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Schottky diode behavior question
Schottky diode behavior question
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Old 9th September 2021, 11:31 PM   #1
ranshdow is offline ranshdow  United States
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Join Date: Jul 2020
Location: SF bay area
Default Schottky diode behavior question

Hi, I'm trying to repair a friend's cheap USB capable turntable. It's powered by a 14V wall wart and has a lot of SMD electronics inside it.



I found an apparent Schottky diode (SMD component with a cathode band marked as SS34, according to Vishay has a 40V max DC blocking voltage) with some odd behavior- I can measure single digit resistance across it in either direction using an ohmmeter. When the unit is receiving power from the wall wart I can't measure a potential difference across the diode, though I can measure about 14V from another, nearby diode. I tried shorting across the suspect diode with a normal 1N4004 diode but that didn't help (not surprising given it's acting like a wire on it's own).



My questions are 1) this is bad behavior for a Schottky diode, right? and 2) is there any reasonable circuit design that would have single-digit resistance in both directions in parallel with a Schottky diode? I have no schematic and wasn't able to find one online.


Trying to decide whether it's worth it to try and replace the Schottky or not. Thanks for reading!
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Old 9th September 2021, 11:54 PM   #2
rayma is online now rayma  United States
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Take it out of circuit for all testing. It will likely behave differently then.
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Old 10th September 2021, 04:49 AM   #3
Enzo is offline Enzo  United States
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Location: Lansing, Michigan
Um... Your diode reads low resistance both ways, and no voltage drops across it? Sure sounds like it is shorted so far.
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Old 10th September 2021, 10:42 PM   #4
egellings is offline egellings  United States
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I get the impression it's shorted.
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Old 12th September 2021, 05:56 PM   #5
ranshdow is offline ranshdow  United States
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Join Date: Jul 2020
Location: SF bay area
Thanks everyone. The turntable’s owner will try and return it so I don’t have permission for surgery.
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