Need substitute for old Siliconix FET to replace Thyratron...

[Fred Bloggs]

On Sunday, August 6, 2023 at 2:30:52 PM UTC-4, legg wrote:

On Sun, 6 Aug 2023 08:37:41 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:
On Saturday, August 5, 2023 at 9:07:07?PM UTC-4, John Robertson wrote:
On 2023/08/05 1:29 p.m., legg wrote:
On Thu, 3 Aug 2023 17:26:58 -0700, John Robertson <j...@flippers.com
wrote:



Schematic is here:
https://www.flippers.com/pdfs/2D21_2050_Solid_state_Thyratron.pdf

My goal is to replace the 2D21 Thyratron tube used reading and writing
to core memory for a 1955 jukebox:
https://www.flippers.com/pdfs/2D21_Thyratron_tube.pdf


There may be something seriously wrong with your solidc state sub
pinout.

2D21 pins 7 and 5 are normally connected together, internally.

2D21 pin 3 is a heater terminal, with no cathose or anode contact.
Your solid state drawing seems to anticipate an anode function.

2D21 pins 2 and 7 will normally never see useful low voltage juice for
rectification. I suspect that the sub wants a heater supply on these
terminals. 2D21 isolated heater is on pins 3 and 4.

Recheck it. maybe you\'re numbering from the top view rather than the
bottom.

RL
Actually the schematic drawing is from an old application note (I assume
Siliconix made it) for replacing a 2050 with an SCR and JFET - as the
original title said.

I\'m figuring (hoping) that the 2D21 is close enough in response to the
2050 that the circuit can be used with just putting the 2050 pins to
where the 2D21 is.

All the 2D21 circuits are configured for EC2=0V shied grid to cathode.
That puts you on the 0V parametric on the Average Control Characteristics
datasheet curve, which shows an EC1 trigger voltage of -2V for an anode
voltage of 125V, which is about what they\'re using.

Relative to cathode and within a few PN junction drops, the EC1 external
drive has to be VP + VCR39 to bias Q31 into conduction. If CR39 is a 6.2V,
then for Vp=-15, the circuit will trigger at about -15 + 6.3 = -8.7V applied
to EC1 by external circuit, mainly because gfs is so huge-ish.

CR38, CR40 are there to clamp positive EC1 drives required to trigger
with EC2 biases around -2V or more negative, which is not used AFAICS.

Schematic shows the heater potential pinned at about 30V more positive
than the cathode (R25/R26). This means it is not necessary for Q31 to
have a 150V BVGSS, and you can probably get away with 60V breakdown,
and those are available. Just select one with 20,000 umho or so.

If parts of the circuit still functional, measure those potentials with
high-z meter, especially heater-cathode differential, to verify before
proceeding. the heater-cathode potential is determining the BVGSS
required of the JFET.

Using the isolated heater supply for local DC biasing in a circuit
where the heater supply actually serves multiple tubes could be a
right mess, with a resulting direct connection between sections.

The 2D21 has a maximum rating of heater more positive than cathode of 25V, and heater more negative than cathode of 100V, so it has to made fixed. By connecting heater to -96V like they do, they put the heater at a common mode voltage of -96V, relative to ground, with cathode biased at -125V keeps everything in bounds.

RL

 

[Fred Bloggs]

On Sunday, August 6, 2023 at 2:23:16 PM UTC-4, piglet wrote:

On 06/08/2023 2:18 am, John Robertson wrote:
On 2023/08/05 12:18 p.m., piglet wrote:
On 04/08/2023 7:20 pm, piglet wrote:
On 04/08/2023 1:26 am, John Robertson wrote:
I have a circuit to replace a 2050 Thyratron tube with a FET and an
SCR C106, but I am having trouble sourcing the FET as I am not sure
how to translate the only specs on it that I can find to something
more modern.

It was made by Siliconix # U266 or FN2651.

Specs are as follows:
-------
https://www.flippers.com/pdfs/Siliconix_RAE_1968_Catalog_Redacted.pdf

Igss = 6.0 nA
BVgss = 150V
Vp = 15.0V
Ipss = 100mA (min) to 300mA (max)
Gfs (umho) = 20K (min) to 40K (max)
Rds = 100 Ohms
Id(off) = 1.5nA
-------

Igss looks like Maximum gate current
BVgss is breakdown voltage Gate - Source I assume
What is Vp? Minimum turn on voltage?
Ipss is maximum current of what?
Gfs is inductance it would appear...
Rds is maximum On resistance
Id(off) - is that leakage?

