Missing ACDRV in Quanta 0P5D

[orientalsniper]

Hello all, been trying to diagnose this board all night and haven't been successful, so once again I come here for help.


Board has a history of being liquid spilled, but I see no corrosion since they brought it to me the day after.


The DC-IN mosfets don't seem to be shorted (PQ1001 & PQ1002).


I've replaced the PU1001 (BQ24728) with a BQ24725 with no changes.


I've also removed PR1020 the 4K resistor connecting the charging IC with the two dc-in mosfets to see if 25V would be present for ACDRV, but I still get 0V.


Voltages for PU1001 are:
REGN: 6V
VCC: 19V
ACDET: was 2.0V, but I changed PR1024 for a 330K resistor to get 2.6V
ACIN/ACPRES: was 0V but after getting 2.6V in ACDET, it's now 3V
ACDRV: 0V <------ this is I what I need

[Bonzas]

Re: Missing ACDRV in Quanta 0P5D

Hello all, been trying to diagnose this board all night and haven't been successful, so once again I come here for help.


Board has a history of being liquid spilled, but I see no corrosion since they brought it to me the day after.


The DC-IN mosfets don't seem to be shorted (PQ1001 & PQ1002).


I've replaced the PU1001 (BQ24728) with a BQ24725 with no changes.


I've also removed PR1020 the 4K resistor connecting the charging IC with the two dc-in mosfets to see if 25V would be present for ACDRV, but I still get 0V.


Voltages for PU1001 are:
REGN: 6V
VCC: 19V
ACDET: was 2.0V, but I changed PR1024 for a 330K resistor to get 2.6V
ACIN/ACPRES: was 0V but after getting 2.6V in ACDET, it's now 3V
ACDRV: 0V <------ this is I what I need

Remove PQ1002 and check if you get acdrv on pq1001

[reformatt]

Re: Missing ACDRV in Quanta 0P5D

Make sure you don't have your main power rail shorted, that's the usual thing I see when ACFET/RBFET aren't opened as the BQ IC has S/C protection. Check it at PR1001.

[reformatt]

Re: Missing ACDRV in Quanta 0P5D

Also noted that the values for PR1023/PR1024 don't seem correct on the schematic. Other Quanta boards have this as 430k/70k for the same BQ IC (which should give you roughly 2.6V for a 19V supply). But this is 430k/51k which gives you 2V. Other components in this area (PQ9/PQ11) seem to be nostuff so can be ignored. BQ24725 IC needs between 2.4V and 3.15V for ACDET, no datasheet available for BQ23728 but you'd assume it's the same. Odd!

[orientalsniper]

Re: Missing ACDRV in Quanta 0P5D

Remove PQ1002 and check if you get acdrv on pq1001

I forgot to say I've removed the 2nd dc-in mosfet PQ1002 and I still didn't have ACDRV, but I don't know if this is relevant, I measured 0.8V on the drain (pin 5) of PQ1002 without the mosfet soldered on.

Make sure you don't have your main power rail shorted, that's the usual thing I see when ACFET/RBFET aren't opened as the BQ IC has S/C protection. Check it at PR1001.

I don't think there's a short, I'm getting a 0.450V in diode and 2 mohms resistance (steadily going down) on PR1001.

Also noted that the values for PR1023/PR1024 don't seem correct on the schematic. Other Quanta boards have this as 430k/70k for the same BQ IC (which should give you roughly 2.6V for a 19V supply). But this is 430k/51k which gives you 2V. Other components in this area (PQ9/PQ11) seem to be nostuff so can be ignored. BQ24725 IC needs between 2.4V and 3.15V for ACDET, no datasheet available for BQ23728 but you'd assume it's the same. Odd!

I can confirm the resistors are 430K and 51K on the board, the components in ACDET3 are not present like you said.


I did mention I had to replace the 430K resistor with a 330K resistor to get 2.6V, but I don't think it helped me get ACDRV.

