HP CQ61 Short circuit Help

[NConstantinou]

i have Hp cq61 which has short +VIN to ground.
M/b is DA00P6MB6D0.
I removed PR61 and on +VIN side it is short to ground.
i checked PQ6 and shows that D is short to groud. i removed PQ6 and i still
get short to ground on pin 5,6,7,8.
i checked pin 2 with pin 8 and i get .485v.
i checked capacitors connected to drain with ESR meter and are shown ok.
checked PQ49 and D is short. checked pins 2 and 8 and i have .585v.
Gates are not short on any PQ.
checking all capacitors with ESR meter are shown ok

+VIN is the input of TPS5147A that goes on pin6.
removing TPS5147A i still get short on pin 6 which is the input (+VIN)

can someone HELP!

[piernov]

Re: HP CQ61 Short circuit Help

+VIN is the main power rail of the motherboard, there are many components on it so the best way to find a short to ground is to inject some voltage (start with low voltage, 1V), and check for anything that gets hot.
Schematics attached.

[NConstantinou]

Re: HP CQ61 Short circuit Help

i have done this, i connected dc power supply starting at 10v and full current BUT nothing
gets hot!

i have one question for you.

PU2 pins 9,10 when i removed this ic are solder together. i notice these 2 pins go on the outpt of PL8. is that ok!

[NConstantinou]

Re: HP CQ61 Short circuit Help

+VIN is the main power rail of the motherboard, there are many components on it so the best way to find a short to ground is to inject some voltage (start with low voltage, 1V), and check for anything that gets hot.
Schematics attached.

i have done this, i connected dc power supply starting at 10v and full current BUT nothing
gets hot!
i went up to 18v and still nothing is hot

[piernov]

Re: HP CQ61 Short circuit Help

PU2 pins 9,10 when i removed this ic are solder together. i notice these 2 pins go on the outpt of PL8. is that ok!

Yep it's fine, that's how it is designed.

What's the resistance between +VIN and ground? How much current does it draw when you inject voltage?

[NConstantinou]

Re: HP CQ61 Short circuit Help

The resistance is 9,1 OHMS.
as far as current i went all the way up to 5A gradually.

I notice PQ48 gets Hot but i replaced it with a new one

[piernov]

Re: HP CQ61 Short circuit Help

5A is the limitation you set, not the actual current draw by the board. With 9.1 ohms and 18V, it would mean the current drawn is 2A.
Did you inject voltage on +VIN? PQ48 shouldn't get hot if it's the case.
Also, with a 9.1 ohms short to ground, if you inject 18V something has to get hot. It dissipates 36W, that's burning hot. Otherwise you may have a short inside the board, and in that case the board may feel a bit warm.

[NConstantinou]

Re: HP CQ61 Short circuit Help

No, i haven't inject voltage on +VIN.

as far as i know i must connect dc power supply 18v on PR61 pin 2 which is the first point of +Vin!


Thanks Piernov