How to check short in power rail

[ktmmotocross]

Hello i need to know how to check short in power rails. I have some short in power rails and i check resistance but on processor, VGA or chipset i get resistence under 1ohm.
anybody know how to chceck that short?

[loser18]

Re: How to check short in power rail

Take out the CPU...check again...should have some resistance now...GPU & GMCH have sometimes low resistance eg. 10-15ohms...

[ktmmotocross]

Re: How to check short in power rail

yes i know that i take out processor i have some resistance but in GPU or chipset i get resistance less then ohm about 0.2ohm.

[loser18]

Re: How to check short in power rail

What's the mobo model number...

[ktmmotocross]

Re: How to check short in power rail

its HP dv6700 with nvidia GPU, it shuts right after power switch. its so fast that i cannot check power on power rails and resistance dont show enything

[loser18]

Re: How to check short in power rail

Here's schematic if it's AT3...
Which coils are shorted?

[ktmmotocross]

Re: How to check short in power rail

not mine board. i have Nvidia MCP chipset and Turion processor.
PL3 - 0.2ohm
PL11 - 0.2ohm
PQ25 - output - 0.3ohm
here is diagram
https://cdn.badcaps-static.com/pdfs/...f1d82042d0.pdf

[loser18]

Re: How to check short in power rail

If you don't have lab PSU it's a pain in the arse to look for shorted components...
Desolder PL3 & PL11 and check which pin/side is shorted...

[ktmmotocross]

Re: How to check short in power rail

How can PSU help me to detect vhere i have short?

[loser18]

Re: How to check short in power rail

You will inject voltage to shorted rail & look for components which are heating up...
Need a proper lab PSU with voltage & current regulator...

[khaahk]

Re: How to check short in power rail

What do you mean by PL3 - 0.2 ohm ?
Are you measuring resistance across PL3 or measuring from PL3 relative to GND?

not mine board. i have Nvidia MCP chipset and Turion processor.
PL3 - 0.2ohm
PL11 - 0.2ohm
PQ25 - output - 0.3ohm
here is diagram
https://cdn.badcaps-static.com/pdfs/...f1d82042d0.pdf

[ktmmotocross]

Re: How to check short in power rail

To ground of course.

[khaahk]

Re: How to check short in power rail

Sorry, just checking...
Then lab PSU is the easiest way.
Way too many shorts for one mainboard (or do they all end in nvidia mcp67)?

[loser18]

Re: How to check short in power rail

Had shorted 19V rail...
Found 2 shorted FETs today (without PSU)...
Didn't take more than 15min...
Also had to use boardview file as no markings on board itself...
Was like schematic-boardview-mobo-desolder lol

Possible, if you following schematics...(but still pain in the arse)

[ktmmotocross]

Re: How to check short in power rail

i think its that mcp, because it have 1,2 and 3v and all this power rails is shorted. removed pl3 and pl11 and short is on chips side. gpu uses only 1.2v so i think MCP is shorted.

[loser18]

Re: How to check short in power rail

Need to reball...or try reflow if You don't have bga machine...
Also did you check PC43, 44, 45, 113, 19, 111, 13, 109 and PU1?

They're most likely ok, but you never know...

[ktmmotocross]

Re: How to check short in power rail

damn have a bad luck. Unsolder MCP > nochange still short 1.2v and 3v

so i desoldered GPU and all shorts is gone.
I dont have a knowledge that GPU uses 3V rail

[ktmmotocross]

Re: How to check short in power rail

I forget the vga rams, it uses 3v