La-c881p

[riki_22]

Re: La-c881p

Remove battery. Connect adapter.

1) voltage on pin 6 (acdet; pu300) ?
2) voltage on pin 17 (pu300) ?
3) voltage on pin 1, pl300? Pin 2, pl300?
4) pl301, pin 1? Pin 2?
5) confirm the nearby diodes are ok (power removed, meter in diode mode). Should conduct in one direction, block in the other).
6) pin 15 voltage of pu300 with adapter only?

Pu300 with Adapter
P6 3.2v
P17 0v
P15 1.72v

Pl301 p1 3.12 and P2 3.12
Pl300 p1 19.6 and P2 19.6

The diode work ok not shortly

[riki_22]

Re: La-c881p

Voltage from battery goes through PQ305 & PQ303 body diode to reach VCC pin of charger IC.
PD300 should be replaced first, not much point troubleshooting further if parts are missing.

You need a Schottky diode of at least 30V reverse voltage and 30mA forward current and the same package. So yes RB501V-40 should be good instead of SDMK0340L

Note that it's possible there is a secondary problem and PD300 will burn again, so keep a few aside in case. It's also possible it's the only problem and replacing it will solve it.

Hi i Just try the RB501-V40 but mainboard not Power with Adapter what measurements can i take to find the problem?
rb501-v40 for me is not good because it does not turn on even with the battery alone

[mon2]

Re: La-c881p

You have a fault at pr300, current sense resistor. Review the voltage before and after this component. It must be very close to the adapter in voltage. This part may need to be replaced.

Consider to carefully remove pr303 and pr304 then check the voltage through the current sense resistor again. Does the voltage reading match the adapter voltage? If not, pr300 is damaged.

See and review attached partial schematic.

@ 1 - voltage must match the adapter DCIN value.

@ 4 - voltage should be very close to the adapter DCIN value. From your post, this voltage @ 4 is 3v12 ?? If yes, then the charger IC is noting a very large voltage drop and shutting this component down. That is, approx 19VIN is dropping to 3v12 which is too much of a load for this switching IC to enable.

You can remove the above mentioned resistors and then check again @1 and @ 4.

Also inspect this SMD current sense resistor for damage. Power all down and check the resistance from @1 and @4 points.

[riki_22]

Re: La-c881p

You have a fault at pr300, current sense resistor. Review the voltage before and after this component. It must be very close to the adapter in voltage. This part may need to be replaced.

Consider to carefully remove pr303 and pr304 then check the voltage through the current sense resistor again. Does the voltage reading match the adapter voltage? If not, pr300 is damaged.

See and review attached partial schematic.

@ 1 - voltage must match the adapter DCIN value.

@ 4 - voltage should be very close to the adapter DCIN value. From your post, this voltage @ 4 is 3v12 ?? If yes, then the charger IC is noting a very large voltage drop and shutting this component down. That is, approx 19VIN is dropping to 3v12 which is too much of a load for this switching IC to enable.

You can remove the above mentioned resistors and then check again @1 and @ 4.

Also inspect this SMD current sense resistor for damage. Power all down and check the resistance from @1 and @4 points.

i checked the voltage at the end of pr300 and they are the same as the power supply input, i can't find pr303 and pr304 to verify what you say

[Sephir0th]

Re: La-c881p

Right, PR303 and PR304 are Just Pads, No component there. but i don't think the issue is there. Never Heard about a failed Current Resistor.

I believe we need a complete measurement of PU300 Résistance to GND, and Voltage (Only Battery/Only Adapter/both present) to See what is going on there.

A complete D-S-G Résistance measurement of PQ305 could be also helpful

[mon2]

Re: La-c881p

i checked the voltage at the end of pr300 and they are the same as the power supply input, i can't find pr303 and pr304 to verify what you say

Pl300 p1 3.12 and P2 3.12

Are these readings correct ?

PL300 (P1) should be the same voltage value AFTER PR300. Confirm it.

Also, see attached for the resistor locations.

[riki_22]

Re: La-c881p

Pl300 p1 3.12 and P2 3.12

Are these readings correct ?

PL300 (P1) should be the same voltage value AFTER PR300. Confirm it.

sorry friend
I had inverted the measurements between pl 300 and pl301.
with certainty the correct measurements are:
in pl301 p1 3.2V and p2 3.2V
in pl300 p1 19.6V and p2 19.6V

[riki_22]

Re: La-c881p

Right, PR303 and PR304 are Just Pads, No component there. but i don't think the issue is there. Never Heard about a failed Current Resistor.

I believe we need a complete measurement of PU300 Résistance to GND, and Voltage (Only Battery/Only Adapter/both present) to See what is going on there.

A complete D-S-G Résistance measurement of PQ305 could be also helpful

making all these measurements will take me time, I just wanted to remind you that instead of pd300 I didn't put anything, and I wanted to clarify that I tried to make the bridge and in pd300 it turns on but as soon as I insert the battery the power supply is shorted, so according to me I have to find the right component to install in pd300. i have already tried RB501V-40 but with this it does not turn on.

[Sephir0th]

Re: La-c881p

I know what you mean, but i had a similar Case before and i was able to solve it (tbh with additional Help from here) with this complete measurement. Funny Part: it was Bad Schottky.

