820-2879 Green light no start no orange light

rlowe215

Member
Im working on an really old 820-2879. No sign of water damage. Have green light but PPBUS_G3H
starting at 6v and drops to about 1.5v. When battery connected its 12.8V and no drop but still no start and battery doesn't charge.

Dont have any working board of this old crap to compare to.

F7040 in diode mode shows 0.447V
 

rlowe215

Member
L7220 5.08 kohm
L7260 22.5 kohm

U7200 pin 8 dont get a value just counting up starting from 320 kohm
pin 17 dont get a value just counting up
 
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2informaticos

Administrator
Staff member
Post resistance value between pins 17/18 and 27/28 on U7000.
Also post voltages at pins 2, 19, 20, 1, 26, 9, 15...
 

rlowe215

Member
Now Im back from holliday =)

Resistance 17/18 3.2ohm
27/28 20.5ohm

voltage pin1 14.81v
pin2 16.22
pin19 5.15
pin20 5.15
pin21 0v
pin26 15.74
pin9 0.032v
pin12 3.41
 

dukefawks

Administrator
Problem around the TPS51125. Check for corrosion and damage. Check both coils for short to GND. If all good then replace the TPS.
 

rlowe215

Member
replaced TPS and also c7220 and c7220.
still drops from 1.5v slowly to =´0

now measuring U7200 in diode mode

pin1 0.546
2 0.695
3 0.656
4 0.622
5 0.013
6 0.549

7 0.472
8 0.625
9 0.571
10 0.0
11 0.122
12 0.436

13 0.702
14 0.665
15 0.0
16 0.449
17 0.489
18 0.496

19 0.443
20 0425
21 0.831
22 0.594
23 0.441
24 0.431

changed r7269 and r7270 and now pin 5 0.671v
 
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dukefawks

Administrator
Monitor PPBUS and plug in adapter, the voltage should spike up to 12.xV and then drop down. This indicates the ISL6259 is detecting an over current situation. But first need to know if the voltage comes up at all.
 

rlowe215

Member
when I not touched the board for some time it will spike up to 12.4 and then drop down but now it just go up to 1.6v and then slowly down. Just have a multimeter to test with. It measures about 0.8V long time after disconnecting charger.
 

rlowe215

Member
Ok now Im back and so are the green light =) NO 3V3_S5 with battery and AC power. PBUS not dropping with battery in place 12.6V. No orange light.
 

rlowe215

Member
measured u7200 with battery and ac power
1 0v
2 0v
3 2.0v
4 3.32v
5 0v
6 0,725v
7 0v
8 3.2v
9 4.5v
10 0v
11 0v
12 0v
13 3,379v
14 2.0v
15 0v
16 12.59v
17 4.98v
18 0.062v
19 0v
20 0v
21 0v
22 4.51v
23 0v
24 0v

suddenly pp3v3_s5 was shorted to ground so tried to insert 3.3v to the rail. After a wile the short was gone and g3h was 12.6. Green and orange light when plugged in battery and ac. Tried to power on and fan spinned for one second. After this everything was back where I started with g3h dropping and no orange light. pp3v3_S5 only 0.063V and in diode mode 0.143V.

Another edit =) Changed U7200 once again and now g3h stable at 12.6 and battery charging. quarter fan spin. But pp3v3_s5 are 4.026V! Cant really understand what happening with this board =(
 
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dukefawks

Administrator
Yeah L7220 sorry. 4V is no good and means either bad soldering on U7200 or dead U7200 or bad Q7220 or something corroded around U7200. If replacing anything replace U7200 and Q7220 at the same time.
 

rlowe215

Member
tryed change U7200 and Q7220 at the same time and still 4.02V =) Cant understand why.

voltages U7200
pin1 0
2 0
3 1.189
4 4.0
5 2.04
6 0.777
7 4,0
8 4.0
9 8,28
10 4
11 4
12 0.04
13 3.378
14 1.989
15 0
16 12.6
17 4.95
18 0.062
19 0
20 0
21 0
22. 4.49
23 0
24 0

everything seems messed up
 
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