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

On 4/21/2021 5:20 PM, Spehro Pefhany wrote:
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.

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. p