MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powered

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

My regular programmer is a SVOD3 but it's a bit expensive if you aren't doing EC programming. I also have a T56 for some of the other stuff, but the interface is a bit convoluted compared to the SVOD. RT809F comes highly recommended by others but I haven't used it.

If you are looking for donors, use eBay for either faulty units or boards. Aliexpress boards are usually raped for anything useful. SMC's off these boards are normally corroded/delaminated. Only good for passive components or connectors really.

Thanks for the info. Will check out some of those models and see what will work for me. For now I have purchased a CH341A USB programmer and SOIC in circuit clamp, along with a WSON/USON adapter which looks like it should work as a temporary measure. Only a few dollars, so not a huge loss if it doesn't work well.

RE donor boards: yes learned my lesson with AliExpress donors lol. As you say, most good stuff is raped from board, and the rest are overheated, and normally all smeared to one side of the board, so not very useful.

[reformatt]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

My regular programmer is a SVOD3 but it's a bit expensive if you aren't doing EC programming. I also have a T56 for some of the other stuff, but the interface is a bit convoluted compared to the SVOD. RT809F comes highly recommended by others but I haven't used it.

If you are looking for donors, use eBay for either faulty units or boards. Aliexpress boards are usually raped for anything useful. SMC's off these boards are normally corroded/delaminated. Only good for passive components or connectors really.

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

https://boards.rossmanngroup.com/thr...o-chime.58384/

Thanks @mon2. See my response to reformatt. I don't have a programmer, but going to try that and a possible SMC swap if I can find a cheap doinor board. (Anywhere you know of other than AliExpress lol?)

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

You previously mentioned broken pin on RAM slot and you've also replaced the SMC. Are you sure the SMC you used is any good? Maybe reball the old one and put it back on. Review and triple check all your other work before proceeding further.

I haven't replaced the SMC. I reballed the one that was on the board. I could try to change it, but I don't have any donor board at this stage. I will recehck my other work as well just in case, and going to check all of the power rails again to make sure there isn't still another issue.

With the RAM, it should however boot on the one slot that is ok though (would beep at you otherwise).

Yeah thats what I was hoping to do. If I managed to fix the board, I would just use the one remaining slot, but the board doesn't even beep with no RAM at this stage.

Maybe try known working Clean ME BIOS on U6100. Boards for this model are pretty cheap though if you want to toss it onto the donor pile.

What programmer do you recommend? I don't have one at this stage, and been wanting to get one but not sure what to get. Also is there a repository of known good BIOS files for each model somewhere, or is it a Google adventure each time?

[reformatt]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

You previously mentioned broken pin on RAM slot and you've also replaced the SMC. Are you sure the SMC you used is any good? Maybe reball the old one and put it back on. Review and triple check all your other work before proceeding further.

With the RAM, it should however boot on the one slot that is ok though (would beep at you otherwise). Maybe try known working Clean ME BIOS on U6100. Boards for this model are pretty cheap though if you want to toss it onto the donor pile.

[mon2]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

https://boards.rossmanngroup.com/thr...o-chime.58384/

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

The joy was a bit short lived lol. After putting it into a chassis, theres no chime at power on, no display, and fan spins at full speed. Joy lol

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

CHGR_ACOK is open drain output so is being pulled low by the ISL because of the bad input to pin 2. It is irrelevant till you sort that out. You may have introduced other issues though from component replacements.

Thanks for your help @reformatt. I replaced R7005 with a 20 ohm, and I got fan spin, and green light on charger

[reformatt]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

CHGR_ACOK is open drain output so is being pulled low by the ISL because of the bad input to pin 2. It is irrelevant till you sort that out. You may have introduced other issues though from component replacements.

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

Sorry, correction: R7005 on the working board measures 130ohm, not 1k. Measured the wrong one.

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

Not sure what your logic is re DC IN board since there is a diode in between, but R7005 is clearly faulty.

Yeah I am trying to find a replacement. The working board's R7005 measures 1kohm, so what should I replace it with? 20 ohm as per schematic, or as per other board 1k ohm?

Regarding the logic with removing the DC IN board, only mentioned it as it has caused different readings with some values for me in the past, so now I remove it before taking any measurements.

Regarding SMC_BC_ACOK, it is still short to ground when the board is powered, which is not correct either I am guessing. Measured using diode tester to ground (positive terminal on ground) it measures a 0.5v drop, but the minute I connect power to the board it direct shorts to ground.

[reformatt]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

Not sure what your logic is re DC IN board since there is a diode in between, but R7005 is clearly faulty.

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

So if the output of D7005 is ok, that means from your earlier statements you have a 14V drop across R7005? Check R7005 resistance and resistance to ground from pin 2 of the ISL.

