Dell Latitude 7390 mb:DDA30 LA-F292P - nie widzi zasilacza

matic napisal/-a:

pawel1978 napisal/-a:I'm not sure where to check the forward and reverse voltage..

Forward voltage = Red probe of multimeter to the anode pin of diode and black probe to the cathode pin of diode.
Reverse voltage = Red probe of multimeter to the cathode pin of diode and black probe to the anode pin of diode.
So you already did it.

pawel1978 napisal/-a:PD1202 - multimeter measurement in diode mode - no conduction in one direction

So the reverse voltage is out of range of multimeter.

pawel1978 napisal/-a:reading 253 in the other direction.

That's the forward voltage, which means 0.253V

pawel1978 napisal/-a:pads under PQ 1203
1-19,5V
4-19,5V
8-19,5V

Are these measurements correct?
If the voltage on pad 8 is 19.5V, I expect the voltage 19.247V on pad 1 on the place of these transistor.

I misunderstood about diode measurements - I thought it was about measuring voltages to ground on a soldered diode


So I did the pad measurements again under pq1203.

no pd1202 diode

1-0V
4-0V
8-19.8V

with diode d1203

1-19.5V
4-19.5V
8-19.8V

pawel1978 napisal/-a:with diode d1203
1-19.5V
4-19.5V
8-19.8V

These voltages seems better.
Solder the transistor PQ1203 back to its place and remeasure the voltages to ground on pins 1, 4, 8 of this transistor.

matic napisal/-a:These voltages seems better.
Solder the transistor PQ1203 back to its place and remeasure the voltages to ground on pins 1, 4, 8 of this transistor.

After soldering pq1203 - the measurement comes out identical

1-19.5V
4-19.5V
8-19.8V

Perform the following measurements with the power supply connected to the port JUSBC1:
- Remeasure the voltages to ground on pins 1, 2, 4 of chip PU1202.
- Measure the voltages to ground on pins 1, 2 of transistors PQ1204, PQ1205.
- Measure the voltages to ground on pins 3, 5 of transistor PQ1207.

Transistors PQ1204, PQ1205 pin count:

matic napisal/-a:Perform the following measurements with the power supply connected to the port JUSBC1:
- Remeasure the voltages to ground on pins 1, 2, 4 of chip PU1202.
- Measure the voltages to ground on pins 1, 2 of transistors PQ1204, PQ1205.
- Measure the voltages to ground on pins 3, 5 of transistor PQ1207.

Transistors PQ1204, PQ1205 pin count:
[ Obrazek ]

PU1202
1-3,3V
2-2,26V
4-3,32V

PQ1204
1-19,5V
2-4,83V

PQ1205
1-3,29V
2-0V

PQ1207
3-19,4V
5-0V

Measure the voltages to ground on pins 1, 2, 3, 4, 8, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 31, 32 of charger chip PU901 with the power supply + battery connected.

matic napisal/-a:Measure the voltages to ground on pins 1, 2, 3, 4, 8, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 31, 32 of charger chip PU901 with the power supply + battery connected.

PU901:
1 - 7,45V
2- 7,45V
3- 7,45V
4- 4,78V
8- 5,08V
12- 4,78V
14- 0v
15- 0v
16- 19,5V
17- 19,65V
18- 5,09V
19- 3,51V
21- 0V
22- 0V
23- 0V
24- 0V
25- 0V
31- 7,45V
32- 0V

Check the resistors PR909, PR910. Both are the same (2Ω/1%, package 0603). If they are damaged, you can also use the value 2.2Ω/5% without any problem, because it's more standard.

matic napisal/-a:Check the resistors PR909, PR910. Both are the same (2Ω/1%, package 0603). If they are damaged, you can also use the value 2.2Ω/5% without any problem, because it's more standard.

Both resistors replaced - first had 2.4 kohm, second 0.7 kohm .. I put exactly 2 ohm 1%. After connecting the battery and the power supply in the bios, the message - power supply not connected. Interestingly, both resistors changed their resistance to 0.7 kohm - they were damaged

Measure the resistances to ground on pins 14, 15 of charger chip PU901.

Sprawdź jeszcze jaką ma rezystancję PR916.
U mnie również był on uszkodzony, razem z PU901 na porownywalnej płycie głównej.

matic napisal/-a:Measure the resistances to ground on pins 14, 15 of charger chip PU901.

p.14 - 3,5ohm
p.15 - 1,7ohm

PR916 - 2ohm

The charger chip PU901 (ISL9538H) is definitely damaged and needs to be replaced.

matic napisal/-a:The charger chip PU901 (ISL9538H) is definitely damaged and needs to be replaced.

PU901 replaced. Unfortunately, both resistors still fail when trying to start. This time, in addition, the laptop does not respond to the power button
PU901:
1 - 0V
2- 0V
3- 0V
4- 4,92V
8- 5,23V
12- 4,91V
14- 0,01v
15- 0v
16- 19,5V
17- 19,65V
18- 5,23V
19- 3,37V
21- 0V
22- 0V
23- 0V
24- 0V
25- 0V
31- 0,06V
32- 0V



I was sure that after the pu901 was replaced and the resistors were replaced, the topic would be closed. So I put the whole thing together with the battery and only tried to turn it on .. maybe it's the battery that damages the charging system? As the notebook was still working, it had the status in bios excelent - it is the original Dell

- Remeasure the resistances to ground on pins 14, 15 of charger chip.
- Than remove the capacitors PC926, PC927 from the board and remeasure the resistances on pins 14, 15.

matic napisal/-a:- Remeasure the resistances to ground on pins 14, 15 of charger chip.
- Than remove the capacitors PC926, PC927 from the board and remeasure the resistances on pins 14, 15.

p.14 - 3,3ohm
p.15 - 1,1ohm

without pc926 and PC927

p.14 - 3,3ohm (there is a short circuit on the pads after pc927)
p.15 - 116ohm

damaged resistors pr909,910 are also desoldered

Replace the charger chip again and remeasure the resistances to ground on pins 14, 15 before connecting the power supply or battery to the board.

Usunąłeś tlenki (papier 2000) i pobieliłeś PU901 przed wlutem? Czasami jest taka oksyda, że 1-2 nóżek nie wlutujesz i można nawet CPU ubić.

matic napisal/-a:Replace the charger chip again and remeasure the resistances to ground on pins 14, 15 before connecting the power supply or battery to the board.

New chip solderred - resistance to ground od pin 14 and 15 is 140kohm.

It seems to me that this time and earlier the system was soldered correctly .. but on the other hand, anything can happen.

edit: The laptop works as before The power supply is detected and the battery is charging correctly. Thank you Matic