Modern FETs don\'t use all the same descriptors though - at least not
that I\'ve found on digikey and I can\'t find any info on the
U266(FN2651) other than the page out of the RAE distributor\'s catalog

Schematic is here:
https://www.flippers.com/pdfs/2D21_2050_Solid_state_Thyratron.pdf

My goal is to replace the 2D21 Thyratron tube used reading and
writing to core memory for a 1955 jukebox:
https://www.flippers.com/pdfs/2D21_Thyratron_tube.pdf

Thanks!

John :-#)#



Vp is the pinchoff voltage; how negative the gate voltage has to be
for drain-source to be non-conducting - which could be Id(off) or
some other specified \"off\" current.

Gfs is forward transconductance; how drain-source current changes per
change in gate voltage.

Idss is the saturation drain-source current at zero gate volts.

High voltage JFETs are now very hard to get but you should be easily
able to use a modern depletion mosfet like LND150/250

piglet


That schematic you linked depicting the FET+SCR replacement for a
thyratron tube shows the fet drain supply coming from rectified heater
filament 6.3V supply. That is neat as it prevents triggering without
the heater supply and C31 has charged up.

I think they are assuming that 6.3V has either one side or its
center-tap (if present) near cathode 0V ground which means the drain
voltage is going to be well below 20V. Which makes the JFET
requirements look very undemanding, I can\'t see why they specified the
U266 - I reckon you can probably use just about any garden variety
n-channel JFET (2N5458, J113, 2N3819 etc etc)

I haven\'t figured out how shield grid 2 influences the triggering, do
you have a schematic showing how the 2D21 is used in the jukebox?

piglet


G\'day!

Here is a link to the section of the manual covering that:

https://www.flippers.com/pdfs/Seeburg/V200/Seeburg_V200_Pg_5113-5143_B&W.pdf

The schematics for the 2D21s as used is on page 5128.

I drew a nasty sketch layout out the external and internal connections
for the Read-Out and Write-In 2D21s. The \'scope\' sketch is showing the
Detent Sw. pulse at the junction of R14 and R12 AIR.

https://www.flippers.com/pdfs/Seeburg/V200/TSR1-L6_Write-In&Read-Out.pdf

Thanks for your efforts!

John :-#)#
Ok, good to know that grid 2 is nothing to emulate. I can\'t figure out
from the jukebox schematics how the thyratrons are commutated off after
firing. Are they unlatched by disconnect switches in series or are they
fed from unsmoothed HV rails so get zero voltage at 120Hz rate?

2D21 deionizes for Ib<=0.1 Amps in range of 35-75 us. Ib is the anode current. That\'s not so hard to do.

If a low parts count solid state replacement is wanted then I think a
high voltage depletion mosfet makes the job very simple. Otherwise if
using the heater supply to delay operation a few hundred milliseconds
during power up is wanted then any jelly bean jfet could be used. I put
series caps in both heater supply lines in the hope it solves floating
heater supply issues.

Heater is not floating. It was selected to power the SCR trigger circuit because it is a low voltage, low impedance source, and its common mode is easily managed.

My sketches here:

https://www.dropbox.com/scl/fi/b292ch3sl7pbpv7o0si2h/Thyratron_emulator.pdf?rlkey=2gdmf8ph4wi7r2g5eq2incmb2&raw=1

Those circuits don\'t look like a simplification.

piglet

 

[Fred Bloggs]

On Sunday, August 6, 2023 at 3:11:18 PM UTC-4, legg wrote:

On Sat, 5 Aug 2023 17:10:39 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:
On Friday, August 4, 2023 at 8:55:36?AM UTC-4, legg wrote:
On Thu, 3 Aug 2023 17:26:58 -0700, John Robertson <j...@flippers.com
wrote:
I have a circuit to replace a 2050 Thyratron tube with a FET and an SCR
C106, but I am having trouble sourcing the FET as I am not sure how to
translate the only specs on it that I can find to something more modern.

It was made by Siliconix # U266 or FN2651.

Specs are as follows:
-------
https://www.flippers.com/pdfs/Siliconix_RAE_1968_Catalog_Redacted.pdf

Igss = 6.0 nA
BVgss = 150V
Vp = 15.0V
Ipss = 100mA (min) to 300mA (max)
Gfs (umho) = 20K (min) to 40K (max)
Rds = 100 Ohms
Id(off) = 1.5nA
-------

Igss looks like Maximum gate current
BVgss is breakdown voltage Gate - Source I assume
What is Vp? Minimum turn on voltage?
Ipss is maximum current of what?
Gfs is inductance it would appear...
Rds is maximum On resistance
Id(off) - is that leakage?

Modern FETs don\'t use all the same descriptors though - at least not
that I\'ve found on digikey and I can\'t find any info on the U266(FN2651)
other than the page out of the RAE distributor\'s catalog

Schematic is here:
https://www.flippers.com/pdfs/2D21_2050_Solid_state_Thyratron.pdf

My goal is to replace the 2D21 Thyratron tube used reading and writing
to core memory for a 1955 jukebox:
https://www.flippers.com/pdfs/2D21_Thyratron_tube.pdf

Thanks!

