Shorted C3201 w/ R3032 on 820-00281

[iMuhtaseb]

Hello,

First, I would like to thank everybody here and how grateful I am of being here and posting here my first thread.

I'm new to fixing MacBooks in micro soldering level and I'm trying my best on learning and upping my skills.

So here it goes;

I received couple of days ago a 820-00281 that turns on normally but w/ high fan spin and slowness. I did the visual inspection and found liquid residue near U3500, U5850 and a bit near U3906.

I cleaned it properly and found C5850 damaged and Pin #1 on U5850 also corroded so it wasn't getting the proper power.. after removing U5850 and cleaning it and resoldering it w/ a good cap the computer posted with normal fan spin and normal speed.

One thing I noticed after all this is one of the USB-C ports was not working properly; it was charging the MacBook Pro but plugging in a dongle w/ USB flash did not work.. they seemed to have not get power..

Now here's the funny part

I was measuring voltages around the board to see what's causing the issue and I've mistakenly shorted C3201 w/ R3032 (I know, epic), a small spark came and computer got stuck at 5v after this.. and I have no idea what had gone wrong or where to start from.

PP20V_USBC_XB_VBUS is present at 5v
PP3V3_UPC_XB_LDO is not present and testing C3208 pin 1 is shorted to ground



I will happily give any information required

And I am most grateful for any help offered

[piernov]

Re: Shorted C3201 w/ R3032 on 820-00281

Well then that most likely killed U3200 without surprise, and could have also damaged U3100 and U3500.

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

Thank you so much for your reply

I have couple of CD3215 I can replace U3100 and U3200 but I don't have a replacement for U5850 (TMP461), should I go and try replace the two CD3215s only??

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

Hello!

New steps and informations have surfaced:

I replaced both U3200 and U3100 successfully with U3500 (because it was shorted); exactly what @piernov expected, thank you.

But still the computer is stuck on 5v

LDO 3.3v is present
PP3V3_G3H is present now as well

What I have noticed is there is a short on:
R3033, UPC_XA_HPD_RX,
R3034, UPC_XB_HPD_RX

And I'm quite stuck here I really don't know what do..

Help?

THANKS

[piernov]

Re: Shorted C3201 w/ R3032 on 820-00281

It seems like both of these lines connect to SMC_RESET_L through R3035 and R3036. So you can disconnect these resistors (just shift them away from one pad) to see if that clears the short to ground.

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

The thing is R3036 and R3035 are no stuff and they're not on the board.. I thought I might have knocked them out by mistake but I looked up online on and iFixit images reassured me that these resistors are not on board (image attached).

[piernov]

Re: Shorted C3201 w/ R3032 on 820-00281

Ok, they are not no stuff in the schematics (and no BOM option either) so not sure.
R3033 and R3034 are populated instead maybe?
Are UPC_TA_HPD_RX and UPC_TB_HPD_RX shorted to ground as well?

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

Sorry if I didn't make this clear from before; yes R3033 and R3034 are populated.

When I remove R3033 boom short is gone and when I remove R3034 short is gone as well.. I tried installing new resistors, the short comes back again..

No short on UPC_TA_HPD_RX or UPC_TB_HPD_RX..

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

One thing I've tried, I have no idea if it helps or not is replacing those 0ohms resistors with 100k resistors and it stopped the short but have not resolved the issue still stuck at 5v.

[piernov]

Re: Shorted C3201 w/ R3032 on 820-00281

Then they are probably meant to be shorted to ground for some reason and this is a wrong lead.
Anyway, measure voltage and diode mode to ground on all 4 LDOs of each CD3215 (with Magsafe connected to corresponding port).

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

PP3V3_UPC_XB_LDO 3.3v, diode 1.677
PP3V3_UPC_XA_LDO, 3.3v, diode 0.523
PP3V3_UPC_TA_LDO, 3.3v, diode 0.525
PP3V3_UPC_TB_LDO, 3.3v, diode 2.355

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

Couple of things I've noticed:

When I plug the charger to the other side of the board, other side of CD3215 (unharmed ones), it cycle every 5 seconds.. the amp meter turns on for 5 seconds with 5v then restarts.. I have no idea if this helps or not..

The other thing I've noticed as I'm trying to gather as much information as possible,

I used logi's boot sequence for CD3215 to measure some components:

5v appear on PP20V_USBC_XB_VBUS when I plug the charger on one port only, I have not idea if this is the usual or not..

