I am trying to find a short on a motherboard and I have a regulated power supply to use, using this method I will be freezing the board and adding power, Can anyone tell me what current and voltage would be safe to use ? from what I have read on this process you only need to add power for a few second be for the fault shows.

 

put a resistor in series with your load, with a value depending on the current your faulty device woud normally draw. most of the current will be dissapated in the resitor for as long as the short exsists bu you should be able to measure were the short actualy is.

 

If your motherboard is a standard cpu one it needs 3 and ,5,V, so use that setting ideally i would limit the current to 1 amp and slowly wind it up if it's ok, otherwise it will trip.

 

Hi !, My other question is where would you wire the positive and negative to power the motherboard?

 

Follow the original psu inputs, if in doubt.

 

I am trying to find a short on a motherboard

A short on a previously functioning motherboard would be caused by a component and you'd be better off looking for that component using other methods.

 

Here's how I use this method
I solder two AA batteries in series using some wire and alligator clips to make a 3VDC source. Tape them together for convenience and keep them from shorting out to each other.
Use an ohm meter to check across the power filter capacitors to find the circuit with the power-supply short. If you have a short circuit on a power source then you should find several capacitors showing this reduced reading. All the negative leads should be tied together, so this is the ground connection. The same for the positive terminals: positive source.
Freeze a section of the board and apply the battery connections across any of the filter capacitors with a low resistance reading (follow the positive/negative markings on the capacitor).
Note, compressed air for cleaning keyboards etc, turned upside down will also freeze circuitry. One more tip, if you are using freeze spray on an energized circuit, it can damage sensitive electronics (it will also make the circuitry wet after it thaws)

 

If your motherboard is a standard cpu one it needs 3 and ,5,V, so use that setting ideally i would limit the current to 1 amp and slowly wind it up if it's ok, otherwise it will trip.

IR cameras are creeping down in price - but I'm not sure how far. It might be easier to see hot spots than using loads of freezer spray.

The TS needs to make sure the applied voltage doesn't go over spec as well as limiting current draw without tripping off.

Something more versatile than a PC PSU is probably needed.

No current limiting can also burn out buried traces in the multilayer PCB - which is usually terminal, or at least very difficult to track down and patch.