John :-#)#
Although it\'s mounted in a stud package and has that
weird gate voltage rating, it\'s only rated at 20Vds

BVgss is breakdown voltage D-S with G-S shorted. Datasheet says 150V. Where are you getting 20V?
Datasheets specify BVDSS and BVGSS but these are \"forward\" breakdown
voltages - ie the absolute maximum Vds before avalanche breakdown of
the drain body pn junction, and the maximum gate drive voltage before
the electric field breaks down the gate oxide.
BVDSS - Drain to source voltage breakdown - third terminal (G) short
to source
BVGSS - Gate to source voltage breakdown - third terminal (D) short to
source.

You can\'t Specify BVDSS of a Jfet, because a shorted gate results in a
conducting device (an impractical test with too much device stress
muddying up the water) - but you can specify BVDS becausae it assumes
non-conductive biasing of the control terminal.

Thanks for the clarification.

For this circuit, BVGSS is what matters, because of the potentially high voltage between heater and cathode. The DC derived from the 6.3VAC isn\'t going to stress a VDS, max of any reasonable FET. In the juke box circuit, heater to cathode is 30V, so any JFET with a BVGSS greater than that will handle it.

RL

 

[Fred Bloggs]

On Sunday, August 6, 2023 at 2:48:29 PM UTC-4, legg wrote:

On Sat, 5 Aug 2023 17:10:39 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:
On Friday, August 4, 2023 at 8:55:36?AM UTC-4, legg wrote:
On Thu, 3 Aug 2023 17:26:58 -0700, John Robertson <j...@flippers.com
wrote:
I have a circuit to replace a 2050 Thyratron tube with a FET and an SCR
C106, but I am having trouble sourcing the FET as I am not sure how to
translate the only specs on it that I can find to something more modern.

It was made by Siliconix # U266 or FN2651.

Specs are as follows:
-------
https://www.flippers.com/pdfs/Siliconix_RAE_1968_Catalog_Redacted.pdf

Igss = 6.0 nA
BVgss = 150V
Vp = 15.0V
Ipss = 100mA (min) to 300mA (max)
Gfs (umho) = 20K (min) to 40K (max)
Rds = 100 Ohms
Id(off) = 1.5nA
-------

Igss looks like Maximum gate current
BVgss is breakdown voltage Gate - Source I assume
What is Vp? Minimum turn on voltage?
Ipss is maximum current of what?
Gfs is inductance it would appear...
Rds is maximum On resistance
Id(off) - is that leakage?

Modern FETs don\'t use all the same descriptors though - at least not
that I\'ve found on digikey and I can\'t find any info on the U266(FN2651)
other than the page out of the RAE distributor\'s catalog

Schematic is here:
https://www.flippers.com/pdfs/2D21_2050_Solid_state_Thyratron.pdf

My goal is to replace the 2D21 Thyratron tube used reading and writing
to core memory for a 1955 jukebox:
https://www.flippers.com/pdfs/2D21_Thyratron_tube.pdf

Thanks!

John :-#)#
Although it\'s mounted in a stud package and has that
weird gate voltage rating, it\'s only rated at 20Vds

BVgss is breakdown voltage D-S with G-S shorted. Datasheet says 150V. Where are you getting 20V?
Datasheets specify BVDSS and BVGSS but these are \"forward\" breakdown
voltages - ie the absolute maximum Vds before avalanche breakdown of
the drain body pn junction, and the maximum gate drive voltage before
the electric field breaks down the gate oxide.

BVDSS - Drain to source voltage breakdown
BVGSS - Gate to source voltage breakdown
Big one is 500-900mA Idss .

U244 similar at 25Vds.

Old soviet surplus part KP903 (2P903) (~ ebay or amazon) might fit.

https://ipelectron.ru/upload/iblock/17f/17f60436ccfccebfbb284f2c7eaa89f3.pdf

I picked up two last year when they were offered by multiple
vendors @ US$5, if that\'s any use to you.

I just checked the 1981 Siliconix Designing with FETs handbook. VDS,max, is a breakdown, but not a PN junction breakdown. It is an avalanche of the channel conduction region. Functionally it means VGS loses control over IDS.

