820-3462 no green light after U7000/Q7080 replacement

Outofwhack

Member
Customers board not turning on. No corrosion evident.
Replaced U7000 and Q7080 and seemed to fix but trackpad cursor had jerkiness.
Very quickly went bad again.

The 68k ohm sparkitecture resistor was not 68kohm so I replaced it with 68kohm and some changes occurred.
Green light would come on momentarily but then extinguish. Sometimes for longer and fans would spin up for a second then stop, then repeat.

Now dead with no green light.
pp3v42 0v (40k ohm to ground so no short)
ppvin_g3h_p3v42g3h 0v
pp18v5_dcin_conn_r 0v
ppdcin_g3h 0.56v
Resistance seen by charger 63kohms
charger no load 0.6v (both my 60W and 85W chargers show same 0.6v)

Is the pp3v42 power supply supposed to start with 0.6v ?
Need help!
 

2informaticos

Administrator
Staff member
Did you test with fake charger, or lab PSU?
Post Q6910 voltages.
I bet for input leakage detected by charger.
Check D6910.
Post R7180/81 and R7185/86 values; measured onboard, ohm scale.
 

Outofwhack

Member
I was using genuine chargers but good idea to try lab psu.
Lab PSU at 16.6v gets orange light and fans did spin but not for long. Now dead again.
Orange light stays on when plug charger

pp3v42 3.4v
ppdcin_s5_chgr 16.42v
chgr_agate_div 15.68 so left side of Q7080 should be conducting yet ppdcin_g3h_drains is 1.77v LOOKS WRONG

Q6910
pin 1,2,3 16.42
pin4 6.73v
pin5,6,7,8 16.42v

D6910 0.74v diode mode
Trust you mean R7080/81 99k/62k
Trust you mean R7085/86 500!!!/330k
With R7085 removed I measured 0.7k on its pads

Question: When powering up is it a common sign to see the odd
bubble or puff of smoke from underneath a component you may have covered in flux or soaked with IPA and not dried out thoroughly enough before powering up? Or is it always a component taking too much current and getting damaged?
 
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Outofwhack

Member
Right away but just found ... I put a new R7085 in and Im now getting fanspin but only with lab PSU. 2 genuine charger 60W/85W wont start it.
Shall I get those voltage when on genuine charger without fanspin?
 

Outofwhack

Member
Current situation is I get fanspin with LAB PSU only. On connection initially get green light but quickly changes to orange.
ppbus_g3h has an 800mV ripple but does average 12.6v

U7000 voltages when fanspin with Lab PSU.
PIn voltage
1 0
2 15.8
3 3.8
9 0
12 3.4
13 3.4
14 3.4
15 0
17 12.5
19 5.5
20 5.5
27 0.3
 

2informaticos

Administrator
Staff member
"27 0.3"
Are you sure about this?
If yes, change R7022; also check R7021.
Be sure C7021/22 not shorted to ground.
 

Outofwhack

Member
Yes double checked the 0.3v on pin 27

I changed R7021/22 yesterday as 7021 looked ugly before (lumpy) so if they have gone wrong there is something else causing it.
 

Outofwhack

Member
I took off all the feedback components U7000 and C7020/21/22 and R7021/22 and found one trace had 2.7kohm to ground. All reassembled, test tomorrow, need sleep. Thanks for your help.
 
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