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.