RL

 

[piglet]

On 06/08/2023 23:50, Fred Bloggs wrote:

On Sunday, August 6, 2023 at 2:23:16 PM UTC-4, piglet wrote:
My sketches here:

https://www.dropbox.com/scl/fi/b292ch3sl7pbpv7o0si2h/Thyratron_emulator.pdf?rlkey=2gdmf8ph4wi7r2g5eq2incmb2&raw=1

Those circuits don\'t look like a simplification.


piglet

I think 7 parts (3 res, diode, zener, mosfet, scr) is quite a big
simplification over 15 parts (3 res, 1 cap, 7 diodes, 2 zener, jfet,
scr) of the Davis patent circuit.


But if you want real simple get rid of the scr series diode, all three
resistors, and the zener and it becomes just a mosfet and scr - relies
on idss to limit scr gate current and inbuilt mosfet gate zener. I bet
such an ultra simple circuit will work just fine.

piglet

 

[legg]

On Sun, 6 Aug 2023 15:27:10 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

On Sunday, August 6, 2023 at 2:30:52?PM UTC-4, legg wrote:
On Sun, 6 Aug 2023 08:37:41 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:
On Saturday, August 5, 2023 at 9:07:07?PM UTC-4, John Robertson wrote:
On 2023/08/05 1:29 p.m., legg wrote:
On Thu, 3 Aug 2023 17:26:58 -0700, John Robertson <j...@flippers.com
wrote:



Schematic is here:
https://www.flippers.com/pdfs/2D21_2050_Solid_state_Thyratron.pdf

My goal is to replace the 2D21 Thyratron tube used reading and writing
to core memory for a 1955 jukebox:
https://www.flippers.com/pdfs/2D21_Thyratron_tube.pdf


There may be something seriously wrong with your solidc state sub
pinout.

2D21 pins 7 and 5 are normally connected together, internally.

2D21 pin 3 is a heater terminal, with no cathose or anode contact.
Your solid state drawing seems to anticipate an anode function.

2D21 pins 2 and 7 will normally never see useful low voltage juice for
rectification. I suspect that the sub wants a heater supply on these
terminals. 2D21 isolated heater is on pins 3 and 4.

Recheck it. maybe you\'re numbering from the top view rather than the
bottom.

RL
Actually the schematic drawing is from an old application note (I assume
Siliconix made it) for replacing a 2050 with an SCR and JFET - as the
original title said.

I\'m figuring (hoping) that the 2D21 is close enough in response to the
2050 that the circuit can be used with just putting the 2050 pins to
where the 2D21 is.

All the 2D21 circuits are configured for EC2=0V shied grid to cathode.
That puts you on the 0V parametric on the Average Control Characteristics
datasheet curve, which shows an EC1 trigger voltage of -2V for an anode
voltage of 125V, which is about what they\'re using.

Relative to cathode and within a few PN junction drops, the EC1 external
drive has to be VP + VCR39 to bias Q31 into conduction. If CR39 is a 6.2V,
then for Vp=-15, the circuit will trigger at about -15 + 6.3 = -8.7V applied
to EC1 by external circuit, mainly because gfs is so huge-ish.

CR38, CR40 are there to clamp positive EC1 drives required to trigger
with EC2 biases around -2V or more negative, which is not used AFAICS.

Schematic shows the heater potential pinned at about 30V more positive
than the cathode (R25/R26). This means it is not necessary for Q31 to
have a 150V BVGSS, and you can probably get away with 60V breakdown,
and those are available. Just select one with 20,000 umho or so.

If parts of the circuit still functional, measure those potentials with
high-z meter, especially heater-cathode differential, to verify before
proceeding. the heater-cathode potential is determining the BVGSS
required of the JFET.

Using the isolated heater supply for local DC biasing in a circuit
where the heater supply actually serves multiple tubes could be a
right mess, with a resulting direct connection between sections.

The 2D21 has a maximum rating of heater more positive than cathode of 25V,
and heater more negative than cathode of 100V, so it has to made fixed.
By connecting heater to -96V like they do, they put the heater at a
common mode voltage of -96V, relative to ground, with cathode biased at
-125V keeps everything in bounds.

In the TSR3-L6, using 2050 types, things are fairly simple with V2 and
V6 6V3AC heater lines being grounded on one end and their cathodes
being set also at ground potential. Grid bias is developed
independently at ~ -28V w/r to ground.

The TSR1-L6 using 2D21s isn\'t so straight forward. The 6V1AC heater
line for V2 and V6 is floating and is also used off-schematic (J7).
Cathodes remain grounded and grids are still biased to ~ -28V.
However;
The V7 and V3 parts are cathode biased to a low-power (zener-regulated
) -120V and their grids are biased separately to a similarly low-
power -150V zener. Their 6V3AC heaters are also isolated and exported
off-circuit (J17).
If the circuits will function with these \'cathodes\' shorted together,
then the rectified heater source for the subtitute circuit could work
without much interference.

Perhaps this is a capacitive discharge arrangement, to energize the
solenoids? Could provide quenching, but only on low rep-rates.

