Electronics > Repair
Resistances measurement indicator on PCB
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tooki:
Troubleshooting is a process of elimination. You’ve now eliminated bad resistors as the cause of the problem, so it’s time to investigate other leads. I just don’t want you to think of resistance measurement as a good way to measure things other than resistors. (Yes, it is sometimes useful, but with big caveats.)

Your overheating chip is likely due to one of three things that come to mind:
- it’s getting too much voltage from the power supply (which is why “thou shalt check your power rails” is the first commandment in electronics troubleshooting) or too high voltage on a signal input
- it’s got an excessive load on an output (load drawing too much current)
- the chip has failed and is causing one of those problems to itself

Hopefully those should give you some clues as to what avenues to check out.

And see if you can find a schematic. They’re extremely helpful if available. Even better if there’s an actual service manual…
kraka:
OK
I need a little more help.
The third avenue is completely closed because, i cannot replace this IC. (not technically but physically).
Two much Voltage from the power supply : You do not mean the socket in my wall... ? And the PSU of my PC is a relatively new one, except that all other  parts of my PC is working with no problems.
So if this is the case, there is something on the PCB that cause this high Voltage. The only thing i know is what pins of the PCI is for -12V,+12V,+5V,+3V,Ground,IOPWR. But i do not know, exactly, how to use them to trace the current flow. I have a device by which i can "inject" Volts to the PCI, but from there, except from the connections, i am not sure how to continue to check if the power rails have a problem. I never did it.
For the excessive load on an output (load drawing too much current), what do you mean with load ? A device inside the IC (diode, resistor etc) or a device outside it, or both ? If it is a device outside of the IC, will it be heated up , too ?
 
I have the schematic of this IC

807:
It will help if you gave us more information.

What is the PCI card? Make/model?

What is the number on the IC that's getting hot?

Is it getting too hot to touch, or just warm?

You say that you have the schematic of the IC. Measure the voltage on the supply pin. Is it within spec?
kraka:
1) A friend gave me an identical PCI card which is functional, and the measurement on both resistors (marked 4.7K) really gives 4.7K.
 2) After removing the overheated PLD  (on the faulty PCI card), I remeasured these two resistors and they both give 4.7K.

 Can we draw any conclusions?
tooki:
Not really. You were asked a bunch of specific questions and you ignored them. We are not clairvoyant. A couple of resistance measurements tell us nothing.

The comparison between good and bad board simply gives you an idea of where the problem may or may not be. Where you get the same result on both boards, the problem likely is not.
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