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Old 05-07-2020, 04:20 PM   #20
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Default Re: 20 pin 8A on HP 250 G4 mb - voltage regulator?

Originally Posted by emestee View Post
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.
Thank you for the plain English explanation.
The first Dual Uni-Directional ESD Protection Diode, 3-Pin SOT-23 before the first MLCC is shorting and also the MLCC is shorting. But somehow power is getting to the second Dual Uni-Directional ESD Protection Diode and to the rest of the board. Trying to make sense of the motherboard schematic pdf.

Last edited by nickBcap; 05-07-2020 at 05:12 PM..
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