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

[John Robertson]

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 :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

[bitrex]

On 4/21/2021 1:28 PM, John Robertson wrote:
> 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 :-#)#
>

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.

[Peter W.]

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

[John Robertson]

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).

[bitrex]

Maybe the hydrogen is out-gassing thru the glass over time?

[bitrex]

On 4/21/2021 1:53 PM, John Robertson wrote:

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.

[John Larkin]

On Wed, 21 Apr 2021 10:28:02 -0700, John Robertson <sp...@flippers.com>
wrote:

>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 :-#)#

Got a schematic? It might be easy.

[John Larkin]

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.

[bitrex]

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.

[bitrex]

On 4/21/2021 1:53 PM, John Robertson wrote:

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.

[bitrex]

I may have the pac-mans backwards there don't quote me on that. :)

[bitrex]

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.

[John Robertson]

A fairly recent scan (not tidied up) of my files section for the V200
Control Center:

https://www.flippers.com/pdfs/Seeburg_V200_Pg_5113-5143_B&W.pdf

Relevant schematic is on page 5128 (pg 16 or the PDF).

The first control center is the original TSR1-L6, later it shows the
replacement control center the TSR3-L6.

You can ignore the stepper section, that is the interface to allow booth
boxes (called Wall Boxes in the industry) - but it doesn't matter unless
one is using those remote selectors...

Thanks for looking at this!

[John Robertson]

This controlled a solenoid at around 24VAC or regulated (0A2 = -150VDC)
power supply for the tormat write-in and readout circuits.

[ohg...@gmail.com]

On Wednesday, April 21, 2021 at 1:28:10 PM UTC-4, John Robertson wrote:
> 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.

Designing a workaround would be easier from the standpoint of seeing exactly how it's wired in a circuit as opposed to making a general sub for that tube. Is there a schematic on-line anywhere?

[Spehro Pefhany]

On Wed, 21 Apr 2021 12:44:37 -0700, John Robertson <sp...@flippers.com>

A thyratron is similar to an SCR, maybe a sensitive-gate type like
2N5064 could be made to work. This one is apparently Xenon-filled.

http://www.r-type.org/pdfs/2d21.pdf

https://www.mouser.ca/datasheet/2/308/2N5060_D-110409.pdf

I don't have the relationships of the thyratron grids in my head
though, never designed with one (I once fixed a spot welder that had
an enormous lethal-looking high voltage thyratron tube (cap on the
top) and a giant step-down transformer to give the kA pulse).
Hardly touched vacuum tubes after HS, for that matter.
--
Best regards,
Spehro Pefhany

[bitrex]

Between the forces of good and the Evil Empire they must have made
bajillions of these things. Why OP not buy a gross from Russia? Just
sitting in their boxes in a dry environment the shelf life might be
measured in centuries.

<https://www.ebay.com/itm/274314016219?hash=item3fde63b5db:g:T38AAOSwgOpeqBXp>

[John Robertson]

Where's the fun in that? As I said, I know I can still get new tubes.
The problem is the system doesn't work well...

[Edward Rawde]

"John Robertson" <sp...@flippers.com> wrote in message
news:EKmdnXgYE4CpWx39...@giganews.com...
.....

>>
>> Between the forces of good and the Evil Empire they must have made
>> bajillions of these things. Why OP not buy a gross from Russia? Just
>> sitting in their boxes in a dry environment the shelf life might be
>> measured in centuries.
>>
>> <https://www.ebay.com/itm/274314016219?hash=item3fde63b5db:g:T38AAOSwgOpeqBXp>
>
> Where's the fun in that? As I said, I know I can still get new tubes. The
> problem is the system doesn't work well...

I had a look at the pdf and the schematic looks like a typical work of art
from that era.

So you could probably get a solid state equivalent designed if you wanted to
pay a designer with the necessary experience to do it.
I'm not offering but I'd need the hardware in the same room as me to have
any chance.

[DecadentLinux...@decadence.org]

bitrex <us...@example.net> wrote in
news:X0_fI.33919$wd1....@fx41.iad:

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.

> Dialing back the heater voltage on the
> thyratrons to compensate for higher modern AC supply voltage might
> extend their life.

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.

[Fox's Mercantile]

On 4/21/21 8:31 PM, DecadentLinux...@decadence.org wrote:
> 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.

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
WA6FWi
http:foxsmercantile.com

[bitrex]

But why when there are so many antiques available here to correct me

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

Maybe you are so cranky all the time because yous are really easy to
manipulate into working for free.

[bitrex]

On 4/21/2021 10:42 PM, Fox's Mercantile wrote:
> On 4/21/21 8:31 PM, DecadentLinux...@decadence.org wrote:
>> 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.
>
> We go through this over and over again on the antique radio news
> group.
> 110, 117, 120 = 120 vac
>
>

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"

[DecadentLinux...@decadence.org]

bitrex <us...@example.net> wrote in news:O36gI.7688$mO3....@fx09.iad:

In case you missed it, he was backing me up.

