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N

Neil250

Member
PP18V5_DCIN_FUSE measured at PAD 1 F6905 is 0V

Diode mode
F6905: 0V on both pads (shorted)
R6990: shorted on both sides

R6990: 47 Ohms

? Short somewhere on the PPDCIN_G3H rail

I remember the warning not to inject voltage ever into anything that supplies PPBUS_G3H unless high side mosfets are checked first.

How do you begin to isolate a short on a rail with so many points where the short could be?

Start checking voltages at U7000?
 
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2informaticos

2informaticos

Administrator
Staff member
Are you sure about that short?
Did you disconnect charger on measured on diode mode?

Did you try known good DCIN board?
 
N

Neil250

Member
DCIN Board is good
Charger disconnected for measurements on diode mode

Resistance to ground checks

C6905
1: 1.6 O
2: .5 O (GND)

F6905
1: 1.5 O
2: .1.5 O

Q5310
4: 1.5 O

R5311
R: 100K
PIN 1: 1.5 O
PIN 2: 99.8 kO

R7085:
1: 1.5 O
2: 393 kO

D7005
1: 1.5 O
2: 1.5 O


I did note a hole in the top of T4000 (pic attached) and damage to L7760
 

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N

Neil250

Member
OK.
Charger disconnected

C6905
1: Short
2: Short (GND)

F6905 (C6905 also off)
1: OL
2: Short

R6990
PIN 1: short
PIN 2: 0.56 V
 
N

Neil250

Member
Diode mode to ground

L7030: no short
1: 0.449V
2: 0.449V
3: OL

D6990
1: 0.445 V
2: SHORT
3: 0.306V

D7005
1:short
2:short
3: 0.242V


R7085
1: Short
2:OL

C7085
1: Short
2:OL

R7010
1: Short

R7011
1:.535V

R7020
1: 0.645V
2:0./645 V

Q7080
5: SHORT

Q7030
1,2,3: 0.448V
4: 0.913 V
5: 0.655 V

U7000
1: 0.658 V
2: 0.261 V
3: 0.535V
26: 0.657 V
27: 0.652 V
28: 0.637 V

R 27-28: 20.3 O

R7021
1: 0.637 V

R7022
1: 0.654 V

Q5310

4: SHORT
5: OL

R5311: 100K
1: SHORT
2: OL
 
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2informaticos

2informaticos

Administrator
Staff member
Why do you like so much to measure same line in various points???
One value is sufficient; unless the trace is broken.

Looks like you have a short inside copper layers.
No cap, or active component remains directly connected to ground on PPDCIN_G3H line.

Just in case, remove Q7080 and check again.
 
2informaticos

2informaticos

Administrator
Staff member
Sometime possible.
You must cuttoff that line in few points.
The idea is to isolate the short part and bypass it with an wire.
 
N

Neil250

Member
Q7080 removed

Still short to ground tested at R7085 PIN 1

When F6905 removed
PIN 1: OL
PIN 2: SHORT

So short is after F6905 (not in dc in board or J6900) and Not in Q7080 or in reverse current protection part of circuit?

Remove R7010 and check if short remains on PIN 1 or PIN 2?
 
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2informaticos

2informaticos

Administrator
Staff member
How can a resistor (high ohm value) generate a short???

I faced with similar problem years ago, with old 2879 board; solved with method above mentioned.
 
N

Neil250

Member
Here is my logic:

As you said, I have to cut off the PPDCIN_G3H at various points, I chose R7010

Remove R7010 and check if short remains on PIN 1 or PIN 2?

If R7010 is removed AND


PIN 2 Diode mode to ground is SHORT then the short is somewhere in the line after that resistor

I know my logic must be screwed up somehow.
 
2informaticos

2informaticos

Administrator
Staff member
That logic has NO sense at all.

You actually don't and never will have short on pin 2/R7010.
If you have short on pin 1 (0 ohm), how can 0+30K generate that short???

Please understand, the goal of this forum is to help online on the repair process.
If you need training course, contact Rossmann's staff.

Follow PPDCIN_G3H trace and cutt it off in few points.
Not close to any component terminal; just in the middle of some of its sections.
Post pictures of what you did.
And specify, where the short remained.
 
N

Neil250

Member
Follow PPDCIN_G3H trace and cutt it off in few points.

By "cut it off" do you mean actually disrupt the trace by breaking the physical copper trace on the board ?
 
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2informaticos

2informaticos

Administrator
Staff member
Of course, you need to isolate the trace part shorted to ground.
At least two points to cuttoff PPDCIN_G3H.
You'll probably need to do it in more points, untill find the way to isolate the short.

First of all, try to isolate Q7080 input.
This MOSFET must be soldered in its place.
The other components can be soldered in just one pin and run a wire to a common point for the other pin of them all; including F6905.
 
N

Neil250

Member
OK

Interrupted trace to R6990 PIN 1
Short before break, no short after break

Interrupted trace from R5311 PIN 1 to PIN 4 Q5310
Now no short at PIN 1
Short at PIN 4

Short somewhere in DC sense in circuit?

Q5310 PIN 2 is also short to ground

Will continue to test
 
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