Everything looks connected to gnd

[hansie55]

On the mobo from HP8560p it have a short to gnd, but it looks to be all over the board in different areas. Is there a general supply where this can be generated.? the mobo is totally dead, I have 18,4V on Vin of the RT8205C.
The rest is all zero. I changed it for a TPS51125, but no result/
Both with the Ohm meter and Diode meter I get 0 in the 3V and 5V connections.
No short in the big capacitors or coils.
So Vbatt and Vadp are present but the V3A and V5A are shorted to gnd.
And most likely the rest too. No schematics, so I try to find things via datasheets of components.
Anybody pls advise.
Thx in advance

[highpulse]

Re: Everything looks connected to gnd

hey hansie , first of all chek if you receive 19 volts on B+ side of the mosfet on te 3.3 and 5 volts rails . if you notice a lot of shorting it could be due to short on 19 volts line , chek what voltage you got on the b+ of cpu v core and man 3.3 and 5 . and let me know here .
if you notice you got nothing , follow the dc in circuit were are OCP OVP circuit are , and also the main mosfet on the dc in . you will notice a mosfet were 19 volts will not pass , so you will inject 19 volts on that side were you didn't find voltage , and see if it get in short or not .. well do does first steps and let us know .

alltough let us know boardcode to follow schematcs

[hansie55]

Re: Everything looks connected to gnd

Thx Highpulse,
Boardcode: Cure_Dis-HR_HPB
there is nothing out there, I have to try without and locating parts is difficult.

[highpulse]

Re: Everything looks connected to gnd

no schematic yet my friend , so like i meentioned , chek on tge big capacitor (ceramic ones) near CPU socket , were you will find the main cpu coils as also the main cpu fets , usually you should get 19 volts on some of the fets/caps if you do not have anything it seems short somewere on 19 volts rails , very easy to find and fix if you got a powerlab .

[hansie55]

Re: Everything looks connected to gnd

Near CPU socket everything is 0V.
On picture I put the measured voltages around the power connector.
The power ID (pin3) is only 0.95 V at the connector, while the input is 18,4V
I don't have a labpowersupply, is there any way I can simulate that?

[megaraider]

Re: Everything looks connected to gnd

I don't have a labpowersupply, is there any way I can simulate that?

Use a common ATX power supply (e.g. from a desktop computer).
To make it power up connect PS_ON to ground (hint: on the 20 pin molex main power connector PS_ON is the green wire, ground any black wire).
Then start by using the lowest voltage available 3.3V (orange wires).
Only use the 5V if the previous didn't work out (red wires).

[hansie55]

Re: Everything looks connected to gnd

Thx a lot, I understand. What I don't know yet is where to connect the wire on the mobo

[hansie55]

Re: Everything looks connected to gnd

For the pictures above

[highpulse]

Re: Everything looks connected to gnd

ok so 0.95 means you got problem on 19 volts line , if all is at gnd so seems short on a capacitor , as megaraider says its a option , using a ATX supply meanwhile she will only give 12 volts max , so i dont know if it will be enough , due to open close first fet gate /charger ic .. but try to follow frmo dcc jack and go trough the mosfet , there will be one with 19 on both sides drain a source , but there will be one that only have 19 volts on the side , so you inject the 19 volts on the side were you got 0.96 , this will make the board to heat up a bad part , find it and remove it

[hansie55]

Re: Everything looks connected to gnd

I'm sorry, but I can't find the mosfet where the 0.95V pin 3 (ID) is going to. I tried with the meter all over the board. I can follow the line about 10 cm till a component that is not assembled and then it disapears in the board and the onliest place I can find it on the other side is on the docking connector, I know that HP needs the ID pin, else it will not work,
so I was looking for the track on the mobo already but could not find it.

The voltages are in the picture

[highpulse]

Re: Everything looks connected to gnd

ok so nevermind , simple chek on cpuvcore
mosfet side that receive B+
inject there 19 volts
and start chekng for hot spots
easy to find if you spray with IPA

[hansie55]

Re: Everything looks connected to gnd

I think it's best you tell me where on the picture, I don't have schematic and read from other schematics I find dangerous.

[fddizon]

Re: Everything looks connected to gnd

take a nice picture near dc jack with parts that have 8 legs on them.

like these two pictures

https://www.badcaps.net/forum/attach...5&d=1372652742

https://www.badcaps.net/forum/attach...4&d=1372652742

[highpulse]

Re: Everything looks connected to gnd

near the mosfet on cpu vcore , jp 3001 , what is the voltage there? if you got here 0.97 ok , then solder a wire on the JP3001 , and inject here 19 volts
and start looking for hot spots (it will be some capacitor getting ultra hot or even a mosfet sending B+ to gnd or leak between drain and gate

[hansie55]

Re: Everything looks connected to gnd

take a nice picture near dc jack with parts that have 8 legs on them.

like these two pictures

https://www.badcaps.net/forum/attach...5&d=1372652742

https://www.badcaps.net/forum/attach...4&d=1372652742

herewith

[hansie55]

Re: Everything looks connected to gnd

near the mosfet on cpu vcore , jp 3001 , what is the voltage there? If you got here 0.97 ok , then solder a wire on the jp3001 , and inject here 19 volts
and start looking for hot spots (it will be some capacitor getting ultra hot or even a mosfet sending b+ to gnd or leak between drain and gate

0,64v, which I also have on some mosfets over the board

[highpulse]

Re: Everything looks connected to gnd

well ok , but inject on the side were you got 0.64 volts on the CPU CORE MOSFETS forget the outher , and chek what part will get hot

[hansie55]

Re: Everything looks connected to gnd

I don't geet it, should I forget about JP3001 ?
On the 6 mosfets near the cpu I got 0V

It was a mistake, I only got 0,64V on the mosfet near the power connector Q2806., sorry

[fddizon]

Re: Everything looks connected to gnd

try this... see attached

when you find the fets that has one side with 19v and no voltage in the other side, thats where you will inject the 19v instead from dc jack

[hansie55]

Re: Everything looks connected to gnd

try this... see attached

when you find the fets that has one side with 19v and no voltage in the other side, thats where you will inject the 19v instead from dc jack

U did that and attached the 19V to pin 1 of Q2806.
Now U2901 (RT8205C) got real hot, I took it out, but still a short there.
L2901, C2901, C2902, L3241 and L3242 got warm, but U3241 ( EC1PG) is getting red hot. (I still have to find the real partnumber.)
Multiple shortage??