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Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details. |
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1st Feb 2013, 8:30 am | #1 |
Retired Dormant Member
Join Date: Feb 2013
Location: Arlington, Texas, USA
Posts: 1
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Nixie tube calculator repair
I recently purchased a SCM Marchant I portable 8-digit nixie tube calculator. The two leftmost nixie tubes appear not to light up, but if you are in a dark room you can see that they are just barely glowing. The other thing is as you enter numbers the two leftmost digits both change to be the same number as the rightmost digit (the number that you just entered). Another potential clue is that once you fill up the 6 working digits, if you try to add any more numbers (numbers that should go to the last 7th and 8th tubes) the numbers start doubling up in the working tubes.
Any thought on what could be causing this? An IC or a transistor problem? |
7th Feb 2013, 12:07 pm | #2 |
Nonode
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,350
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Re: Nixie tube calculator repair
My Gould frequency counter has nixie tubes. I had a problem about 20 years ago with one or more digits, but forget the exact symptoms.
It was a faulty driver IC. DM8880 or something like that. At the time, I had loads of new Grundig TV panels, and did wonder about replacing the nixies with LEDs and the driver chips for them, but never proceeded. I still have a few new nixies (ZM1000 or something like that) which were a direct replacement for that specified by Grundig for the 6010, 6011 etc. TVs. Les. |
9th Feb 2013, 10:56 pm | #3 |
Heptode
Join Date: Aug 2009
Location: Worthing, Sussex, UK.
Posts: 662
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Re: Nixie tube calculator repair
Looks to be like it is a multiplexed display, and the digit drive / decode circuit has a problem.
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9th Feb 2013, 11:46 pm | #4 |
Dekatron
Join Date: Dec 2004
Location: East Yorkshire, UK.
Posts: 3,990
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Re: Nixie tube calculator repair
A similar fault was discussed on this forum and IIRC tapping moved some loose metal / rust shorting the valve I think.
John. |