laptop hp dv6-3132 dead, no lights at all

[starling22]

When the power supply is plugged in there is power on the motherboard but no lights at all. I have removed the battery, which seems dead as well.

I measure power on the section up to the first MOSfet switch which is turned off.

There is power to at least one pin on the OZ8681 charge controller chip. This is where I am stuck as I can not find a data sheet for this chip and see how it works.

Can anyone help pointing to spec sheet download. I have searched on the net for a couple of hours but admit defeat.

Anyone that can explain roughly how that chip works? Mainly need to know if the DC supllied to the chip sends DC power out in the form of the VDDA and VDDP port signals?

Still Trying to figure out how to attach circuit, my present laptop scrambles font when trying to browse for file.

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

Still struggling to find my way around here but progressing. I have managed to attach the pdf file of the charger circuit wher I believe I am stuck at the moment.

There is approx +19V on +VA, +VAD and +VAD_1, theis means there should be DCIN on the OZ8681, though I need to get a bit closer to the actual pin and measure.

So I am asking if there is DCIN should the chip send out the VDDA and VDDP (pins 6 and 15)

[piernov]

Re: laptop hp dv6-3132 dead, no lights at all

VDDA and VDDP are useless as far as I understand it.
Your issue is that PQ42 has no voltage on its source even though there is voltage on the drain? What is the voltage on its gate? What is the voltage on the gate of PQ4?

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

piernov
Thanks for replying. PQ42 gate voltage is zero, ie it is preventing the main voltage to be established.

I have not yet positively identified measurements around PQ4 I got sidetracked checking the smartpin path to page 32 and a bit mystified. I have however returned to look at the OZ8681 and the PQ4 circuitry.

PQ4 has approx +9V, the two 100K resistors accross the gate seems to set the voltage.
PQ3 has 320mV on base
PD3 has ~2V on cathode

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

OZ8681 pin1, VAC and DCIN is +19V there was a test point near the chip showing this value. Took the risk and measured directly on the pin, the first one from the edge so I could gently move up to the pin from one side with my needle probe. It is high voltage, ~19V.

pin9, ACAV, 8681_ACAV measure +3.25V the other side of PR84 seems to be varying, not steady. Leaving this at the moment.

pin6, VDDA, 8681_VDDA measure +5.8V
pin15, VDDP, 8681_VDDP giving me trouble not sure I have the correct test location, directly on the chip is a bit intimidating.

Will take a break and come back to this. I notice that the area of the pcb where power comes on to the board seem to creep up in temperature over 37 deg C, hot to the touch. Unable to measure current consumption until I rig up a break out connector.

[piernov]

Re: laptop hp dv6-3132 dead, no lights at all

What's the voltage on D/C#, P2805PG and +VH28?
I think the issue is on the ACIN line. It shouldn't be varying as far as I understand it, you should get 3.3V on both sides of PR84, allowing PQ3 to short ACOK# to ground.

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

I had to pack away the laptop, my wife wanted to vacuum clean the room. Will soon be set up again. Working out of the computer room at the moment and was trying to find the data sheet for P2805MF (=G5933) with little luck so far but also found a badcaps thread where an equivalent listed. Shown in brackets. When I saw the schematics I recognised the switched capacitor up converter, 1.5xVin (here 19 V) = ~28V.

There is probably some reason why the outpu is designated VH28. This is the voltage I should expect. The interesting thing when searching I stumbled over this post:

https://www.badcaps.net/forum/showthread.php?t=20831

A problem laptop which showed +VH28=28V apparently here this was wrong. I may have misunderstood something. Anyway just a curiosity, it was in this post I recognised what the P2805MF was doing.

if D/C# is 0V the transistor is off but what pulls the collector voltage up to ??V, which could turn on PQ42.

I will set up for testing again.

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

I have spent more than an hour trying to find the PU2 P2805MF the IC generating the VH28/28V signal. I believe I have identified all 8 pin ICs but not yet found the PU2 designator on the motherboard.