RL

 

[legg]

On Mon, 7 Aug 2023 08:29:12 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 06/08/2023 23:50, Fred Bloggs wrote:
On Sunday, August 6, 2023 at 2:23:16?PM UTC-4, piglet wrote:
My sketches here:

https://www.dropbox.com/scl/fi/b292ch3sl7pbpv7o0si2h/Thyratron_emulator.pdf?rlkey=2gdmf8ph4wi7r2g5eq2incmb2&raw=1

Those circuits don\'t look like a simplification.


piglet

I think 7 parts (3 res, diode, zener, mosfet, scr) is quite a big
simplification over 15 parts (3 res, 1 cap, 7 diodes, 2 zener, jfet,
scr) of the Davis patent circuit.


But if you want real simple get rid of the scr series diode, all three
resistors, and the zener and it becomes just a mosfet and scr - relies
on idss to limit scr gate current and inbuilt mosfet gate zener. I bet
such an ultra simple circuit will work just fine.

piglet

I guess you\'d have to be there, to fiddle around.

Complexity will depend on whether it\'s intended to work
everywhere a thyristron is supposed to, or whether it
just has to work in this circuit.

RL

 

[John Robertson]

On 2023/08/07 5:59 a.m., legg wrote:

On Mon, 7 Aug 2023 08:29:12 +0100, piglet <erichpwagner@hotmail.com
wrote:

On 06/08/2023 23:50, Fred Bloggs wrote:
On Sunday, August 6, 2023 at 2:23:16?PM UTC-4, piglet wrote:
My sketches here:

https://www.dropbox.com/scl/fi/b292ch3sl7pbpv7o0si2h/Thyratron_emulator.pdf?rlkey=2gdmf8ph4wi7r2g5eq2incmb2&raw=1

Those circuits don\'t look like a simplification.


piglet

I think 7 parts (3 res, diode, zener, mosfet, scr) is quite a big
simplification over 15 parts (3 res, 1 cap, 7 diodes, 2 zener, jfet,
scr) of the Davis patent circuit.


But if you want real simple get rid of the scr series diode, all three
resistors, and the zener and it becomes just a mosfet and scr - relies
on idss to limit scr gate current and inbuilt mosfet gate zener. I bet
such an ultra simple circuit will work just fine.

piglet

I guess you\'d have to be there, to fiddle around.

Complexity will depend on whether it\'s intended to work
everywhere a thyristron is supposed to, or whether it
just has to work in this circuit.

RL

I primarily want it to work in these three applications used in this
V200 model of Seeburg jukebox: Read-Out, Write-In, and Trip.

Seeburg made a nice little test circuit for the 2D21s as used in their
machine - if the tube works in the Read-Out circuit using the adapter,
then it will work in the other two as well. Read-Out was always the most
critical - reading if those torroids flip state or not. I have a theory
document somewhere on my computer, but can\'t find it because I didn\'t
name it correctly or put into the correct directory - it spoke of how
this new model of jukebox (the articlas of 1955) used the torroids as an
example of magnetic memory storage in the mid-50s...if I find it I will
post a link, it was historically interesting, but not too helpful for
solving this particular problem AIR.

Later someone can take that new circuit and use it to replace most if
not all 2D21s - would be fine by me!

Thanks,

John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John\'s Jukes Ltd.
#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.\"

 

[legg]

On Mon, 7 Aug 2023 10:53:24 -0700, John Robertson <jrr@flippers.com>
wrote:

<snip>

I guess you\'d have to be there, to fiddle around.

Complexity will depend on whether it\'s intended to work
everywhere a thyristron is supposed to, or whether it
just has to work in this circuit.

RL

I primarily want it to work in these three applications used in this
V200 model of Seeburg jukebox: Read-Out, Write-In, and Trip.

Seeburg made a nice little test circuit for the 2D21s as used in their
machine - if the tube works in the Read-Out circuit using the adapter,
then it will work in the other two as well. Read-Out was always the most
critical - reading if those torroids flip state or not. I have a theory
document somewhere on my computer, but can\'t find it because I didn\'t
name it correctly or put into the correct directory - it spoke of how
this new model of jukebox (the articlas of 1955) used the torroids as an
example of magnetic memory storage in the mid-50s...if I find it I will
post a link, it was historically interesting, but not too helpful for
solving this particular problem AIR.

Later someone can take that new circuit and use it to replace most if
not all 2D21s - would be fine by me!

Thanks,

John :-#)#

Have you got a working unit you can use as reference?

RL

 

[legg]

On Mon, 7 Aug 2023 10:53:24 -0700, John Robertson <jrr@flippers.com>
wrote:

Later someone can take that new circuit and use it to replace most if
not all 2D21s - would be fine by me!

