3v42_g3h line, no short

[BrickBreaker]

This was a Water Damaged board. After looking at where the damage was, mostly around U7000/ ISL6259, I ultrasonic cleaned it, and started repairing. Only one thing stood out visual check, R7052 fell off very easily. And pad under pin 2 on R7052 was gone but replace the resistor, scrape at the trace, and fixed. As the title suggests, this board has no fan, no light. Looking at 3.42 circuit, I found U6990 wasn't doing it's job (I think). So I replaced it. This guy is getting voltage but not sending out 3.42V like it should. Here are the measurements now.
U6990
Pin Volts
1 0.862
2 0.624
3 0.043
4 0.987
5 0.000
6 0.510
7 16.99
8 0.627
9 0.510
10 0.921

[BrickBreaker]

Re: Macbook 820 3115 No 3v42_g3h line, no short

Audiomodder, I will go through Louis' videos some more, but from him and the schematics it seems to me that U6990 should generate 3.42V g3hot line from either charger or battery voltage and send that to U6901. With that 3.42V line and SMC_BC_ACOK line both reaching U6901, then U6900 gets the message that it can turn on the light on charger.

[piernov]

Re: Macbook 820 3115 No 3v42_g3h line, no short

Pin 4 EN should be 17V as pin 7 VIN is. Look closer for broken traces around the chip or bad soldering.
If nothing looks wrong to you, take a clear high definition picture of the chip's surroundings.

[BrickBreaker]

Re: Macbook 820 3115 No 3v42_g3h line, no short

After watching Louis' 'How does PP3V42_G3H circuit work...' video and he says U6990 rarely goes bad. Thinking about renaming my problem "PP3v42 low (0.5V)" since that's what it's measuring now. Measured above on pin 6 U6990 and I measured it on the inductor (L6995). What's pulling it down?

Just replaced ISL U7000 as I was drafting this reply. No change, still 0.5V 3V42 line, I'm thinking SMC is to blame.

[BlueMidnight]

Re: Macbook 820 3115 No 3v42_g3h line, no short

You have the right idea about the relationship between U6990/U7901/U6900. I know you mentioned in the other thread that you had 3.42V, but now you don't. A bad SMC is a possibility if you have 3.42V but not SMC_BC_ACOK (which you apparently never got the chance to measure before it lost 3.42V?). You'll have to cross that bridge when you come to it. Right now, U6990 isn't functioning at all, and it doesn't require the SMC to do so.

First thing is to make sure U6990 is getting voltage on both pins 7 and 4 (as piernov mentioned). Also check the trace from pin 3 to R6995 and from that resistor to PPVIN_G3H_P3V42G3H. The easiest way to check that is probably to just ensure pins 4 and 7 of U6990 have direct continuity to pin 3 of D6990. Pin 3 of U6990 should have 1Mohm of resistance to pin 3 of D6990.

If U6990 is connected properly and enabled, you should see various voltages on pins 1-4, 7-8, and 10. And then finally, if there is nothing shorted (i.e. the current drawn is not above the maximum allowable) on the output, you will see the 3.42V on pins 6 and 9.

[BrickBreaker]

Re: Macbook 820 3115 No 3v42_g3h line, no short

U6990 is not getting voltage at pin 7 (0V) however pin 4 has 3.42V. Pin 6 is visible corroded so I'm gonna lift U6990, check continuity and such. Get back to this tomorrow.

[BrickBreaker]

Re: Macbook 820 3115 No 3v42_g3h line, no short

Disregard that last post, sorry. Okay so there was a broken via connecting to R6995 on other side of the board. Made a hole and connected that back up, now U6990 seems to be working, sending out 3v42. I measure U6901 and get the following

U6901
1 3.100
2 3.100
3 0.000
4 0.691
5 3.427

[BrickBreaker]

Re: Macbook 820 3115 No 3v42_g3h line, no short

0.691 Sounded low to me for SMC_BC_ACOK_VCC so I replaced U6901. I know I know monkey see monkey do. Blah blah blah there's a short to ground on that line. Replaced U6900 and short is gone. SMC_BC_ACOK_VCC is 3.456V, still no light on charger. Sorry I'm just documenting everything as I go in this thread.

[BrickBreaker]

Re: Macbook 820 3115 No 3v42_g3h line, no short

PP3v42_G3H is 3.457V. PPBUS_G3H is 12.23. No PP3v3_S5... Someone explain this circuit. 5V_S3 and 3V3_S5 are both generated by U7200? 0V on enable line for this chip.

[BrickBreaker]

Re: Macbook 820 3115 No 3v42_g3h line, no short

Alright last post for today. I replaced Q7221 because it had voltage in (pins 2 and 5) but no voltage on pins 3 and 6. After replacing Q7221 I have
Q7221
Pin V
1 0.0
2 3.42
3 0.0
4 0.0
5 3.40
6 0.0

Although, is that to be expected? Are P5vS3_EN_L and 3V3_EN_L too high at 3.4V? Therefore Q7221 is not getting enable signals at this voltage? Gonna have to chase down those lines on Monday.

[BrickBreaker]

Re: Macbook 820 3115 No 3v42_g3h line, no short

Oh no, PM_SLP_S4. That's the end of the road for a lot of boards, right? Looking forward to digging into this next week.

[BlueMidnight]

Re: Macbook 820 3115 No 3v42_g3h line, no short

Yes, U7200 generates those voltages by controlling the pair of MOSFETs on each rail (Q7220 and Q7260/Q7261). The enable signal comes from the SMC, but that won't happen unless the onewire circuit is working. And if the charger light is still off, then the onewire circuit is not working.

Q7221 was okay. The SMC was holding both "EN_L" signals high. This turns on both MOPSFETs and pulls both ENTRIP pins on U7200 to ground, which disabled the switching 3V/5V outputs.

Check the onewire circuit again. You've made a lot of progress, but something still isn't right there.

U6900 is an ESD safety device. It will connect the INT and EXT pins together only when it is powered up via the VCC pin (which it is now). R6929 is a pull-up resistor for that line. Make sure you don't have another bad trace. Follow pin 4 all the way back to the SMC. Follow pin 5 all the way back to the charger. If it's plugged in, you should measure 3V the whole way.
Alternatively, you can unplug the charger, and measure continuity for each half of the onewire circuit (remember that U6900 will not connect each half of the onewire circuit if the power is unplugged).

[BrickBreaker]

Re: Macbook 820 3115 No 3v42_g3h line, no short

Thanks for replying. PPBUS_G3H was 12.2V SMC is definitely bad. Going to do replacement when new parts boards arrive.