Nixie Clock Issue - Need Suggestions on how to repair

Discussion in 'Technical Repair' started by seanfox, Mar 21, 2016.

  1. seanfox

    Thread Starter New Member

    Mar 21, 2016
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    I assembled the clock pictured recently as directed and upon completion I found an issue. The tube located in the far right hour position didn't come on but the rest did and the clock otherwise operates normally. I took some voltage readings and based on my limited knowledge I think the tube maybe defective however I am looking for some guidance here on next steps I should take to determine root cause.

    Thanks for the assistance.
    Clock 4.png Clock 3.png Clock 2.png Clock 1.png
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    It's possible that either the common connection is missing or the gas has escaped. Have you compared the voltages on the pins with those present on a working tube?

    Do you have the schematic?
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Have you got a circuit, also have you swapped tubes around, does it light up then?
     
  4. magnet18

    Senior Member

    Dec 22, 2010
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    Ditto for needing a schematic, i assume that list of voltages in the 120s followed by 56 is the anode voltage?

    The first thing I would try is desoldering the tube anode pin and seeing what voltage you get there

    It's either the tube is bad, the tube isn't getting good anode voltage, or the cathodes aren't getting pulled low as expected
     
  5. seanfox

    Thread Starter New Member

    Mar 21, 2016
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    Thanks for all the replies!! I will try to answer each question.
    1. Schematic, yes, I have attached it. Password to open is: emiliukas789654321
    2. "It's possible that either the common connection is missing or the gas has escaped. Have you compared the voltages on the pins with those present on a working tube?" Yes and the only difference I have found is the common on most of the tubes are 120v to 127v except for the one that isn't working which is showing 56v. I lifted the 10K resister to tubes 5 (working) and 6 (not working) and no change on the voltage coming from the optical isolator but oddly enough I get a voltage on the anode of tube 6 were on tube 5 it's zero...
    3. "Have you got a circuit, also have you swapped tubes around, does it light up then?" I suspect that the tube is bad but don't want to remove it until I am sure because each time I remove a component I am heating up the board.
    4. "The first thing I would try is de-soldering the tube anode pin and seeing what voltage you get there" I think this is the same as lifting the 10K resistor, so the readings are above.
     
  6. seanfox

    Thread Starter New Member

    Mar 21, 2016
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    Any suggestions?
     
  7. Dodgydave

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    Jun 22, 2012
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    Looks like its a multiplexed display, on the Cathodes, so its the common Anode supply that must be at fault, check the Anode resistor and opto-coupler T1,R11 on the faulty tube.

    You could swap the hour and x10 hour pins on the the pic chip to see if its the tube.
     
  8. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Are the optocoupler all in working order?
    Are the version jumpers set correctly?

    seanfox_nixie_clock_jumper_comment.png

    Bertus
     
  9. RichardO

    Well-Known Member

    May 4, 2013
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    Or swap the connection of the 10K resistors (R11 and R12?) to the tubes.
     
  10. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    No, those are solder pads on the PCB to set the version.

    seanfox_nixie_clock_jumper_picture.png

    Bertus
     
  11. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    I think the neons are labelled DOTBULB.
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    You ever tried unsoldering one of those?!!!!!
     
  13. magnet18

    Senior Member

    Dec 22, 2010
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    Almost impossible with an iron, your only hope is pulling out one lead at a time with needle nose pliers, heat gun gets the job done but expect to destroy something else in the process :p


    Props to the designer of this clock, the IN-14 is my favorite nixie :D

    [EDIT]
    Nevermind, version jumpers appear to only affect little neons.

    Check that the opto-coupler is getting signal, it's either the signal to the optocoupler, the optocoupler itself, R11, or the tube.(Or a PCB issue, though unlikely in this case)
    My money is the tube
     
    Last edited: Mar 22, 2016
  14. seanfox

    Thread Starter New Member

    Mar 21, 2016
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    Thanks all for the replies, I think I am going to go with the tube being at fault because I did try routing the output of R12 to the tube that isn't lighting and nothing. I did validate the opto-coupler was good by building a test circuit, removing the coupler and testing it.

    I have a leister hot air gun so no prob, heating up the joints to remove but rather only do this one time. Going to order another tube(instead of swapping), they are cheap enough but won't be here for a few weeks. BTW the place I brought this from, no help or support so thanks for all your support here. I will let you know the outcome.
     
  15. seanfox

    Thread Starter New Member

    Mar 21, 2016
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    So I just placed the order for the tube however I am still a little leery this is the problem (or only problem). Reason is that I connected R11 to H2 and nothing. Furthermore even with T1 Pin 4 lifted I still get only 55v from Pin 4 to ground were as I am getting 171v to ground on T2 Pin 4.

    I show 1.2v across Pin 1 & 2 for T1. T2, 3, & 4 it's millivolts and for T6 & 7 it's .95v. So I am a bit lost to why the variance and if the input has something to do with only getting 55v on the output... BTW Pin 3 is 180v which matches across all Pin 3's for the opto-couplers...
     
  16. magnet18

    Senior Member

    Dec 22, 2010
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    I advise against hot air gun, clip the leads to remove the tube and then desolder remnants one by one so you don't blister the soldermask off of the PCB (done it before)

    As for your optocouplers, are using a DC voltage reading on them while they are being rapidly switched on and off by the MCU?
    If so you aren't getting any useful values
     
  17. seanfox

    Thread Starter New Member

    Mar 21, 2016
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    noted on the hot air gun, will go the safe route. I honestly haven't worked much with the opto-couplers so someone else smarter than me would need to advise. I think you maybe right about it thus why there are no useful readings...
     
  18. seanfox

    Thread Starter New Member

    Mar 21, 2016
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    Well, good news and bad news. Good news is that the tube was in fact bad, pin 1 was showing 40ohms between it and the common and when I replaced it with the new tube, everything stated to work.....however after about 30 minutes, the clock starts to freak out. I have attached several videos. I cut them into clips for ease of viewing, this all occurred over a 25min period. In some cases powering off the clock and back on recovers it (temporarily) however in most cases I have to pull the PIC to reset it. I think this is due to residual power is being held in the caps so just turning it off and on doesn't always work.

    I was able to use an oscilloscope and the 4 data lines going between the PIC and IC4 show a nice square wave when it's working correctly however when the tubes have completely dimmed out as you will see on the last video, there is no signal.

    I think the PIC processor is flakey but wanted input from this forum. I assume I can't just buy any PIC and I will have to get one from the guy I bought the clock from since it's programed for this purpose....





     
    Last edited: Apr 3, 2016
  19. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    Have you checked the power-supply voltages when this problem occurs?
     
  20. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You can temporarily short out C8, or pull pin 4 to ground for a master reset. If the pic is in a socket what signals are you getting if you swap the pic outputs, or lift the pin out of the socket?

    It seems to reset to zero at 06:47?
     
    Last edited: Apr 4, 2016
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