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EEVblog #1336 – DT71 LCR Tweezer Destructive Teardown + Lab Update

Destructive teardown o nthe Miniware DT71 LCR meter Tweezers Plus a lab move update. Forum: ...

15 comments

  1. Hey Dave, When you flipped it over you were actually looking at CH2 instead of CH3.

  2. Other than looking at the signal coming out of the hybrid and comparing with another channel I’d be inclined to stop. The chips/hybrid are not available so even if you located the issue no fix.

    It would possibly be worth reflowing the chip on the hybrid but other than that no real benefit.

  3. How about powering the chassis up – apply pressure to a few ic packages & connectors while watching the display. I often use a small mirror on my bench for jobs like this. IT could just be a dodgy joint on a bus pin.

    Shame as its a nice little cro.

  4. thw chips that you call ADCs i think that they are not ADCs but analog sample memory. Then the samples are digitized by a few MSPS 9bit ADC(maybe the 5th chip also the 5th chip will maybe used for the triggering).
    So as in the lower sample aquisition there is no problem maybe there is a problem with the analog aquisition memory that maybe loses the charge in the capacitor array…)
    Maybe you can interchange the acquisition chips…
    Also maybe there is problem with the memory or just the digital phosophor circuit… (again memory)
    As the problem goes away from the frontend it cames that there is not an operators false that burned the channel so maybe its just a broken solder…maybe a reflow in the acquisition chip, the adc chip, and the memories will fix the problem
    good luck

  5. Maybe you should measure this differential output signal of CH3 with another scope to know if this issue is before or after that point? 🙂 It should be easy to probe these interconnecting pins.

  6. Hi Dave,

    Maybe time for the hairdryer coolant spray cycle to see if one of the bondwires in the chip has intemmited contacts.

  7. You got four equal channels. So why don’t you power up the device, switch every channel to the same setting and apply an equal signal to all of the BNCs? With a second 4-Channel scope you could observe same solder joint of all four input-modules.

    Even in power-off state one can compare all soldering joints to each other with a Ohm-Meter to GND or Vcc.

  8. Dave, if you connect the input of channel 3 to one of the other channels input, does the interferance also show on the good channel?

  9. Hi,
    It’s possible that each hybrid (or each channel A/D), has its own power regulator. If so, power supply noise maybe?

  10. What exactly does the term ‘hybrid’ mean here?

    • It uses laser trimmed films, parasitic capacitance of traces etc. instead of regular components like 0603 capacitors or resistors. Most circuits are made as a part of ceramic PCB.

  11. Dave — yep, you can get a USB ‘floppy’ module for the thing — http://www.ipcas.com/blog/2012/10/oscilloscope-usb-floppy-emulator-slimline/

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