Thanks,

John :-#)#

Do you have broken semiconductor replacements that you\'re trying
to repair, or are you anticipating constructing a semi replacement
based on the literature at hand, assuming that they will work?

RL

 

[John Robertson]

On 2023/08/07 3:27 p.m., legg wrote:

On Mon, 7 Aug 2023 10:53:24 -0700, John Robertson <jrr@flippers.com
wrote:

snip

I guess you\'d have to be there, to fiddle around.

Complexity will depend on whether it\'s intended to work
everywhere a thyristron is supposed to, or whether it
just has to work in this circuit.

RL

I primarily want it to work in these three applications used in this
V200 model of Seeburg jukebox: Read-Out, Write-In, and Trip.

Seeburg made a nice little test circuit for the 2D21s as used in their
machine - if the tube works in the Read-Out circuit using the adapter,
then it will work in the other two as well. Read-Out was always the most
critical - reading if those torroids flip state or not. I have a theory
document somewhere on my computer, but can\'t find it because I didn\'t
name it correctly or put into the correct directory - it spoke of how
this new model of jukebox (the articlas of 1955) used the torroids as an
example of magnetic memory storage in the mid-50s...if I find it I will
post a link, it was historically interesting, but not too helpful for
solving this particular problem AIR.

Later someone can take that new circuit and use it to replace most if
not all 2D21s - would be fine by me!

Thanks,

John :-#)#

Have you got a working unit you can use as reference?

RL

I have a working jukebox with a working 2D21 for testing.

I just want to fix this PERMANENTLY! At least, as permanent as solid
state items are when run well within their limits that is... Many
jukeboxes had trouble with this version of control centre, and my hope
is to make a simple replacement part for the 2D21 that can simply be
plugged into the tube\'s socket.

John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John\'s Jukes Ltd.
#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.\"

 

[legg]

On Mon, 7 Aug 2023 21:31:48 -0700, John Robertson <jrr@flippers.com>
wrote:

On 2023/08/07 3:27 p.m., legg wrote:
On Mon, 7 Aug 2023 10:53:24 -0700, John Robertson <jrr@flippers.com
wrote:

snip

I guess you\'d have to be there, to fiddle around.

Complexity will depend on whether it\'s intended to work
everywhere a thyristron is supposed to, or whether it
just has to work in this circuit.

RL

I primarily want it to work in these three applications used in this
V200 model of Seeburg jukebox: Read-Out, Write-In, and Trip.

Seeburg made a nice little test circuit for the 2D21s as used in their
machine - if the tube works in the Read-Out circuit using the adapter,
then it will work in the other two as well. Read-Out was always the most
critical - reading if those torroids flip state or not. I have a theory
document somewhere on my computer, but can\'t find it because I didn\'t
name it correctly or put into the correct directory - it spoke of how
this new model of jukebox (the articlas of 1955) used the torroids as an
example of magnetic memory storage in the mid-50s...if I find it I will
post a link, it was historically interesting, but not too helpful for
solving this particular problem AIR.

Later someone can take that new circuit and use it to replace most if
not all 2D21s - would be fine by me!

Thanks,

John :-#)#

Have you got a working unit you can use as reference?

RL

I have a working jukebox with a working 2D21 for testing.

I just want to fix this PERMANENTLY! At least, as permanent as solid
state items are when run well within their limits that is... Many
jukeboxes had trouble with this version of control centre, and my hope
is to make a simple replacement part for the 2D21 that can simply be
plugged into the tube\'s socket.

John :-#)#

You have \'one\' working 2D21 that you\'re swapping around to check
individual local cct function in a TSR?

What is the selector reciever type number that ~ functions? There
are two types in the Seeburg manual. One uses 4x 2D21 - the other
uses 2x 2050.

Have you got 7-pin bases to build 2D21 substitutes onto? What\'s the
PN and supplier?

The problem isn\'t to make the circuit go, so much as to duplicate
the innards of the thyratron package. The patent drawings depend
on independent heater power to develop \'sky-hook\' voltages
internally for the substitute cct.

I missed the the -96V bias on the V1, V3 and V7 6V3AC heaters in
TSR1-L6. These are the tubes running cathodes at ~ -150VDC.

TSR J5 carriee 150VAC to \'mechanism. Where does this link up
in the manual.

You DO know that you can still buy these things, new from
distribution? (from Newark FGS )

https://www.newark.com/richardson-electronics/2d21/electron-tube/dp/05F9500
http://www.electrontubestore.com/index.php?main_page=product_info&products_id=424

Not cheap, admittedly, but usefull to make sure that everything
else is functional, before diving off the deep end, or starting a
science project. The latter would definitely end up costing
somebody more than a few weekends of fussing around.