PP20V_USBC_XB_VBUS appear on one USB-C port as I mentioned:
PP3V3_UPC_XB_LDO is 3.3v
PP1V8_UPC_XB_LDOA is 1.8v
PP1V8_UPC_XB_LDOD is 0.001v
PP1V1_UPC_XB_LDO_BMC is 1.1v
PPDCIN_G3H is 5v
TBA_VDDA is 5v
PM_EN_P3V3_G3H is 5v
PP3V3_G3H is 3.3v
PP1V2_S5_SMC_VDDC is 1.2v
PP3V0_S5_AVREF_SMC is 3.0v
SMBUS_SMC_4_G3H_SCL is 3.4v
SMBUS_SMC_4_G3H_SDA is 3.4v
USBC_XB_CC1 is 0.8v
USBC_XB_CC2 is 0.00v


Hope this helps!

[piernov]

Re: Shorted C3201 w/ R3032 on 820-00281

There are 4 LDOs for each CD3215

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

Please, forgive my ignorance.

I had no idea.

I hope I got it right this time.

U3200
PP3V3_UPC_XB_LDO 3.3v
PP1V1_UPC_XB_LDO_BMC 1.1v
PP1V8_UPC_XB_LDOA 1.8v
PP1V8_UPC_XB_LDOD 0.001v (tried both ports)

U3100
PP3V3_UPC_XA_LDO 3.3v
PP1V1_UPC_XA_LDO_BMC 0.00v (tried both ports)
PP1V8_UPC_XA_LDOA 1.8v
PP1V8_UPC_XA_LDOD 1.8v

UB300
PP3V3_UPC_TA_LDO 3.3v
PP1V1_UPC_TA_LDO_BMC 1.1v
PP1V8_UPC_TA_LDOA 1.8v
PP1V8_UPC_TA_LDOD 1.8v

UB400
PP3V3_UPC_TB_LDO 3.3v
PP1V1_UPC_TB_LDO_BMC 1.1v
PP1V8_UPC_TB_LDOA 1.8v
PP1V8_UPC_TB_LDOD 1.8v

I truly appreciate your help.

[piernov]

Re: Shorted C3201 w/ R3032 on 820-00281

What about diode mode to ground?

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

My apologizes,

It slipped my mind to gather diode info

U3200
PP3V3_UPC_XB_LDO 3.3v, diode mode 0.528
PP1V1_UPC_XB_LDO_BMC 1.1v, diode mode 0.534
PP1V8_UPC_XB_LDOA 1.8v, diode mode 0.541
PP1V8_UPC_XB_LDOD 0.001v (tried both ports), , diode mode OL

U3100
PP3V3_UPC_XA_LDO 3.3v, diode mode 0.527
PP1V1_UPC_XA_LDO_BMC 0.00v (tried both ports), diode mode 0.541
PP1V8_UPC_XA_LDOA 1.8v, diode mode 0.546
PP1V8_UPC_XA_LDOD 1.8v, diode mode 0.507

UB300
PP3V3_UPC_TA_LDO 3.3v, diode mode 0.530
PP1V1_UPC_TA_LDO_BMC 1.1v, diode mode 0.537
PP1V8_UPC_TA_LDOA 1.8v, diode mode 0.540
PP1V8_UPC_TA_LDOD 1.8v, diode mode 0.503

UB400
PP3V3_UPC_TB_LDO 3.3v, diode mode 0.530
PP1V1_UPC_TB_LDO_BMC 1.1v, diode mode 0.536
PP1V8_UPC_TB_LDOA 1.8v, diode mode 0.540
PP1V8_UPC_TB_LDOD 1.8v, diode mode 0.502

P.s great job on advising Paul Daniels not to mix the RAMs on yesterday's stream. 😊

[piernov]

Re: Shorted C3201 w/ R3032 on 820-00281

U3200
PP1V8_UPC_XB_LDOD 0.001v (tried both ports), , diode mode OL

Look like U3200 is not soldered properly or some of its pads are damaged.

[iMuhtaseb]

Re: Shorted C3201 w/ R3032 on 820-00281

U3200 was removed and reballed properly and amp meter reads 20v now.

The computer posts successfully.

I cannot thank you enough, piernov.