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Old 05-07-2020, 05:12 AM   #19
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Default Re: 20 pin 8A on HP 250 G4 mb - voltage regulator?

Originally Posted by nickBcap View Post
Hi, right by the power charger port is a Dual Uni-Directional ESD Protection Diode which is shorted, I get no O.L. Beep like I do most of the capacitors and the other Dual Uni-Directional ESD Protection Diode near to it.
A beep means the current is running between the probes. In the diode testing mode, a functioning diode will let the current through one way only, and the DMM will show you a voltage drop of 0.4-0.7 volts. If you switch the probes in the opposite direction you should get the O.L. indication, as the diode blocks the current.

If that is not happening (diode rings with probes connected both ways) you are looking at a short. If the DMM shows O.L. with probes connected both ways, you're looking at an open fault. In the former case, whether it is the diode itself that failed will depend on circuits around it. In the latter, you can be pretty much sure it's the diode.

O.L. stands for open loop - the DMM is not supposed to ring when it is displayed.

Last edited by emestee; 05-07-2020 at 05:34 AM..
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