Nixie tube calculator repair - UK Vintage Radio Repair and Restoration Discussion Forum

Sean4star · 1st Feb 2013, 8:30 am

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?

MotorBikeLes · 7th Feb 2013, 12:07 pm

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.

JohnBHanson · 9th Feb 2013, 10:56 pm

Looks to be like it is a multiplexed display, and the digit drive / decode circuit has a problem.

60 oldjohn · 9th Feb 2013, 11:46 pm

A similar fault was discussed on this forum and IIRC tapping moved some loose metal / rust shorting the valve I think.
John.

1st Feb 2013, 8:30 am	#1
Sean4star Retired Dormant Member Join Date: Feb 2013 Location: Arlington, Texas, USA Posts: 1	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
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	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
JohnBHanson Heptode Join Date: Aug 2009 Location: Worthing, Sussex, UK. Posts: 661	Re: Nixie tube calculator repair Looks to be like it is a multiplexed display, and the digit drive / decode circuit has a problem.

9th Feb 2013, 11:46 pm	#4
60 oldjohn Dekatron Join Date: Dec 2004 Location: East Yorkshire, UK. Posts: 3,987	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.