(347) 552-2258 [email protected]

820-3437 No green light

Japtastic

Japtastic

New member
So I'm now on my 5th successful board repair. 1 easy and the rest have been hard but I'm making progress and confidence is building.

So this board is liquid damaged.

There was a short on PP3V42. There were also shorts when testing pins on U7100. Rookie mistake but I didn't note down the pins that showed a short but believe they were Pins 17+18 and 27+28 and possibly one more.

I tested DCIN on the DCIN board before doing any work and it was a steady 14.4v.

I couldn't see any obvious damage around the board so I removed U7100 but the short persisted so I injected 3.3v to see what got hot. I only had the supply on for 5-10 seconds and I could smell something bad so I turned it off and re-inspected the board. Still no obvious damage to anything but on retesting PP3V42, the short had gone and so had any shorts that were on the pins around U7100.

I put a brand new U7100 on and tested again but now DCIN on the DCIN board is unsteady and flicks between 0-3v and then gives up after 10-20 seconds. I checked U7100 and reflowed to make sure it was good. I have taken off U7100 again and a steady 14.4v returns.

Just tested Pin3 on U7100 and it's 3.8v. This chip is currently off the board.

Resistance between 17+18 is 3.7ohm

Resistance between 27+28 is 20ohm

I'm stuck with what to do next...
 
larossmann

larossmann

Administrator
Staff member
PP3V42_G3H is the first supply needed for anything to work. What is the resistance to ground on PP3V42_G3H? What voltage do you get on pins 6 & 8 of U7090?
 
Japtastic

Japtastic

New member
U7100 is still off the board but...

Resistance to ground on PP3V42_G3H on 2MΩ mode = .445

I don't want to second guess anything so I shall now put back U7100 to test U7090 voltages of pin 6 and 8? Even when DCIN is all over the place with U7100 back on?
 
2informaticos

2informaticos

Administrator
Staff member
You don't need U7100 to check U7090 voltages...
Do you get PPDCIN_G3H_ISOL?
Check R7005, D7005 and resistance to ground after it.
Seems that charger detects leakage and gets in protection mode.
 
Japtastic

Japtastic

New member
PPDCIN_G3H_ISOL is present at a solid 14.4v

R7005 tests fine at 10ohm
D7005 Pin 1 = 0.08v Pin 2 = 14.4v Pin 3 = 14.4v

Resistance to ground after these components is around 150k ohm tested at all points they connect to.
 
2informaticos

2informaticos

Administrator
Staff member
Check voltages at U7090.
Be aware at corroded traces.
Change it, if no other components are damaged around...
 
Japtastic

Japtastic

New member
Didn't see your message until this morning.

U7090
Pin1 = 1.23v
Pin2 = 3.4v
Pin3 = 6.7v
Pin4 = 3.2v
Pin5 = GND
Pin6 = 14.4v
Pin7 = N/A
Pin8 = 14.4v

All tested from the pins of U7090

Can't see any broken or corroded traces around there.

Looks ok, right?

Edit: Realising that PP3V42 is back without U7100 on the board.
 
Last edited:
Japtastic

Japtastic

New member
Ok, brand new, out of the packet U7100 but back to DCIN at the DCIN board pulsing between 0-3/6v then gives up after 10 seconds or so. No PPBUS_G3H.
 
Last edited:
Japtastic

Japtastic

New member
Thanks for all your help. Removed Q7130

R7120 now OL

R7150 now 30 ohm to ground.

DCIN now 14.4v Solid.

PPBUS_G3H 0.1V Solid.

PP3V42_G3H 3.4v Solid.
 
2informaticos

2informaticos

Administrator
Staff member
Remove F7140 and let see where the low value remains; pin2 I bet...
If yes, check if any secondary coil has the same value to ground.
 
Japtastic

Japtastic

New member
Yes you are correct.

Pin1 is 3.3/3.5v
Pin 2 is 0.08v

L3095: Pin1+2 = 0.08v

Both L3095 and Pin 2 of F7140 are 144 Ohm to ground.
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
144 should be good on PPBUS_G3H, when F7140 is closed.
You told us something about 30ohms before...
I expected diode scale measurement after remove F7140, not voltages.
However, check if Q3080 is shorted.
 
You must log in or register to reply here.
Top