[bitrex]

I would hope so! You're team lead, now

[bitrex]

There's this patent from '66 that describes a solid-state thyratron
replacement:

<https://patentimages.storage.googleapis.com/42/6a/0d/6e35c415a3f0e0/US3293449.pdf>

It uses a couple of SCRs. It's to replace high-power thyratrons but I
don't see why it couldn't be scaled-down.

[bitrex]

On 4/21/2021 8:41 PM, John Robertson wrote:

What's a "Wall-o-Matic"?

[bitrex]

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>

[bitrex]

Maybe a mixture of stuff.

[bitrex]

On 4/22/2021 1:07 AM, bitrex wrote:

I think it must be xenon, the first one is just wrong

[DecadentLinux...@decadence.org]

bitrex <us...@example.net> wrote in
news:mh6gI.266012$DJ2....@fx42.iad:

No... According to the LarkinPunk, I am a mere "technician" who
"hates the magic" of engineers.

[piglet]

On 22/04/2021 5:00 am, bitrex wrote:
>
> There's this patent from '66 that describes a solid-state thyratron
> replacement:
>
> <https://patentimages.storage.googleapis.com/42/6a/0d/6e35c415a3f0e0/US3293449.pdf>
>
>
> It uses a couple of SCRs. It's to replace high-power thyratrons but I
> don't see why it couldn't be scaled-down.

Thanks Bitrex, that patent even mentions a tunnel diode and UJT which
are now very exotic devices. The struggle was to emulate the high
impedance thyratron grid. It seems to me (I have never seen a thyratron)
that a modern depletion mode mosfet would make a good front-end to a SCR
in that a negative grid bias is required to keep the device
non-conducting (if I understand thyratrons correctly).

Here is a conceptual sketch:

<https://www.dropbox.com/s/al1b8hj07i7jfpq/SED_Thyratron_Idea.pdf?dl=0>

Possible fets could be BSS126 or LND150 and SCR with sensitive gates
X0402NF or BT149G.

piglet

[bitrex]

On 4/22/2021 5:04 AM, piglet wrote:
> On 22/04/2021 5:00 am, bitrex wrote:
>>
>> There's this patent from '66 that describes a solid-state thyratron
>> replacement:
>>
>> <https://patentimages.storage.googleapis.com/42/6a/0d/6e35c415a3f0e0/US3293449.pdf>
>>
>>
>> It uses a couple of SCRs. It's to replace high-power thyratrons but I
>> don't see why it couldn't be scaled-down.
>
> Thanks Bitrex, that patent even mentions a tunnel diode and UJT which
> are now very exotic devices. The struggle was to emulate the high
> impedance thyratron grid. It seems to me (I have never seen a thyratron)
> that a modern depletion mode mosfet would make a good front-end to a SCR
> in that a negative grid bias is required to keep the device
> non-conducting (if I understand thyratrons correctly).

Well Fig 2 in the patent doesn't look like it requires anything exotic,
the exotics look to be included in the "further embodiment of the invention"

> Here is a conceptual sketch:
>
> <https://www.dropbox.com/s/al1b8hj07i7jfpq/SED_Thyratron_Idea.pdf?dl=0>
>
> Possible fets could be BSS126 or LND150 and SCR with sensitive gates
> X0402NF or BT149G.
>
> piglet

Yeah, depletion mode MOSFET seems a plausible modern take on it. Only
thing is a real gas thyratron the anode current is controlled by the
control grid current when it's in the low impedance ionized state. In
many switching applications though I expect this doesn't matter too much
it doesn't matter what the impedance is in that state exactly, just so
long as it's low enough to reliably fire the relay or whatever.

And there doesn't need to be an analog to the screen grid, when the tube
is used like a switch to ground it's usually connected to the cathode
and just prevents the thyratron from firing until the positive-going
pulse on the control grid is seen. You can see in a 2D21 a box-like
structure surrounding all the other electrodes and I believe that whole
structure is connected to the screen grid pin.

[bitrex]

Sounds like you have something to prove. Sometimes when I'm helping the
little ol' lady in the library do her taxes some kid shows up with
something to prove too and is like "No dummy you're doing that all
wrong" and then I say "Okay.." and hand the job off directly to him, let
him spend the next two hours with her while I go about my day. I'm not
going to fight him on it he is the white-knight expert who has appeared
in our time of most need. And it makes Ethel very happy!

But that's interesting about the line voltage it seems to be a common
misconception and 1954 was a long time before I was born. In any case my
thoughts on the 2D21-dying issue have changed it's not hydrogen-filled
it's probably primarily xenon. Hydrogen-filled thyratrons are more
temperature-sensitive to both the temperature of the heater and
temperature of the glass if they're too hot all the hydrogen tries to
run away or react with the hot cathode. Obviously xenon won't react with
the internal elements or the getter but it can still be absorbed by the
glass or escape where the pins come in.

