HP Compaq C700 says charging but isn't

[sparker1]

I am trying to fix the charging circuit on this laptop. Windows says it is charging but the charging icon stays at 0%. There is plenty on google about this and one user replaced PQ1 and fixed it. I am looking at doing the same but I can't tell if PQ1 or PQ2 is bad. They are N channel mosfets Fairchild FDS6675BZ. They look very hard to remove without damaging the plastic fittings nearby. Here are the readings I got with my DMM set to continuity/diode mode (I've highlighted the difference from PQ2 and PQ1 in red):

PQ1 Results:
All the source pins to the drains are open circuit.
Source to gate is open circuit
All the drains to source pins give around 0.513.
Gate to source pins show 1.827.
There is continuity between all source pins and the same with all drain pins.
Drains to gate show open circuit
Gate pin to drains is open circuit

PQ2 Results:
All the source pins to the drains give around 1.665
Source to gate is open circuit
All the drains to source pins give around 0.511.
Gate to source pins show 1.827.
There is continuity between all source pins and the same with all drain pins.
Drains to gate show open circuit
Gate pin to drains is open circuit

I would appreciate it if someone with more knowledge would have a look at this information and let me know what they think. Does PQ1 look bad or not?

[sparker1]

Re: HP Compaq C700 says charging but isn't

The above measurements are in volts, according to the handbook on the continuity scale, I think. I have done more measurements using the resistance scale:

PQ1 Results:
Source to Drain – all open circuit
Gate to drains – all open circuit
Gate to source – all about 200 ohms
Drains to gate about 1280 ohms
Drain to Source:
Pins 5, 6 and 8 to 1, 2, 3 are 980 ohms
Pin 7 to pin 1 is 980 ohms but open circuit for pins 2 and 3


PQ2 Results:
Source to Drain – all open circuit
Gate to drains – all open circuit
Gate to source – all about 200 ohms
Drains to gate about 1280 ohms
Drain to Source:
All drain pins show about 980 ohms to all source pins

Does the red reading show PQ1 is bad?

All measurements were done in circuit.

[dj_ricoh]

Re: HP Compaq C700 says charging but isn't

hello my friend!
we must focus on PU1!

what`s the values on pin 5 and pin 7 with no battery power off/ then power on
and with battery power off /then on

[sparker1]

Re: HP Compaq C700 says charging but isn't

Thanks DJ Ricoh. I'll post the results. Is it OK to leave CPU in?

[sparker1]

Re: HP Compaq C700 says charging but isn't

hello my friend!
we must focus on PU1!

what`s the values on pin 5 and pin 7 with no battery power off/ then power on
and with battery power off /then on

PU1: DC/DC Converter for charging (MB39A126PFV-ER_SSOP24) -volts
Pin 5=ACOK and Pin 7=ACIN

No Battery:..........Pin5/Pin7
Power off...............0.00/0.00
Power on...............5.00/0.18

With Battery:........Pin5/Pin7
Power off...............0.00/0.40
Power on...............0.10/0.18

Measurements taken with RAM and CPU fitted. When power button pressed the laptop booted with all lights and fan spinning.

[sparker1]

Re: HP Compaq C700 says charging but isn't

There's an error above. The 5.0v should read 0.0v for no battery-pin 5-power on. Can't edit for some reason.

[dj_ricoh]

Re: HP Compaq C700 says charging but isn't

apparently ACIN in 0 and that should over 1.5v and ACOK needs to go in low state.
on the left side of the PU1 there is ACIN and PACIN , try to trace that PU2A and PU3 and see why you don`t have ACIN in PU1

[dj_ricoh]

Re: HP Compaq C700 says charging but isn't

until tonight I`ll make you a video how to remove that mosfet without destroying anything. ok?
a soldering tutorial

[sparker1]

Re: HP Compaq C700 says charging but isn't

Sounds great, thank you. I will try and trace those voltages.

[sparker1]

Re: HP Compaq C700 says charging but isn't

OK. PU3 : LMV431ACM5X = Power Management, Voltage References = Shunt:
Voltages:
pin1...............0.00
pin2...............0.00
pin3...............1.24
pin4...............1.24
pin5...............0.00
There was no change to these values when the power button was pressed.

PU3A : LM393DG: Voltage Comparator - voltages power connected/power on (start button pressed)
voltages:
Pin1................3.29/3.29
pin2................1.24/1.24
pin3................1.80/1.80
pin4................0.00/0.00
pin5................1.24/1.24
pin6................1.39/1.35
pin7................0.12/0.12
pin8................19.5/19.5
As you can see there was no change when the power button was pressed.

[dj_ricoh]

Re: HP Compaq C700 says charging but isn't

change that pu1!
do you have any spares?

[sparker1]

Re: HP Compaq C700 says charging but isn't

No. But I saw them on Ebay two for about $4.00 http://www.ebay.com.au/itm/360867133...84.m1438.l2649
Might take awhile. Will post back on results. Thanks DJ Ricoh for your kind help.

[dj_ricoh]

Re: HP Compaq C700 says charging but isn't

np sir!
when you tested pq1 and 2 did you took them out?
if not test them of the board to