can you help me with 820-01700-A missing 20v and 12v

[mgjini]

hello all

i have been trying for days to resolve this board 820-01700-A, i have been reading the logiwiki but i still can not find the issue with this board, the board looks clean, and i have been inspecting it and i don't see any water damage or anything like that

https://repair.wiki/index.php?title=...e_view_desktop

on all 4 ports i get 5v i am missing 20v and 12v, i have checked the cd32s like another person was asked here to do so https://www.badcaps.net/forum/showthread.php?t=118994 , red probe on ground and black on the capaictors ub40 ub30 u3100 u3200 and they are giving 0.568v , with power attached i am getting 5v and all the above


I also connected laptop with another macbook and run apple configurator 2 to see if laptop was in dfu mode but the other macbook did not detect the macbook

PPBUS_G3H 0.586v with power attached
PP3v3_G3H_RTC_X 0v
PP3v3_G3H_SOCPMU 0v

PP1V5_UPC_TA_LDO_CORE 0.547v
PP1V5_UPC_TB_LDO_CORE 0.547v
PP1V5_UPC_XA_LDO_CORE 0.538v
PP1V5_UPC_XB_LDO_CORE 0.543V

PP3V3_UPC_TA_LDO 0.514V
PP3V3_UPC_TB_LDO 0.524V
PP3v3_UPC_XA_LDO 0.521V
PP3V3_UPC_XB_LDO 0.520V

Any help i would be grateful

[mon2]

Re: can you help me with 820-01700-A missing 20v and 12v

PPBUS_G3H 0.586v

Rail is likely shorted. Remove the fuse on this rail. Remove all power. Measure the resistance to ground on each side of the removed fuse but on the PCB pads.

Post your measurements.

[mgjini]

Re: can you help me with 820-01700-A missing 20v and 12v

on oms mode black proble on the ground and red on each side of the pads i am getting 73oms on both sides of fuse f7000 , each side of the fuse the probes 0oms, and is shorted

[mon2]

Re: can you help me with 820-01700-A missing 20v and 12v

Remove the fuse at F7000 and measure again.

[mgjini]

Re: can you help me with 820-01700-A missing 20v and 12v

hi the measuruments above was when i removed the fuse f7000, with the fuse back on is short again, diode mode red ground black on each side 0.454v , on ohms mode red on ground black on each side of the fuse 3.265 mΩ

[mon2]

Re: can you help me with 820-01700-A missing 20v and 12v

In post #3 - 73 ohms to ground? Can you confirm?

Is the fuse now removed from the board?

If yes, power up (without this fuse) and check the voltage of the PPBUS_G3H to ground.

[mgjini]

Re: can you help me with 820-01700-A missing 20v and 12v

it is 015.0 ohms to ground on both sides of the pad fuse f7000, i powered it up and measured without fuse and i am gettig 0.126 v ppbus_g3h

[mon2]

Re: can you help me with 820-01700-A missing 20v and 12v

Sorry - forgot that are 2 fuses on this PCB.

Locate and remove F7001 as well.

Then check the resistance again on each side of the fuse pads (either one is ok).

[mgjini]

Re: can you help me with 820-01700-A missing 20v and 12v

hi, sorry for the late replys, i have removed the f7001, and i have 12v on one side and nothing on ppbus_g3h

[mon2]

Re: can you help me with 820-01700-A missing 20v and 12v

Good. Your ISL chip is working.

Remove all power. Check the resistance to ground of the side of the fuse that is shorted.

What is the resistance?

Do you have an adjustable power supply?

[mgjini]

Re: can you help me with 820-01700-A missing 20v and 12v

it says 0.15ohms and yes i have adjustable power supply, i applied some power and the only thing that gets noticed on thermal camera is this chip u6420, after removing this chip now i get 3.45 m ohms one the 12v side and on the ppbus_g3h side i get much higher readings now like 2.56 m ohms and different measurements but all above 1.00 m ohms

[mgjini]

Re: can you help me with 820-01700-A missing 20v and 12v

after removing this chip u6420 and replacing it i now have on both sides 12.26v but still no power i wonder if there is something wrong with isl chip

[mon2]

Re: can you help me with 820-01700-A missing 20v and 12v

No, ISL is fine but it is not being instructed to kick upto 12v6.

See here:

https://boards.rossmanngroup.com/thr...s-12-3v.62475/

Check the SMBUS rails on the ISL chip (SDA / SCL). What are their voltages to ground?

[mgjini]

Re: can you help me with 820-01700-A missing 20v and 12v

Hello there, sorry for not replying earlier, my measurements are same as this guy who posted on rossmangroup, now I am just waiting to see if I can find another MacBook to see again if MacBook is in dfu mode

[mgjini]

Re: can you help me with 820-01700-A missing 20v and 12v

hi i connected macbook with another macbook and it doesn't show on apple configurator 2, so i don't think is in dfu mode

reading on the link you provided

UPC_I2C_INT_L = 0v

i don't know if it is worth mentioning pp3v3_g3h_socpmu 0.328v c7891/92

i don't know if i now should move the cd32 chips as in the forum

[ugamazing]

Re: can you help me with 820-01700-A missing 20v and 12v

You should first confirm the SSDs are not shorted--a common issue with the 01700 and a very common cause of shorted ppbus_g3h.

[mon2]

Re: can you help me with 820-01700-A missing 20v and 12v

Remove all power. Meter in resistance mode.

Measure the resistance to ground of each rail from your post #1.

Post each measurement.