[orientalsniper]

Re: Missing ACDRV in Quanta 0P5D

Also, what's the difference between ACOK and ACIN/ACPRES, the BQ24725 datasheet has pin 5 as ACOK, but this board schematic uses the terms ACIN/ACPRES.

[reformatt]

Re: Missing ACDRV in Quanta 0P5D

Just a naming convention from whoever drew the schematic I think. It's function is the same.

BQ24728 is a custom IC for the OEM's I believe, hence the datasheet hasn't been made publicly available as a result. But I think the general parameters are the same, as all BQ IC's tend to use the same general logic. I still cannot explain the values for ACDET on this board. Every other design I've seen using this IC results in 2.6V for a 19V adaptor so this makes no sense to me.

There are a few conditions that will result in ACFET/RBFET being switched off and are usually as a result of overcurrent either to the main supply rail or in the battery charger MOSFET's. I'm thinking you may have an active short somewhere so a thermal camera might be the way to go here.

[orientalsniper]

Solved

SOLVED

I was able to fix it, but it was by pure luck and 0% skill, so I went back to the area that had sign of liquid and noticed a solder jumper with a brownish color, when I took off the solder, I could see the trace was broken, I soldered it with a wire and it worked, I got ACDRV and laptop also turns on with no problem.

I checked the boardview and that trace was not in there, I was able to trace it back to +VAD, I'm glad I was able to repair this, but I would be more happy if I was able to diagnose that +VAD was the cause.

Can someone explain to me how +VAD is necessary for ACDRV generation? I don't think it even feeds the charger IC, I'd be glad to be educated about it.

I also undid everything (put back charger IC, ACDET resistor), all it needed was the trace to be repaired.

What I learned:

ACDET can be okay with 1.9V
ACOK/ACIN/ACPRES (however you're gonna call it) is okay with 3V
BQ24728 is compatible with BQ24725 and BQ24738

[reformatt]

Re: Missing ACDRV in Quanta 0P5D

So you are saying you had no continuity between the source of PQ1001 and the source of PQ1002? Usually ACDRV will appear momentarily and the IC will give up after 7 tries if an abnormality is detected. You may have seen a pulsing when the board first has power applied to it. Since no voltage appeared at the drain of PQ1002, this is probably considered a short by the IC so it removes ACDRV.

PQ1006 is there for reverse polarity protection, and normally it's biased off. So I don't think it played a part.

[orientalsniper]

Re: Missing ACDRV in Quanta 0P5D

So you are saying you had no continuity between the source of PQ1001 and the source of PQ1002? Usually ACDRV will appear momentarily and the IC will give up after 7 tries if an abnormality is detected. You may have seen a pulsing when the board first has power applied to it. Since no voltage appeared at the drain of PQ1002, this is probably considered a short by the IC so it removes ACDRV.

PQ1006 is there for reverse polarity protection, and normally it's biased off. So I don't think it played a part.

I never checked for continuity between the source of PQ1001 and PQ1002, I've already put that laptop back.


Can you tell me the difference between +VA_AC, +VA and +VAD? Is the power adapter the source for all three? Thanks again.

[reformatt]

Re: Missing ACDRV in Quanta 0P5D

Just different test points on the board really and a hangover from when the board was being developed. PL1001/1002 may have been fitted with RF chokes to pass some the RFI requirements in some countries, but in production were removed with shorts. From a troubleshooting perspective, +VA and +VAD are test points before and after the first FET.

[orientalsniper]

Re: Missing ACDRV in Quanta 0P5D

Just different test points on the board really and a hangover from when the board was being developed. PL1001/1002 may have been fitted with RF chokes to pass some the RFI requirements in some countries, but in production were removed with shorts. From a troubleshooting perspective, +VA and +VAD are test points before and after the first FET.

I see.


Thank you for your assistance, I would had been stuck on this repair without your help.

[piernov]

Re: Solved

I don't think it even feeds the charger IC

Goes to charger IC CMSRC pin through PR1021.