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I am using Fluke multimeter and trying fix electronic circuit. In diode mode fluke docs, telling briefly explained how to test the durability and accuracy of diodes. The test usually runs when I touch the probes on the circuit to the anode and cathode of the diode. and it shows a value of 0.6 volts on one side and the OL value appears when I change the probes side.

but things are not going as usual. in a different electronic board, When I touch the probes to the diode again it writes 0.6 volts. but when I change the location of the probe slowly and I encounter an ever-increasing voltage value. I wonder what they might have connected on the circuit in parallel with the diode, or if we assume that the diode is intact, what short circuit might have been in the circuit. do you have any idea

Whatever possibility I tried out of circuit, on the one hand a constant voltage, on the other hand slowly and continuously increasing voltage when I change the place of the probe, I could not design. Why do you think I see a constantly increasing voltage value when I change the probes?

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    \$\begingroup\$ What do you mean by "change the location of probe"? Do you place the probe on a different pin? \$\endgroup\$
    – jusaca
    Mar 25, 2020 at 8:23
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    \$\begingroup\$ Are you comparing exactly the same electronic boards? Note you cannot not expect the same measurement behaviour from components when mounted on a PCB. The the component is connected to other components on the PCB, it will influence the measurement. \$\endgroup\$
    – Huisman
    Mar 25, 2020 at 9:00
  • \$\begingroup\$ @jusaca on the same board, same diode, placing the probes anode to cathode, cathode to anode \$\endgroup\$
    – mehmet
    Mar 25, 2020 at 9:32
  • \$\begingroup\$ @Huisman I am curious about the diode measurement, on the one hand, we have to see a constant voltage like 0.6, on the other hand, Why do I see a constantly increasing value when I instead of to see the OL value \$\endgroup\$
    – mehmet
    Mar 25, 2020 at 9:37
  • \$\begingroup\$ @mehmet - Hi, Please add extra details into the question, to make your exact testing procedure clear. For example, you said: "Whatever possibility I tried out of circuit" - that is not clear: Are you testing these diodes out-of-circuit (i.e. with at least one terminal disconnected from the rest of any circuit) - yes or no? If the answer is "no" then you should not expect to see the usual behaviour, as when testing out-of-circuit. Other components change the test result. Is this related to your repair question on boards without schematics? \$\endgroup\$
    – SamGibson
    Mar 25, 2020 at 16:12

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I wonder what they might have connected on the circuit in parallel with the diode

Capacitor or RC circuit is connected in parallel with the diode.

Why do you think I see a constantly increasing voltage value when I change the probes?

Diode measurement operates using small current. It takes time to charge the capacitor, that is why you see such behavior.

By the way I tested with my Fluke, added 1000uF capacitor (first pick up) in parallel to diode and indeed it takes time until reverse-diode measurement shows open circuit.

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