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

On Wed, 21 Apr 2021 12:44:37 -0700, John Robertson

On 2021/04/21 11:14 a.m., John Larkin wrote:
On Wed, 21 Apr 2021 10:28:02 -0700, 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 he

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.

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

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

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.

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