I rechecked D7005, and yes 16.5v on each ping 1 and 2, and 16.3v on pin 3. Pin 2 of U7000 measures 2.4M ohms to ground (without a DCIN board attached), but the resistance drops constantly until it stabilises at around 1.6M ohm after about 30 seconds after unplugging the power. I removed one pin of C7005 to take it out of circuit, and R7005 gives and immediate value of 300ohm without any fluctuation in value.

R7005 measured inline without a DCIN board attached reads 50k ohm to start with also drops for 20 seconds or so until it stabilises at around 1k ohm. According to the schematic I have, it should be 20 ohm, so must be something else inline that is throwing off the reading.

[reformatt]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

So if the output of D7005 is ok, that means from your earlier statements you have a 14V drop across R7005? Check R7005 resistance and resistance to ground from pin 2 of the ISL.

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

Check D7005.

Don't replace components en masse unless you have a valid reason. This is a good way to introduce additional faults and then it makes it difficult to help.

All troubleshooting should be done with adaptor only; if you are chasing anything to do with Magsafe, you should always use an original adaptor, trust me.

Thanks @reformatt. I understand, however I don't actually have a magsafe charger for this model sadly, so have no choice at this stage. Also I have no way to tell what current the board is drawing if I use the actual charger.

As far as replacing componenets, I only changed what seemed to not be giving correct outputs, but as you say, this could have introduced other issues, so will slow down on the replacements for future fixes.

Edit. Forgot to mention. D7005 is good Measured with diode test mode. When powered it has 16.45v on both inputs, and the same on the output

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

This is major. Review this area carefully. Start with removing all power. Meter in resistance mode.

Check the resistance from the measured pin to a point where you know the power rail is ok. Again no power. This could be trace break or similar.

Compare each measurement to the known good board.

Time for beauty sleep here...my basketball team lost (western semi-final). will check the forum in the morning. Your last post has some good areas to investigate.

For now, do not replace u7000. It may be ok.

Fair enough. Thanks for the help so far. Hopefully I will have found the issue by the time you wake up lol

[reformatt]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

Check D7005.

Don't replace components en masse unless you have a valid reason. This is a good way to introduce additional faults and then it makes it difficult to help.

All troubleshooting should be done with adaptor only; if you are chasing anything to do with Magsafe, you should always use an original adaptor, trust me.

[mon2]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

PPCHGR_DCIN (Pin 2 of U7000) = 2.36v - This measures 15,9v on the working board

This is major. Review this area carefully. Start with removing all power. Meter in resistance mode.

Check the resistance from the measured pin to a point where you know the power rail is ok. Again no power. This could be trace break or similar.

Compare each measurement to the known good board.

Time for beauty sleep here...my basketball team lost (western semi-final). will check the forum in the morning. Your last post has some good areas to investigate.

For now, do not replace u7000. It may be ok.

[duwane]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

OK. PPBUS_G3H is still a suspect when powered by your external power supply only.

1) Confirm that you have PP3V42_G3H_REG with ONLY the external power adapter (your BY cable should be fine).

Agreed. It is doing my head in lol. I have already replaced it 3 times with new chips, so highly unlikely to be a bad chip, but could be possible I guess.

PP3V42_G3H_REG = PP3V42_G3H = 3.45v as measured @ pin 1 of C6999

2) See post #2 of this thread and review the voltage @ CHGR_ACIN.

CHGR_ACIN (@pin 3 of U7000)= 3.86v - About the same on working board.
PPCHGR_DCIN (Pin 2 of U7000) = 2.36v - This measures 15,9v on the working board, so this could be the main issue. Will investigate this further in bit.

Based on the non-existent PPBUS_G3H with the adapter only case, U7000 is not operating properly - for some reason.

Also, be sure that U7000 is being powered via

PP5V1_CHGR_VDDP
PP5V1_CHGR_VDD
PPCHGR_DCIN

PP5V1_CHGR_VDDP & PP5V1_CHGR_VDD both measure 2.86v. The test board measures 5v for these two, so we have an issue here too grrr.
PPCHGR_DCIN: Currenty measures 2.86v. As mentioned above, will investigate further and advise in a bit if I find anything.

3) The power on order chart on sheet # 3 of the schematics will be logical to follow.

Will work through this and see what I can find, but the 2 lines above that don't match the working board seem like likely candidates?

[mon2]

Re: MacBook Pro A1278 - No charger light, no PPBUS_G3H, SMC_BC_ACOK short when powere

OK. PPBUS_G3H is still a suspect when powered by your external power supply only.

1) Confirm that you have PP3V42_G3H_REG with ONLY the external power adapter (your BY cable should be fine).

2) See post #2 of this thread and review the voltage @ CHGR_ACIN.

Based on the non-existent PPBUS_G3H with the adapter only case, U7000 is not operating properly - for some reason.

Also, be sure that U7000 is being powered via

PP5V1_CHGR_VDDP
PP5V1_CHGR_VDD
PPCHGR_DCIN

3) The power on order chart on sheet # 3 of the schematics will be logical to follow.