Dekatron DoHickie #1 glow gets "stuck"

[Terry Kennedy]

I have Dekatron DoHickie #1 (January 2007) from Michael Moorrees (Tortugascuba on eBay, I believe) which uses a Rodan DK23 tube. It stopped being able to do full circles some time ago, but would "bounce" at around 8 o'clock and then swing back counterclockwise to 1 o'clock. I started writing this post 2 days ago, but when I plugged it back in after unplugging it to look at the base, it seemed to be behaving normally. Now it's just stuck bouncing around 1 o'clock, regardless of the mode.

I looked inside to see if it was anything obvious (my first thought on these is always "electrolytic capacitors") but it seems to have been assembled on perfboard and then glued into position, so I just put the cover back on and figured I'd defer to the wisdom of the group.

[gregebert]

I've seen 2 types of spinner circuits: Digital (my preference), and analog (I've never used it).

When I was debugging the spinner in my big clock several years ago (A101 dekatron), I found that a rather large voltage-swing at the cathodes, roughly 20 volts, was needed for reliable operation. I can imagine a dekatron will age over time and have a larger voltage drop, which could eat into the design-margin. Easiest thing to check is measuring the HV supply voltage vs datasheet spec; if that's getting close my first guess is tube-aging effects. If you see a lot of ripple voltage (is this running from a line-voltage tripler ?) then as you said the electrolytic could be wearing-out.

Any chance you can get some scope traces of the cathode pins ? For a simple spinner, all 10 numerical cathodes will be tied together (just like the other 2 sets of shift-cathodes that are tied-together internal to the tube itself).

I'm running my A101 at 500 volts, and 450uA. It's been going 24/7 for over 5 years now with no signs of degradation. It's actually more reliable than the Burroughs 6091 nixies in the clock.

[Terry S]

I'm betting Mike will weigh in, as far as I know he still is a presence here....

[threeneurons]

On Friday, August 17, 2018 at 12:37:16 AM UTC-7, Terry Kennedy wrote:

I have Dekatron DoHickie #1 (January 2007) from Michael Moorrees (Tortugascuba on eBay, I believe) which uses a Rodan DK23 tube....

1st on my list of possibilities, is  a bad connection. That old of a dekatron dohickie, is not the kit (currently being sold), but original version, sold as a complete unit:

Try cleaning the tubes pins with some steel wool, and take a small round file to the socket holes. Try that first, and see what happens.

[orange_glow_fan]

Please be careful using steel wool. Little strands of the wire can get into places that could be fatal to unit itself.  I would use some fine emery type paper on the pins. I would first try a contact cleaner such as Deoxit on both the pins and the socket.

Just trying to help...

[Instrument Resources of America]

Steel wool is absolutely forbidden around any and all electronics labs, production lines, facilities, companies, etc. that I've ever been in, around, or worked for, including my own lab for the last 50 years of my life. Not only because of the what should be the obvious issues around electronic items, but anything which is magnetic, think speakers, microphones, meter movements, motors, solenoids, etc.  If you absolutely have to use that stuff, try to do it outside, and then use compressed air to get rid of any bits and pieces.     Ira.

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[threeneurons]

Steel wool is fine, just for the tube, after its removed from the socket. Make sure to use it away from the circuit, in another room. Wipe the pins and base clean with an alcohol moistened rag afterwards. 

[Terry Kennedy]

On Sunday, August 19, 2018 at 12:46:21 AM UTC-4, threeneurons wrote:

On Friday, August 17, 2018 at 12:37:16 AM UTC-7, Terry Kennedy wrote:

I have Dekatron DoHickie #1 (January 2007) from Michael Moorrees (Tortugascuba on eBay, I believe) which uses a Rodan DK23 tube....

1st on my list of possibilities, is  a bad connection. That old of a dekatron dohickie, is not the kit (currently being sold), but original version, sold as a complete unit:

Mine doesn't look anything like that. I carefully cleaned the tube pins and socket without any change:

 

 

[gregebert]

I think the next step is to poke around with your voltmeter to see if the HV supply is marginal.

Also, if you can get scope captures on the various cathode pins it will give some clues if there is enough of a voltage-difference to get reliable rotation.

Fortunately you should be able to do that from the tube socket.

[threeneurons]

Contact me thru email at threen...@yahoo.com

That is the "original" dohickie ! Hand breadboarded and everything. One off.

The version 1 (round boards) and current version 2A (square red board) kits, came later.