Locating short circuits with bnch psu

[scobie_21]

Hi Im looking for the quickest way to locate shorts on laptop motherboards. I have a bench supply but every time I connect it the over current trips out and I have to power it off then on again. Is there an easier way of locating suspect component/components?.


Many thanks

[smason]

Re: Locating short circuits with bnch psu

Hi Im looking for the quickest way to locate shorts on laptop motherboards. I have a bench supply but every time I connect it the over current trips out and I have to power it off then on again. Is there an easier way of locating suspect component/components?.


Many thanks

A better bench supply?
Sounds like a smartass reply, but with a good bench supply if you tell it to limit current to 1A, it'll sit there and feed 1A into a dead short or whatever, no need to reset it all the time.

I find it better to use a good low ohm meter and trace it that way.

That said, I failed to find a short on a Dell laptop motherboard last month. Tried the give it power and watch for smoke routine, no luck.

[scobie_21]

Re: Locating short circuits with bnch psu

No not a smart ass reply at all. much appreciated I will look into buying better psu. Can you recommend any ?.

[smason]

Re: Locating short circuits with bnch psu

No not a smart ass reply at all. much appreciated I will look into buying better psu. Can you recommend any ?.

There are a lot of similar supplies that look like this Chinese one:

Item 400396805866 on Ebay.ie (link was too friggin long and I'm too lazy to use a short link site)

[scobie_21]

Re: Locating short circuits with bnch psu

That's the exact same one I have.

[scobie_21]

Re: Locating short circuits with bnch psu

Actually its a slightly different model. Mine has not got the push button in the middle between the current and voltage knobs.

[scobie_21]

Re: Locating short circuits with bnch psu

So would I be right in saying I need one with a current limiting feature so it wont power off?.

[rievax_60]

Re: Locating short circuits with bnch psu

I use a 1 ohm resistor in series with my power supply. I try to stay under 0.5A. My power supply is a simple linear design and tends to get rather hot when run at low voltage and high current.

[Th3_uN1Qu3]

Re: Locating short circuits with bnch psu

Hi Im looking for the quickest way to locate shorts on laptop motherboards.

A milliohm meter.

[rievax_60]

Re: Locating short circuits with bnch psu

So would I be right in saying I need one with a current limiting feature so it wont power off?.

Are you starting from zero volts?

[scobie_21]

Re: Locating short circuits with bnch psu

No Im using 1v. I have a short on a dell motherboard that I cannot locate I have tried isolating different sections by removing some coils on at various regulators. The unit wont power on and the dell psu goes into protection mode after a second or so. I have a bench psu and as the short is on the 1.05v line to the PCh I have established the short is not on the regulator side by removing the coil on the output and the short stays on the output side ie. Pch supply voltage there are many components on that side and my bench meter cuts off after a second or so when I connect it to the circuit.

[scobie_21]

Re: Locating short circuits with bnch psu

A milliohm meter.

Can you explain a bit more on the method used please ?

[scobie_21]

Re: Locating short circuits with bnch psu

I use a 1 ohm resistor in series with my power supply. I try to stay under 0.5A. My power supply is a simple linear design and tends to get rather hot when run at low voltage and high current.

When you say you try to stay under .5A how do you control this ? I don't seem to have any current limit on my supply It just goes straight to protection mode and I have to switch of the bench psu then on again so theres no chance to find components heating up.

[smason]

Re: Locating short circuits with bnch psu

That's the exact same one I have.

Hmm does it not have a current adjustment?

This is the exact model I have:

[scobie_21]

Re: Locating short circuits with bnch psu

Hmm does it not have a current adjustment?

This is the exact model I have:

The one I have is a Zhaoxin PXN-1505d it looks almost identical to yours except theres no button in the middle for low/high Amp readings. I set the voltage to 1v and no matter what I set the current to as soon as I connact it to the circuit the bench supply just says 00 on both v and current readings and I had to power it off to reset it.

[smason]

Re: Locating short circuits with bnch psu

The one I have is a Zhaoxin PXN-1505d it looks almost identical to yours except theres no button in the middle for low/high Amp readings. I set the voltage to 1v and no matter what I set the current to as soon as I connact it to the circuit the bench supply just says 00 on both v and current readings and I had to power it off to reset it.

Weird. I can short mine out and it'll limit current but I don't have to power reset it ever.

[nucleus]

Re: Locating short circuits with bnch psu

I also have similar dc power supply and I can set limits on voltage and current. when it reaches it stays there and can works days without problems. same is for short circuits. so probably your have malfunction or something

[scobie_21]

Re: Locating short circuits with bnch psu

I also have similar dc power supply and I can set limits on voltage and current. when it reaches it stays there and can works days without problems. same is for short circuits. so probably your have malfunction or something

But what about if you are measuring a dead short on a board ? What does it do then ?.


Thanks for the input

[nucleus]

Re: Locating short circuits with bnch psu

But what about if you are measuring a dead short on a board ? What does it do then ?.


Thanks for the input

it reaches limit I set (for example 0.5A), turn on red light that say "I hit the limit" and stays there. thats how it should work every dc power supply I think

[scobie_21]

Re: Locating short circuits with bnch psu

When I adjust the Current without connecting load nothing changes it stays at 0.00A, if I connect say a dc motor the v will go to what I set it to but theres no adjustment on the current it just shows amount of current drawn but is not adjustable