A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post...

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In my field of arcade repairs we run into older jukeboxes - one  
particular model which uses the 2D21 tube and was from about 1954.

I have the spec sheet here:

https://www.flippers.com/pdfs/2D21_Thyratron_tube.pdf

It would be fun to make a solid state replacement for it as nothing  
seems to exist. These tubes are still available from several sources,  
but they get wonky with age.

Being able to simply wire in a TRIAC or SCR (with appropriate bits of  
electronic glue) to remove this tube from the suspect list when  
servicing this classic Seeburg V200 jukebox would simplify future  
servicing. I always like to make things easier for the next tech to work  
on machines that passed through my shop...

I should point out that Seeburg only used these 2D21s (three 2D21s used)  
on their very first control center for their Tormat (200 x magnetic  
cores) memory and dropped it like a hot potato. There were numerous  
service bulletins culminating in the factory providing a low cost  
replacement for the control centers that used 2D21s (three of these) and  
the replacement used a single 2050 tube and was a very reliable design.  
Not everyone took advantage of the program and all these replacement  
were used up long, long ago.

John :-#)#

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Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/2021 1:28 PM, John Robertson wrote:
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What happens to them as they age? is that with respect to the unused NOS  
types?

I was under the impression that small-signal gas thyratrons were very  
reliable in service. They're much less temperature sensitive in service  
than solid state devices, at least. If you blast a relaxation oscillator  
made with a 2D21 with cold spray it barely drifts.

Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 2021/04/21 10:48 a.m., bitrex wrote:
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The 2D21 tubes become erratic, sometimes they respond, sometimes they  
are slow (the solenoid grumbles as it sluggishly engages), and sometimes  
they just ignore the control signal. Yet these tubes test OK on my  
mutual conductance tube checker (of course).

John :-#)#

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Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/2021 1:53 PM, John Robertson wrote:
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Maybe the hydrogen is out-gassing thru the glass over time?

Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/2021 1:53 PM, John Robertson wrote:
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The tube tester can test for conductance from thermionic emission but  
IDK if it can test for the conductance when the tube is operating in the  
ionization-cascade mode.

Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)

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A tube tester may not apply enough voltage or current capability to
fire the gas, so would miss a problem with ionization.

What's the Gm of a thyratron anyhow?

One could build a simple thyratron tester.


Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/2021 2:18 PM, John Larkin wrote:
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Thyratron anode conductance is grid current-controlled when in the  
ionization mode, you can read off the parameters from fig 2 of the 2D21  
datasheet. For grid 1 voltages between about -1 and -5 volts and Ib  
between 25 and 200 mA it's vaguely linear at about 50mA per 1 mA.

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Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/2021 1:53 PM, John Robertson wrote:
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Hydrogen diffusion through thin glass within tube-like operating  
temperatures, where the gas is in thermal equilibrium with the glass and  
the mean free path is >> glass thickness is dominated by e^(-1/T), so if  
hydrogen outgassing is causing the erratic behavior whether the tube  
envelope temperature is run before the "knee" or after may have a lot to  
do with the expected service life.

Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/2021 2:50 PM, bitrex wrote:
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I may have the pac-mans backwards there don't quote me on that. :)

Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
I may have a few of either floating about in my junk boxes. If so, I would be glad to send all that I  have to you as I have no discernable use for them. I seem to remember those numbers,  

Gratis, of course. I will let you know.

Peter Wieck  
Melrose Park, PA  

Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
wrote:

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Got a schematic? It might be easy.


Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/2021 2:14 PM, John Larkin wrote:
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The 1954 gear was probably designed to run on old-timey line voltage of  
~110 AC. Dialing back the heater voltage on the thyratrons to compensate  
for higher modern AC supply voltage might extend their life.

Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 2021/04/21 11:19 a.m., bitrex wrote:
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This controlled a solenoid at around 24VAC or regulated (0A2 = -150VDC)  
power supply for the tormat write-in and readout circuits.

John :-#)#

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Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/2021 3:47 PM, John Robertson wrote:
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I can't find a solid reference on what the gas in the 2D21 is, anyway.  
Only few references from the time period I can find don't agree, one  
paper says it's hydrogen:

<https://books.google.com/books?id=IdB5E4STz5kC&lpg=RA5-PA37&ots=T6ZN06aJWy&dq=hydrogen%20in%202d21&pg=RA5-PA37#v=onepage&q=hydrogen%20in%202d21&f=false

Another says it's xenon:

<http://phylab.fudan.edu.cn/lib/exe/fetch.php?media=exp:ajp000701.pdf





Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/22/2021 1:07 AM, bitrex wrote:
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Maybe a mixture of stuff.


Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/22/2021 1:07 AM, bitrex wrote:
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I think it must be xenon, the first one is just wrong


Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/21 11:43 PM, bitrex wrote:
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Nah, they are just xenon-phobic :-)


Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)

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  110 VAC went away at the beginning of the 20th century.  By 1950  
120 Volts was the standard.  The MONIKER remained, but the voltage  
has been 120 VAC for a VERY long time.

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  The line voltage was already 120 Volts by then.  You need a  
remedial electrical system / electronics industry history course.

  Or maybe you would simply develop enough Internet skills to know  
how to use google properly.

Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/21 8:31 PM, snipped-for-privacy@decadence.org wrote:
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We go through this over and over again on the antique radio news
group.
  110, 117, 120 = 120 vac


--  
"I am a river to my people."
Jeff-1.0
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Re: A solid state replacement for the lowly 2D21 Thyratron tube...(sorry for the On-Topic post!)
On 4/21/2021 10:42 PM, Fox's Mercantile wrote:
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I'm hearing that DLUNU would like to take responsibility for this  
project and I think he's the best qualified based on his rebuttal. I  
mean it's in his name. "NumeroUno"

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