Injecting voltages into a line...can someone provide instruction pls

[bruce1129]

i would like to inject voltages into a line, i know that you keep it at or under the voltage for that line...
is there a certain type of wire used for this or ? also, im assuming you pick a point on the board, put your positive on it, negative on ground?
do i have to adjust voltage and amps on my power supply as well or just voltage?

 

[peterfixit]

louis uses a single pair of ethernet cable, put it in where you need it and negative on a screw hole, voltage same, amps what you are comfortable, personally I would use infinite amps, provided its not on a line thats directly connected to the cpu or mcp

 

[bruce1129]

ok thank you for the quick response

 

[2informaticos]

Always set current to max.
The short will take the current depending on its value and voltage injected (Ohm's law).
If you set lower current, the lab supply will go in protection mode.
Cheaper ones will still show you high current, but will not really inject, as the protection has been triggered.
I you want to inject in the main power rail, check first if any high-side MOSFET is not shorted.
Imagine what will happen injecting 5-15V there with such MOSFET shorted on the CPU, or PCH secondary supply...

 

[drewrox2009]

I learned today what will happen injecting 12v into ppbus_g3h with some serious issues on the board. ppbus_g3h was pulled down to 4v and in trying to find the short i burned up the cpu. Luckily this was an old motherboard that belonged to me and was just trying to kill time and see if i could get it to work. Learn from my mistakes.

 

[dukefawks]

The CPU was dead to start with, but you should always start with low voltage and monitor current.