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  1. #1
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    Wish to repair Tenma 72-8155 capactiance meter

    Hi,
    Today I tried to measure the capacitance of a 100n ceramic cap on an unpowered PCB that had not been powered for several days. In service this capacitor has 339V pk on it.

    I used a Tenma 72-8155 capacitance meter....
    https://uk.farnell.com/tenma/72-8155...8mm/dp/1283643

    There was a “click” type sound as I probed the capacitor with the 72-8155 meter….which I guess was some excess charge on the capacitor discharging through the meter.
    After this, the meter would not work.
    I am surprised that the capacitance range doesn’t have overvoltage protection on it.
    I wonder if anyone has a schematic of this meter?.... because maybe its just a crowbar circuit that has gone and blown a fuse.

    Seriously, capacitors often have excess voltage left on them and its so easy to forget…so I’m amazed the meter was not protected against this.

    Now neither the R, L or C aspect of the meter works..its totally dead.
    How may i repair?

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  2. #2
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    Re: Wish to repair Tenma 72-8155 capactiance meter

    I would think it highly unlikely that significant charge would still exist after several days, especially in-circuit, more likely it 'just' broke and was a coincidence.
    Tenma should provide a repair service and may help with schematics if you want to repair it yourself. I can't confirm as I have no Tenma equipment here but experience with other manufacturers teaches me they are generally very helpful.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.


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  3. #3
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    Re: Wish to repair Tenma 72-8155 capactiance meter

    On the website posted there is a 2 star rating by a single user...broke after 6 months...
    In the user guide pdf:
    Please read these instructions carefully before use and retain for future reference.
    • Please operate according to this manual, otherwise the protection provided by the device will be impaired or fail.
    • Check the test leads, probe and case insulation condition before using. If you find any breakage, damage or abnormality, or you consider the device is broken, stop using the device immediately.
    • When using the test probes, keep your fingers behind the finger protection rings.
    • Ensure all inputs are less than the range selected otherwise it may cause electrical shock or meter damage.
    • Do not apply voltage to the meter.
    • Disconnect circuit power and discharge all high-voltage capacitors before testing resistance, continuity, capacitance or diodes.
    • Do not use the meter with the back cover removed.
    • Do not adjust the range selector during measurement.
    • Replace the batteries as soon as the low battery indicator appears on the display.
    • Remove dead batteries from the meter or if it is not going to be used for a long time.
    • Never mix old and new batteries together, or different types of batteries.
    • Never dispose of batteries in a fire, or attempt to recharge ordinary batteries.
    • Before replacing the battery, turn off the meter and disconnect all the test probes.
    • To prolong battery life turn off the meter after use..
    The three highlighted in red are why I like auto-ranging meters.


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