Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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

On 2021/04/22 6:35 a.m., bitrex wrote:
On 4/22/2021 4:04 AM, wrote:
bitrex wrote in
:

On 4/21/2021 11:29 PM,

wrote:
bitrex wrote in
:

On 4/21/2021 10:42 PM, Fox's Mercantile wrote:
On 4/21/21 8:31 PM,

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"


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


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


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


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.


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

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."

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

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 :-#)#

--
(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."
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Default A solid state replacement for the lowly 2D21 Thyratrontube...(sorry for the On-Topic post!)

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

On 4/21/21 11:43 PM, bitrex wrote:
On 4/22/2021 1:07 AM, bitrex wrote:
On 4/21/2021 3:47 PM, John Robertson wrote:
On 2021/04/21 11:19 a.m., bitrex wrote:
On 4/21/2021 2:14 PM, John Larkin wrote:
On Wed, 21 Apr 2021 10:28:02 -0700, 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 he

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.


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.

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

John :-#)#


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


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

Nah, they are just xenon-phobic :-)

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

bitrex wrote in :

Sounds like you have something to prove.


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


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

On 4/22/2021 9:09 PM, wrote:
bitrex wrote in :

Sounds like you have something to prove.


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


Have you given your inner child a hug today, though
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