RL

 

[John Robertson]

On 2023/08/08 8:39 a.m., legg wrote:

On Mon, 7 Aug 2023 21:31:48 -0700, John Robertson <jrr@flippers.com
wrote:

On 2023/08/07 3:27 p.m., legg wrote:
On Mon, 7 Aug 2023 10:53:24 -0700, John Robertson <jrr@flippers.com
wrote:

snip

I guess you\'d have to be there, to fiddle around.

Complexity will depend on whether it\'s intended to work
everywhere a thyristron is supposed to, or whether it
just has to work in this circuit.

RL

I primarily want it to work in these three applications used in this
V200 model of Seeburg jukebox: Read-Out, Write-In, and Trip.

Seeburg made a nice little test circuit for the 2D21s as used in their
machine - if the tube works in the Read-Out circuit using the adapter,
then it will work in the other two as well. Read-Out was always the most
critical - reading if those torroids flip state or not. I have a theory
document somewhere on my computer, but can\'t find it because I didn\'t
name it correctly or put into the correct directory - it spoke of how
this new model of jukebox (the articlas of 1955) used the torroids as an
example of magnetic memory storage in the mid-50s...if I find it I will
post a link, it was historically interesting, but not too helpful for
solving this particular problem AIR.

Later someone can take that new circuit and use it to replace most if
not all 2D21s - would be fine by me!

Thanks,

John :-#)#

Have you got a working unit you can use as reference?

RL

I have a working jukebox with a working 2D21 for testing.

I just want to fix this PERMANENTLY! At least, as permanent as solid
state items are when run well within their limits that is... Many
jukeboxes had trouble with this version of control centre, and my hope
is to make a simple replacement part for the 2D21 that can simply be
plugged into the tube\'s socket.

John :-#)#

You have \'one\' working 2D21 that you\'re swapping around to check
individual local cct function in a TSR?

Yes, and a bunch of \"new\" 2D21s that are too fussy.

What is the selector reciever type number that ~ functions? There
are two types in the Seeburg manual. One uses 4x 2D21 - the other
uses 2x 2050.

I\'m using the 2D21 version TSR1-L6

Have you got 7-pin bases to build 2D21 substitutes onto? What\'s the
PN and supplier?

Yes, I found them on eBay, they should work.

The problem isn\'t to make the circuit go, so much as to duplicate
the innards of the thyratron package. The patent drawings depend
on independent heater power to develop \'sky-hook\' voltages
internally for the substitute cct.

I missed the the -96V bias on the V1, V3 and V7 6V3AC heaters in
TSR1-L6. These are the tubes running cathodes at ~ -150VDC.

TSR J5 carriee 150VAC to \'mechanism. Where does this link up
in the manual.

From the 0A2 which is the regulator tube on the 6X4 negative supply.

You DO know that you can still buy these things, new from
distribution? (from Newark FGS )

https://www.newark.com/richardson-electronics/2d21/electron-tube/dp/05F9500
http://www.electrontubestore.com/index.php?main_page=product_info&products_id=424

I\'ve bought new 2D21s from Newark, and they don\'t always work in the
machine.

Not cheap, admittedly, but usefull to make sure that everything
else is functional, before diving off the deep end, or starting a
science project. The latter would definitely end up costing
somebody more than a few weekends of fussing around.

RL

It is possible the machine I have has a problem with the TSR1-L6, but
I\'ve rebuilt it, verified the voltages, new resistors, caps, scoped it,
poked and prodded, and there is only one 2D21 that works just fine in
the Read-Out circuit out of perhaps ten I have that were NOS - five from
Newark.

I made a simple solid-state 2D21 that operates the Trip function
properly, but won\'t work in the Read-Out. The Read-Out spikes from the
Detent Switch are not getting close enough to Zero volts to trip most of
the tubes. The spikes look perfect at the Detent Switch and at the
junction of C11 and R12.

Unfortunately I do not have another TSR1-L6 to compare this one too, I
suspect I may be overlooking something really obvious...

John :-#(#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John\'s Jukes Ltd.
#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.\"

 

[legg]

On Tue, 8 Aug 2023 09:51:52 -0700, John Robertson <jrr@flippers.com>
wrote:

You have \'one\' working 2D21 that you\'re swapping around to check
individual local cct function in a TSR?

Yes, and a bunch of \"new\" 2D21s that are too fussy.


What is the selector reciever type number that ~ functions? There
are two types in the Seeburg manual. One uses 4x 2D21 - the other
uses 2x 2050.

I\'m using the 2D21 version TSR1-L6

Have you got 7-pin bases to build 2D21 substitutes onto? What\'s the
PN and supplier?

Yes, I found them on eBay, they should work.


