ACOK at BQ24728 DA0R53MB6E0 issue

[mcplslg123]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

UVLO-Under Voltage Lock Out. At this point its not clear to me why acok is not present on this mb. Resistance at 65K is correct. Try removing PU12 from mb and then measure resistance on pin5 of pu8. If there is significant rise in resistance, PU12 may be bad but seems very unlikely to me.

[stingerchamp]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Check all nodes where acin attached.

Three points here

If reg6 voltage divider area resistors are ok it means
Acin signal is reflected back due to short in line

Acin attached to KBC

Acin attached to pu12

Quick solution: replace KBC Which is shorted internally, getting this signal but I do not recommend it

Second : first check pu12 Pg pin which is getting acin then try first solution

[emestee]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Yes it is measuring about 83K onboard, one side 6V and the other 0V

from datasheet: ACOK AC adapter detection open drain output.[...]

I'm confused. Which datasheet are you reading? There's no datasheet for BQ24728 that I could find. That chip doesn't have an ACOK output and the schematic calls it ACPRES and not ACOK. PR80 is supposed to be 100k and not 80k and, more importantly, it needs to be the same value as PR79. Is PR79 short? Is either of those resistors out of spec? Does PR80 get hot? What is the voltage across it when the board is powered up?

You say PR80 also pulls up ACDET, I dont understand how this is possible..

You should also probably disable PR175 to disable U12, and then lift pin 21 of the KBC to see if either part is shorted and pulling ACOK down. Note that the KBC pin is GPIO, which means (however unlikely) that wrong BIOS may cause this too.

[ruletero]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

I had a similar case months ago, the kbc acin pin was short, you need to remove the KBC and see if the ACIN goes up. Before I measured resistance on the pin and it did not indicate short but it was. Yes.. already I read you has changed the KBC but it was my case.

[emestee]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

I had a similar case months ago, the kbc acin pin was short, you need to remove the KBC and see if the ACIN goes up. Before I measured resistance on the pin and it did not indicate short but it was. Yes.. already I read you has changed the KBC but it was my case.

This is actually typical because internally, there are several mosfets and a latch to control the function of the GPIO and the pull up. The shorted mosfet may not be connected to the pin until the KBC is fully initialized. I know this because I've been reverse engineering KBC firmware and basically the datasheets speak to me in tongues while I am dreaming.

An interesting solution to this problem would be to hack the firmware to remap the pin and then move the ACIN to another pin, provided an ADC isn't required. However I imagine for most people just replacing the KBC would be a far better idea.

[mcplslg123]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

As per post#1, he has already replaced kbc.

[emestee]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Actually he also replaced the converter with another BQ, and I am not 100% sure they are interchangeable. Maybe the divider on ACPRES needs adjustment?

[stingerchamp]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

That is strange

[SMDFlea]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Check all nodes where acin attached.

Three points here

If reg6 voltage divider area resistors are ok it means
Acin signal is reflected back due to short in line

Acin attached to KBC

Acin attached to pu12

Quick solution: replace KBC Which is shorted internally, getting this signal but I do not recommend it

Second : first check pu12 Pg pin which is getting acin then try first solution

You might be on the right track ,and @emestee too .EDIT: and @mcplslg123 post #21

https://ascnb1.ru/forma1/viewtopic.php?f=231&t=115324

[stingerchamp]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Thanks @SMDflea

Btw in schematic diagram power good signal direction is wrong, it is an output signal not input

Pu12 Pg is the culprit pin

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

UVLO-Under Voltage Lock Out. At this point its not clear to me why acok is not present on this mb. Resistance at 65K is correct. Try removing PU12 from mb and then measure resistance on pin5 of pu8. If there is significant rise in resistance, PU12 may be bad but seems very unlikely to me.

PU12 removed but no change to resistance

UVLO is not clear to me, where can I measure it?

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

I'm confused. Which datasheet are you reading? There's no datasheet for BQ24728 that I could find. That chip doesn't have an ACOK output and the schematic calls it ACPRES and not ACOK. PR80 is supposed to be 100k and not 80k and, more importantly, it needs to be the same value as PR79. Is PR79 short? Is either of those resistors out of spec? Does PR80 get hot? What is the voltage across it when the board is powered up?

You say PR80 also pulls up ACDET, I dont understand how this is possible..

You should also probably disable PR175 to disable U12, and then lift pin 21 of the KBC to see if either part is shorted and pulling ACOK down. Note that the KBC pin is GPIO, which means (however unlikely) that wrong BIOS may cause this too.

Currently I have soldered a BQ24735 [from the forum is mentioned as alternative] and that has a datasheet. Both PR79 and PR80 were removed and measured 100K. PR80 6V from side to side.

PR80 doesn't nothing to do with ACDET

PR175 doesn't exist, it's just a line at pcb

After lifting pin 21 of the KBC, ACIN still remains low BUT the system powers on as the floating pin has 2,6V

So, there's somewhere an issue but if that cannot be found, working it like that could be ok?

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

ok, some issue with PU12
according to https://ascnb1.ru/forma1/viewtopic.php?f=231&t=115324
pin 16 should have 19V
I have 0 there, no issue with cap pc131

[emestee]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Both PR79 and PR80 were removed and measured 100K. PR80 6V from side to side.

You previously said that it has 0v on the exit. What changed? Or was this a bad measurement?

PR175 doesn't exist, it's just a line at pcb

I only mentioned is as a method to disconnect PU12

After lifting pin 21 of the KBC, ACIN still remains low BUT the system powers on as the floating pin has 2,6V

Do you mean ACOK remains low?

Which floating pin? Do you mean the pad under the lifted pin or ACDET? ACDET should be 2.6v (and was in your first tests). IIRC it should not be anywhere near the KBC.

If you're saying that you lifted KBC pin 21 and ACOK still doesn't go up, then the good news is the KBC isn't what's causing this. The other alternative is PU12. Disconnect it and see if ACOK goes up. Remember this is open drain, 0v doesn't mean the chip isn't giving out voltage; it means the pull up voltage isnt there to begin with, or the chip (or something else) drops it to the ground.

pin 16 should have 19V

Replace PU12 then.

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

You previously said that it has 0v on the exit. What changed? Or was this a bad measurement?



Replace PU12 then.

The 6V I mention is voltage difference from one side to the other so still 0 V on exit.

replacing PU12 should be the fix, I will as soon as I'll find a replacement and post the results

[mcplslg123]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

I had a doubt on PU12 as mentioned earlier at post#21. Lets wait and see the result.

[rookieme]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

after replacing PU12 all worked as should
I had GS7502Q3, I placed GMT-G5934 I found at a scrap M/B.
I have to mention that:

GS7502Q3 = GMT-G5934 = P2806

Hope that will help sb with any similar repair


Thank you everyone for the granted knowledge from this repair.

[emestee]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

after replacing PU12 all worked as should
I had GS7502Q3, I placed GMT-G5934 I found at a scrap M/B.
I have to mention that:

GS7502Q3 = GMT-G5934 = P2806

Hope that will help sb with any similar repair


Thank you everyone for the granted knowledge from this repair.

We should have a little party every time someone finishes with a successful repair. Congrats.

[stingerchamp]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

Great news, congratulations
We only guided you it was you who repaired it

Congrats again,

[mcplslg123]

Re: ACOK at BQ24728 DA0R53MB6E0 issue

We should have a little party every time someone finishes with a successful repair. Congrats.

The cost of the party will be more then the cost of repair.LOL