View Single Post
  #29   Report Post  
Posted to,
bitrex bitrex is offline
external usenet poster
Posts: 89
Default A solid state replacement for the lowly 2D21 Thyratrontube...(sorry for the On-Topic post!)

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

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
on machines that passed through my shop...

I should point out that Seeburg only used these 2D21s (three 2D21s
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
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:

Another says it's xenon:

Maybe a mixture of stuff.