When you look at the schematic is there anywhere indication where a particular component is place. Anything that indicates what side on the PCB one can find the components.

I hope that it is the use of a different IC that is causing my trouble but so far I have not even found components R and C associated with the P2805MF.

Stumped at the moment.

[piernov]

Re: laptop hp dv6-3132 dead, no lights at all

+VH28 is produced by PU8 on the VOUT pin, the measurement was only to check if PU8 is good. It if outputs 28V it should be good. It is the voltage which will be used on the gate of PQ42 (look at PR15), but for this to happen it must not be pulled to ground by PQ4.

0V on D/C# is ok, it means that PQ18 doesn't short ACOK_IN to ground. (so the base of PQ3 is not shorted to ground)
However I still see no explanation why ACIN wouldn't be 3.3V, I must be missing something. Perhaps an issue with the KB3926QF which is also connected to this line?

PU2 is probably not present on this board. It is annotated as no stuff by the '*' in front of the part number (or value) on the schematics. However this schematics is a bit confusing because the parts inside dark blue squares are actually present on the board, even though they have the '*'.

Also there is no way to know the location of the component with only the schematics, you'll need a boardview for that (which is not available for this board AFAIK). Though most of the times the motherboard layout is made in a logical manner with different blocks having different responsibilities, so you won't search for a charger issue in the GPU area for example. The components around an IC can help you identify it too (number of resistors, capacitors and inductors and the pins they're connected to).

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

Great tip for me about the '*' meaning things may be missing. I think you are right PU2 is nonexistent. You mentioned PU8 was generating HV28, based on counting the pins this is a 20 pin IC so using this as starting point I located the P2806, attached picture.

It is midnight here so I am struggling with lighting tonight making identification difficult. I have annotated what I think is pin 17, VOUT and the other arrow shows top of a capacitor where I measured +29V. On the right diode footprint, empty by the way, I measured 19V most likely +VA on p.41 near PU8.

I will see if I can get the oscilloscope on the ACIN tomorrow to see what is going on, is there really a an AC component on the one sid ot the components.

[piernov]

Re: laptop hp dv6-3132 dead, no lights at all

Btw did you check for a short to ground on +VIN?

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

piernov
Well, I almost fell in the trap os saying yes I had but when I looked in my notes I could not find any record so I repeated a conductivity check near +VIN.

There is a diode of some sort, I don't think it is an ordinary diode. Designated PD23 a P4SMAJ20A. I found data sheet and attached copy looks like being a transorb or ? whatever. Initially I seemed to get diode behaviour but I went back and repositioned the board so I could get a bit more force on my needle probes. "Shorted diode".

Measuring between cathode and GND less than 10 mV, so also short, so the short is probably not the diode but some other component but could of course be the diode.

Assuming there is a short this suddenly looks like a lot more work???

Assuming there is a short this suddenly looks like a lot more work???

[piernov]

Re: laptop hp dv6-3132 dead, no lights at all

Ah yep if you've got a short on +VIN that could explain why PQ42 doesn't open… (at least I hope it's the cause)
PD23 is a TVS diode, it's designed to somewhat protect the circuit against voltage spikes. Those diodes let through all the current past a certain voltage (like a zener diode), and they can die in this case. Try to remove it and see if the short is still present.

If it's not the TVS diode, it can be pretty much anything else on the +VIN line. Most of the other power rails of the motherboard are created from +VIN using buck converters. You'll have to inject voltage on the +VIN line and find which component gets hot. Make sure to do that without any component connected to the board, start with 1V and check first if the PCH gets hot, you surely don't want to burn that. If it doesn't and nothing else gets hot, you can increase the voltage a little.

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

I have been counting capacitors on the +VIN rail, it amounts up. Well with a short on the board and heating up near the power entry it narrows the area a bit.
Basically the area on the picture attached here gets up to about 40 deg C, hot to the touch but no specific component.

Will get my little infrared temperature indicator out an try and see if this can pick a hot spot, small sensing area on the unit. The generated heat may of course not be due to the short either.

