820-02020 5v

[Outofwhack]

Im going around in circles not understanding whether Ive got a CD3217 area problem or a U5200 problem.
No corrosion.

Both ports stay at 5volts and draw a fluctuating 0mA to 300mA but no switch to 20v.
I saw some reduced readings on an LDO of one CD3217 and tried replacing it. I replaced both in the end but still no 20v.


I was getting 12.3v on PPBUS_AON but eventually I noticed every few seconds it would dip a couple of volts. See voltage graph.


I removed fuse F5200 and impedance of downstream cct looked fine.
Under no load regulator side of open fuse PPBUS_AON sat steady at 12.3v
I connected a dummy load of 22ohm to see if it could supply roughly 0.5amp. No! Supply sank to 0.2volts
Changed U5200 but still same.
Continuity of PBUS to CHGR_PBUS_SNS (A3) of U5200 good.
CHGR_AUX_DET is 1.28v .
PP1V8_S2 is 0v when fuse removed. VDDIO1P8 on U5200. Does not need 1.8v to produce 12.3v as seen when dummy load removed.

Guidance appreciated

 

[2informaticos]

"PP1V8_S2 is 0v when fuse removed"
Of course, PPBUS_AON is the mother of all secondary power supplies!

If you get steady 12.3V at C5250, when fuse is removed, your problem should be on secondary side.
You didn't say anything about 3V8_AON; diode mode and voltage.

 

[Outofwhack]

Can we not rule out the secondary side downstream of the F5200 ???? since I connected a 22ohm resistance to the steady 12.3v on C5250 [with F5200 removed] and it sank to 0.2volts.
The regulator could not even drive 0.5amp (expected if a 22ohm resistance is used as load on a 12.3 volt supply).

 

[2informaticos]

Not sure if U5200 accepts that; test on working machine.

Did you replace CD3217 chips with correct donors?
Try reflashing UF260.

Just in case, check resistance (ohm scale) over C5220/60.

 

[Outofwhack]

Tested on working board, removed F5200 added 22ohm load. Same result - Regulator sinks to output 0.2v and no switch to 20v.
So my faulty assumption wasted hours [as usual]. Thx for the question!

DM of faulty board at F5200 is 0.44
CD3217 used correct donors afaik.
3V8_AON 3.8v and smooth, DM 0.11 0.96kohm FWIW
C5220 2.1ohm, C5260 300ohm! cripes thought Id checked that! R5262 had become 300ohm.
Replaced and now all glitches in voltage levels are gone.
No 20volts so will try reflash.

 

[Outofwhack]

Tried UF260 from two donors - no change.

 

[2informaticos]

"DM 0.11"
Are you sure?
That is not good at all.

I had one 02536 with 0.150 aprox; it started each time after injecting 3-3.5V for 20-30s there.
Normal reading is around 0.450 I think.

BTW, red probe at ground, when measuring in diode mode.

 

[Outofwhack]

I confirm 3V8_AON 3.8v steady but diode mode 0.11v red to gnd, 0.96kohm fwiw

L7740/41 dm 0.00 with 2.4ohm to gnd (my donor board has dm 0.02v and 66ohm to gnd)
Although when i inject 1v here the current drain 0.08A achieved indicates 11ohm to gnd and with only 0.08Watt drawn nothing spotted on thermal cam.

 

[2informaticos]

0.110 diode mode reading is too low for 3V8_AON.
Expected reading is between 0.350-0.450 depending on the multimeter used.

OpenBoardData Project

L7740 should be 0.060 aprox in diode mode.
Seems that you have almost short there.
Lift L7740/1 and R770A, then check where the low reading remains.

 

[Outofwhack]

P1V06_S2SW_DRAM has the short. dm 0.00v and 1.4ohms.
Thinking the short could not affect the secondary pmic U7700 I thought I would see if it switches to 20v, answer = no.
So is this short an unrelated problem to the 5v20v switching? or does it rely on ram access?

 

[2informaticos]

SMC controls the USBC power input; and it is now included into CPU.
Not sure if SMC part requires fully working CPU.
But short on DRAM, doesn't mean 100% DRAM itself is the problem.
CPU blocks are connected there too.

 

[Outofwhack]

I removed C7740 to C7747 and C7710 to C7713 and C777M/N short remained.
Then realised that P1V06_S2SW_DRAM feeds back into U7700, CPU U0600 and another 24 caps.

Is it worth removing the 24 further caps? or is it more likely a CPU fault or more likely a U7700 fault?

U7700 lifted, short remains.