So I still think the reason they end up malfunctioning in service is
that the gas is escaping or being absorbed by the glass and reducing the
operating temperature of the cathode may extend their life.

[bitrex]

On 4/22/2021 9:21 AM, bitrex wrote:
> On 4/22/2021 5:04 AM, piglet wrote:
>> On 22/04/2021 5:00 am, bitrex wrote:
>>>
>>> There's this patent from '66 that describes a solid-state thyratron
>>> replacement:
>>>
>>> <https://patentimages.storage.googleapis.com/42/6a/0d/6e35c415a3f0e0/US3293449.pdf>
>>>
>>>
>>> It uses a couple of SCRs. It's to replace high-power thyratrons but I
>>> don't see why it couldn't be scaled-down.
>>
>> Thanks Bitrex, that patent even mentions a tunnel diode and UJT which
>> are now very exotic devices. The struggle was to emulate the high
>> impedance thyratron grid. It seems to me (I have never seen a
>> thyratron) that a modern depletion mode mosfet would make a good
>> front-end to a SCR in that a negative grid bias is required to keep
>> the device non-conducting (if I understand thyratrons correctly).
>
> Well Fig 2 in the patent doesn't look like it requires anything exotic,
> the exotics look to be included in the "further embodiment of the
> invention"

Oh okay I see what you're saying, instead of using a high-impedance SCR
as the first element in a two-SCR pair there are better devices to solve
that "struggle" of the inventor, now.

[jla...@highlandsniptechnology.com]

On Wed, 21 Apr 2021 12:44:37 -0700, John Robertson <sp...@flippers.com>

Yikes. The tube pins all go to off-page connectors, so it's not easy.



--

John Larkin Highland Technology, Inc

The best designs are necessarily accidental.

[amdx]

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

[John Robertson]

Commonly called "Booth Boxes" or "Wall-Boxes" these used to be (and
still are in a few places) jukebox remote controls that displayed a list
of the songs available and a coin acceptor and push button system to
make your remote selection on the in-house jukebox.

Not unlike a dial phone in many ways - used a pair of steppers - one for
the letter (up to twenty) and a second for the number (up to ten) to
make a selection of one of up to two hundred songs.

Some photos here:

https://www.smbaker.com/converting-a-seeburg-3wa-wallbox-into-a-remote-for-a-modern-music-player

[John Robertson]

The off page connections are mostly switches. I'll find the wiring
layout diagram and post it a bit later...

[John Robertson]

From the service manual - the sequence of operations guide:

https://www.flippers.com/pdfs/Seeburg_V200_Pg_139-154_Colour.pdf

[John Robertson]

Not unlike He-Ne laser tubes out-gassing He through the glass and
failing back when LaserDisk players were somewhat popular (80s).

[John Robertson]

Yes, that might work - at least as a starting point. Need to poke at the
values a bit and keep the patent design in mind too - I suspect the
sensitive gate SCR didn't exist then.

Thanks!

[bitrex]

On 4/22/2021 1:53 PM, John Robertson wrote:
> On 2021/04/22 2:04 a.m., piglet wrote:
>> On 22/04/2021 5:00 am, bitrex wrote:
>>>
>>> There's this patent from '66 that describes a solid-state thyratron
>>> replacement:
>>>
>>> <https://patentimages.storage.googleapis.com/42/6a/0d/6e35c415a3f0e0/US3293449.pdf>
>>>
>>>
>>> It uses a couple of SCRs. It's to replace high-power thyratrons but I
>>> don't see why it couldn't be scaled-down.
>>
>> Thanks Bitrex, that patent even mentions a tunnel diode and UJT which
>> are now very exotic devices. The struggle was to emulate the high
>> impedance thyratron grid. It seems to me (I have never seen a
>> thyratron) that a modern depletion mode mosfet would make a good
>> front-end to a SCR in that a negative grid bias is required to keep
>> the device non-conducting (if I understand thyratrons correctly).
>>
>> Here is a conceptual sketch:
>>
>> <https://www.dropbox.com/s/al1b8hj07i7jfpq/SED_Thyratron_Idea.pdf?dl=0>
>>
>> Possible fets could be BSS126 or LND150 and SCR with sensitive gates
>> X0402NF or BT149G.
>>
>> piglet
>
> Yes, that might work - at least as a starting point. Need to poke at the
> values a bit and keep the patent design in mind too - I suspect the
> sensitive gate SCR didn't exist then.
>
> Thanks!
>
> John :-#)#
>

Could use an optocoupler to level-shift the trigger pulse and a
PIC...that's not much fun either, though...

[Bill Martin]

Nah, they are just xenon-phobic :-)

[DecadentLinux...@decadence.org]

bitrex <us...@example.net> wrote in news:hYegI.69395$2A5....@fx45.iad:

> Sounds like you have something to prove.

Your pschologist attitude is not matched by your education. Stay out
of the personal assessment opinion crap.

[bitrex]

Have you given your inner child a hug today, though