However you can continue to find the correct replacement for PD300 and May Check the suspected Mosfets again. Also Check all Diodes around the Controller.

And If this all will still Not work, then i See No other way than have a much deeper Look Into the Circuit.

[riki_22]

Re: La-c881p

Only adapter

PIN1 19,6V
PIN2 19,6V
PIN3 19,3V
PIN4 25V
PIN5 3,2V
PIN6 2,8V
PIN7 0V
PIN8 0v
PIN9 0v
PIN10 0v
PIN11 1,5v
PIN12 1,5V
PIN13 0,18V
PIN14 0V
PIN15 1,5V
PIN16 5,3V
PIN17 0V
PIN18 3,2V
PIN19 3,2V
PIN20 3,2V
PIN21 5,3V
PIN22 0V
PIN23 0,35V
PIN24 5,3V
PIN25 5,8V
PIN26 3,6V
PIN27 3,2V
PIN28 19,6V

Only Battery
PIN1 7,1V
PIN2 7,1V
PIN3 0V
PIN4 0V
PIN5 0V
PIN6 0V
PIN7 0V
PIN8 0,18v
PIN9 0,04v
PIN10 1v
PIN11 2,8v
PIN12 2,8v
PIN13 0v
PIN14 0v
PIN15 0v
PIN16 5,3v
PIN17 7,5v
PIN18 0,32v
PIN19 7,5v
PIN20 7,5v
PIN21 5,3v
PIN22 0v
PIN23 0v
PIN24 5,3v
PIN25 7,2v
PIN26 7,3v
PIN27 7,4v
PIN28 6,9v


what do you think about it?

[Sephir0th]

Re: La-c881p

1) I'm still Not convinced that PQ303 is fine and i still don't know anything about the condition of PQ305.

2) Clock and Data Voltages are a Bit lower when Adapter is present. But can't say this could be an issue. Also the 1.5V at BATPRES# seems a Bit too Low for me.

3) REGN measures usually more or less exactly 6V

4) Never saw ILIM Voltage above 1.X Volt, but couldn't mean anything.

[riki_22]

Re: La-c881p

1) I'm still Not convinced that PQ303 is fine and i still don't know anything about the condition of PQ305.

2) Clock and Data Voltages are a Bit lower when Adapter is present. But can't say this could be an issue. Also the 1.5V at BATPRES# seems a Bit too Low for me.

3) REGN measures usually more or less exactly 6V

4) Never saw ILIM Voltage above 1.X Volt, but couldn't mean anything.

PQ303 with adapter
D 19.6V
S 3.2V
G 3.6V

PQ303 with Battery
D 7.4V
S 7.5V
G 7.4V

PQ303 battery and adapter
D 19.6V
S 7.5V
G 8V

PQ305 Battery and adapter
D 7.4V
S 7.5V
G 0.005V

PQ305 with Battery
D 7.5V
S 7.5V
G 0.3V

PQ305 with adapter
D 2.5V
S 3.2V
G 3.2V

[riki_22]

Re: La-c881p

I know what you mean, but i had a similar Case before and i was able to solve it (tbh with additional Help from here) with this complete measurement. Funny Part: it was Bad Schottky.

However you can continue to find the correct replacement for PD300 and May Check the suspected Mosfets again. Also Check all Diodes around the Controller.

And If this all will still Not work, then i See No other way than have a much deeper Look Into the Circuit.

battery+adapter

PIN1 19,6V
PIN2 19,6V
PIN3 19,3V
PIN4 25V
PIN5 3,2V
PIN6 2,8V
PIN7 0V
PIN8 0v
PIN9 0v
PIN10 0v
PIN11 3,3v
PIN12 3,3V
PIN13 0,04V
PIN14 0V
PIN15 0V
PIN16 5,3V
PIN17 7,8V
PIN18 0V
PIN19 7,8V
PIN20 7,8V
PIN21 5,3V
PIN22 0V
PIN23 0,3V
PIN24 5,3V
PIN25 8,8V
PIN26 8,3V
PIN27 6,7V
PIN28 19,6V

I also made the measurements of pq303 and pq305 and also of pu300 what do you think now?

[Sephir0th]

Re: La-c881p

PQ305 is Open when Battery and Adapter is present, which isn't the correct behaviour Afaik.

Did you checked PQ305 in Ohms Mode between D-S-G before?

Actually my primary suspect is either PQ305 or PU300. to be Bad. But Check internal Résistance of PR320 before.

[piernov]

Re: La-c881p

PQ305 is Open when Battery and Adapter is present, which isn't the correct behaviour Afaik.

No that's expected.

[riki_22]

Re: La-c881p

PQ305 is Open when Battery and Adapter is present, which isn't the correct behaviour Afaik.

Did you checked PQ305 in Ohms Mode between D-S-G before?

Actually my primary suspect is either PQ305 or PU300. to be Bad. But Check internal Résistance of PR320 before.

PQ305 in Ohms is OL in D-S-G

PR320 where can i find it?

[riki_22]

Re: La-c881p

PQ305 in Ohms is OL in D-S-G

PR320 where can i find it?

what do you think if i try to replace
- PU300 BQ24777
- PD300 SDMK0340L
- PQ303 SIR472DP
- PQ304 SI7716ADN