Easson DRO - all segments lit (and stay lit) at power on
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  1. #1
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    Default Easson DRO - all segments lit (and stay lit) at power on

    Got an Easson DRO on my manual lathe. Switched on today and instead of it going through it usual startup sequence, every single LED segment lights up and stays lit.

    Tried disconnecting the glass scale plugs and restarting but same result.

    I will remove the back cover and see if there is an internal battery (like on a computer motherboard) that retains memory for position at switch off, but if anyone else has came across this and found a solution, I'd be interested to hear.

    Cheers.

  2. #2
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    Many times numeric readouts were intentionally set to illuminate all the segments for a second or three when power was first turned on. This allowed the operator to observe if any of the segments were burned out, which could cause errors. For instance, with a seven segment display, if the top, horizontal segment was bad, then a 4 and a 9 would display in the same manner.

    It is possible that your DRO has that feature but is getting stuck in the "all segments lit" mode. This is more likely with older equipment with individual ICs in it's circuits. More modern equipment will probably have computer chips doing all the work and such a test, if implemented, would be just part of the programming. If yours is an older design, before micro-processors, then you probably have a bad chip or some other component that provides the timer function for turning this off. As a quick check, you could look for a bad electrolytic capacitor that is not in the power supply section of the circuit. Sometimes these bad capacitors are evident by an expanded look on one or both ends or even some leakage around the wire leads.

    Or you could just replace all the electrolytic capacitors. I have fixed many older pieces of electronic equipment with that strategy. There were even some capacitors made a decade or two ago that were infamous for these failures: many TVs and other items failed due to them.

    This is not typical of a plug or connection problem: those would more likely produce missing segments, not all of them lit up.

  3. #3
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    Thanks EPA.

    Just about to open it up so I'll check for that. I did once fix a "black" TV by replacing a bulged electrolytic capacitor, so I'm glad you reminded me about that.

    This model is ES-10 Lathe. I might have had it a decade or a bit longer.

    Edit:
    All caps look good but there's a PCB rechargeable battery which appears to be leaking and developing "crystal dust" on the outside. The battery voltage is supposed to be 2.4 volts but I measured only 0.6 volts. I'll replace that and see if the problem is fixed.
    Last edited by mancavedweller; 02-15-2020 at 05:27 AM.

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    Easson are low cost Chinese readouts, typical lifespan varies between few month to few years. Basically they start failing after the time to leave feedback on eBay expires. This is one of the reasons we stopped selling those years ago, and started making our own in the USA.
    That crystal dust might have corroded some of the PCB traces nearby, I would check for that too as well as for poor quality solder connections around all ICs.

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    20200220_101453.jpg 20200220_101610.jpg

    Thanks ZSinstruments.

    Just soldered in a new Ni-Mh PCB battery and luckily it fixed it.

    I was surprised to find the casing was not even sealed, just metal to metal. I would have thought such an instrument, in an environment where coolant could be getting splashed about, would be sealed somewhat.

    Guess I've been lucky. I've got this Easson DRO and a Sino DRO on my mill. Had them both over 10 years and this is the first failure. However, I'm just a backyard guy and my machines are not used day in day out, only when I repair or make something.
    Last edited by mancavedweller; 02-19-2020 at 05:40 PM. Reason: Add 2nd photo


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