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