I have a variable power supply 3-27V 1 Amp with current limit as low as 20-50 mA and as well I can put a string of 1A rectifier diodes in series to get down to approximately 1V when current start flowing.

[piernov]

Re: laptop hp dv6-3132 dead, no lights at all

If the PCH and the GPU don't get hot, you can try increasing the voltage, maybe a couple of volts or more. It would be nice to monitor the current consumption.

PS: there is no picture attached.

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

Sorry about the picture missing, I think I got sidetracked looking for a really good picture of my motherboard so I can annotate the bigger components. A few days away from this work and I have forgotten where I got to, I put it down to old age.

Yes good point about keeping an eye on the current consumption. I have just had power on the board and measured 96-100 deg F, somehow I managed to change mode from deg C and forgotten how to change it back.

The board area that hots up now attached.

Adding external powering of the motherboard +VIN, I think I might try and run it off a 12V drill battery and using a simple LM317 voltage regulator. This would ensure complete isolation from the mains, just in case. For short period of time I can get 3A I think that should be plenty.

When I come to think about it, if I have a short then the smart pin is not doing any good so if I supply 19V from my variable 1A I will get an idea of how much current goes in right now in the faulty state.

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

I have spent time making a component identification map to help me manage what I have identified. Getting back to troubleshoot.

When I apply power I find that PQ42, which is OFF, preventing +VIN. While it is off some current must be passing because it does get hot to the touch after a 1 to 2 minutes. The longer power is on the a greater area around the device also gets warm to the touch.

I have got my power supply set to 3.2V, lowest I can go and set a current limit of 400mA. Applying power to the Cathode of PD23, a voltage of approximate 0.120V so the short seems to have some resistance.

With this setup I can only go to about 0.9A. When I use the 0.9A setting I measure aproximately 0.350V. The ground reference changed to the two board support pads nearby (to the left of PD23, there is a sticker over the second ground hole area, see attachment) where I use alligator clamping.

[piernov]

Re: laptop hp dv6-3132 dead, no lights at all

0.9A and 0.350V would mean a 0.3W power consumption. It's not gonna get really hot if at all, I usually try to have a 2-3W power consumption for the component to get really hot. You would need a higher current limit. Either you need to find a better power supply or you could try to disconnect every caps and MOSFETs on the +VIN line, but well…
What's the exact resistance between +VIN and ground? (I guess somewhere between 0.3-0.4 ohm)

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

I agree I will have to get my heavy dude, 30V-20A variable supply off the shelf and use a 1 ohm 50W power supply or similar.

[starling22]

Re: laptop hp dv6-3132 dead, no lights at all

I made up a resistor of 3 resistors, 1 ohm wirewound 7W, in parallel. They were placed in the airstream from the sizeable fan exhausting at the rear of my power supply. I found out that I needed a lot of power to make anything warm.

The mobo still had the processor and fan installed up till now. When I applied power accross the PD23 (careful with polarity) I had trouble sensing anything getting hot. Kept increasing the power.

When applying 20W power I noticed the heatsink over the processor, with an outrigger plate to pick up heat from two coils and 8 mosfets, that area got quite hot.

Removed the processor, fan and associated singe heat sinn module. Started applying power again and when I apply aproximately 12W then I can feel the 8 mosfets getting hot.

Power: 5A @ 1.68V ( app 8 watts) =>> 0.336 Ohms. My DVM uses 48 micramps, assuming the short is 0.336 ohms, the DVM would need to measure around 16 microvolt. Well my instrument would not be able to measure that low.

I need to check the 8 MOSfets, initial check on one seems to be shorted but am having trouble figuring layout. I hope I am in the right area.

Doing an ohms check in both direction shows roughly 10 mV in both directions for all 8 MOSFET devices.

The device names almost invisible but I believe there are two types in pairs and from Fairchild

DA37DV
DA37XX

Been unable to find any datasheet on either of those two so far.

Can anybody help with data sheet? Equivalent replacements aslo appreaciated.