A1932 820-01521-A PP3v3_UPC Short

[rotceh_dnih]

Hi all got a head scratcher

A1932 came in booting just with no keyboard or trackpad, I found missing PP3v3_G3S rail on J6700 lead me to what I thought was a short around U3700 "wifi ic" so i removed R5510 and injected voltage 0.5v not seeing anything under thermal camera i stupidly increased voltage to around 2v 3A and still nothing..

Now i have no boot and short on both CC PP3v3_UPC_XA_LDO 8.4Ω & PP3v3_UPC_XB_LDO 2.5Ω, PPDCIN_G3H is 0V regardless of what port i plug into and my voltages are as follows

Port 1 - U3200 5v - 0.148A

Port 2 - U3100 5v - 0.153A

Nether cycles so my best guess atm is both CD32's are dead? any assistance would be greatly appreciated!

Prior to repair I warned my customer of known cpu issues and made a backup so i don't feel to bad just tilted i made things worse.

[rotceh_dnih]

Re: A1932 820-01521-A PP3v3_UPC Short

I've Ordered two new CD3215C00 ic's just waiting on the postman.

However, before I install them, is there anything I should be looking at before I power up?

Pretty sure I still have a short @ pin 1 R5510, but if after CC32 replacement it boots I'm handing it straight back and referring them to someone like Paul Daniels, I'm just worried I caused more damage then what i found :/

Also if anyone has any tips on voltages or basic steps/post formatting I may have missed or not posted that would help with diagnostics I'm very open to hearing you out and learning!

[mon2]

Re: A1932 820-01521-A PP3v3_UPC Short

What is the voltage to ground of PP3v3_G3H_RTC?

Check this webpage about your case:

https://repair.wiki/w/A1932_2018_-_2019_MacBook_Air

[rotceh_dnih]

Re: A1932 820-01521-A PP3v3_UPC Short

PP3v3_G3H_RTC = 3.291V

I replaced both the CC32 ic's and now its back to 20v and seems like its charging and somewhat booting as i have fanspin again but no image

I checked its not in dfu mode then ran the thermal cam over the board again and seen U8210 is hot so i lifted it and i still have a short on pin 5/6 PP3v3_G3S

I'll lift R5510 again and see its its really on the PP3v3_G3S_WLANBT line & read through the repair wiki and report back.

Also has anyone got any good suggestions for a new lab power supply ? i need something that can do 5-10A @ 0.5v-1v as my current supply is limited to 3A and only gets there above 2V..

[mon2]

Re: A1932 820-01521-A PP3v3_UPC Short

We use the TS-30A Short Killer product from Phone fix on AliExpress. It can spike out 30A and we dial up 0v8 on the voltage. Works well to locate shorted caps.

[rotceh_dnih]

Re: A1932 820-01521-A PP3v3_UPC Short

Ordered one thank you very much!

Lifted R5110, Short still on pin 1. after some thermal imaging @ low voltage limited current i didn't see anything so suspected U3700, Lifted U3700 WIFI/BT IC and my short from PP3v3_G3S is now gone however its still not booting though i get 20v and what seems to be normal booting/charging current.

all voltages around U7800 appear normal without cycling and as per the wiki these rails check out

PP5v_G3S - 5v & high resistance 10K+
PP3v3_G3S - 3.3v & high resistance 10K+
PP1v8_G3S - 1.8v & high resistance 10K+
PP3v_G3H - 3v & high resistance 10K+

then i get to PPBUS_G3H

PPBUS_G3H - 9.7v 53K+ this is so very wrong.. U7000?

[mon2]

Re: A1932 820-01521-A PP3v3_UPC Short

Remove the fuse on PPBUS_G3H.

Power up again. What is the voltage to ground of PPBUS_G3H from the producer side (ISL)?

[rotceh_dnih]

Re: A1932 820-01521-A PP3v3_UPC Short

Sorry that reading was with battery connected and it must have been alittle flat as its up to 12v now and 12.65v without battery connected and 12.65V with a know good battery.