The problem isn\'t to make the circuit go, so much as to duplicate
the innards of the thyratron package. The patent drawings depend
on independent heater power to develop \'sky-hook\' voltages
internally for the substitute cct.

I missed the the -96V bias on the V1, V3 and V7 6V3AC heaters in
TSR1-L6. These are the tubes running cathodes at ~ -150VDC.

TSR J5 carriee 150VAC to \'mechanism. Where does this link up
in the manual.

From the 0A2 which is the regulator tube on the 6X4 negative supply.

You DO know that you can still buy these things, new from
distribution? (from Newark FGS )

https://www.newark.com/richardson-electronics/2d21/electron-tube/dp/05F9500
http://www.electrontubestore.com/index.php?main_page=product_info&products_id=424

I\'ve bought new 2D21s from Newark, and they don\'t always work in the
machine.


Not cheap, admittedly, but usefull to make sure that everything
else is functional, before diving off the deep end, or starting a
science project. The latter would definitely end up costing
somebody more than a few weekends of fussing around.

RL


It is possible the machine I have has a problem with the TSR1-L6, but
I\'ve rebuilt it, verified the voltages, new resistors, caps, scoped it,
poked and prodded, and there is only one 2D21 that works just fine in
the Read-Out circuit out of perhaps ten I have that were NOS - five from
Newark.

I made a simple solid-state 2D21 that operates the Trip function
properly, but won\'t work in the Read-Out. The Read-Out spikes from the
Detent Switch are not getting close enough to Zero volts to trip most of
the tubes. The spikes look perfect at the Detent Switch and at the
junction of C11 and R12.

Read-out spikes from the detent switch (from J6 pin5, supposedly aimed
to fire V3 read-out thyratron) are applied through C11/R11 to a node
(C11/R12) that is biased at -150VDC.

To fire the thyratron, this C11/R12 node voltage has to approach the
-118VDC cathode voltage stored on C13 (0.1uF). If the detent switch
produces a grounded pulse (150V positive-going impulse), there should
DOUBLE sufficient signal still left after filtering at the junction
of R12/R13, based on modelling.

If C13 hasn\'t charged \'up\' to -118V, the read-out pulse going into
J5 pin5 may be ineffective, but its recharge time is less than 20ms.
Recharging the pulse forming input network from the detent switch is
longer ~40ms.

Leakage paths for C13 include C1 on J2 pin7 and anything in the
\'Service Switch\', if J2 is connected. Anything loading J6 pin5 will
reduce the amplitude of the detent pulse - it\'s impedance is very
high (at 2M7).

Simulations suggest that with componts currently employed in
grid drive and timing, very simple mosfet-buffered SCRs will
function in the floating cathode circuit, even with simple back-
to-back zeners protecting the gate and a 1K gate-cathode resistor
on the scr. There is a delay while the mosfet gate charges, but
that\'s all. No skyhook voltage or heater power required.

(LTcad built-in models for BSC320N20NS3, S4025L, and 1N4746 were used)

Function of V7 Write-In is practically the same.

RL

 

[legg]

On Tue, 8 Aug 2023 09:51:52 -0700, John Robertson <jrr@flippers.com>
wrote:

Sims also suggested that anode loads above 220R seriously affected
discharge timing, probably due to high scr \'hold\' current.
The fet-scr \'darlington\' would discharge the 100n cap effectively
over a wide range of gate input resistor (1k-100K), if the original
input pulse was clean.

RL

 

[John Robertson]

On 2023/08/08 8:34 p.m., legg wrote:

On Tue, 8 Aug 2023 09:51:52 -0700, John Robertson <jrr@flippers.com
wrote:

You have \'one\' working 2D21 that you\'re swapping around to check
individual local cct function in a TSR?

Yes, and a bunch of \"new\" 2D21s that are too fussy.


What is the selector reciever type number that ~ functions? There
are two types in the Seeburg manual. One uses 4x 2D21 - the other
uses 2x 2050.

I\'m using the 2D21 version TSR1-L6

Have you got 7-pin bases to build 2D21 substitutes onto? What\'s the
PN and supplier?

Yes, I found them on eBay, they should work.


The problem isn\'t to make the circuit go, so much as to duplicate
the innards of the thyratron package. The patent drawings depend
on independent heater power to develop \'sky-hook\' voltages
internally for the substitute cct.

I missed the the -96V bias on the V1, V3 and V7 6V3AC heaters in
TSR1-L6. These are the tubes running cathodes at ~ -150VDC.

TSR J5 carriee 150VAC to \'mechanism. Where does this link up
in the manual.

From the 0A2 which is the regulator tube on the 6X4 negative supply.

You DO know that you can still buy these things, new from
distribution? (from Newark FGS )

https://www.newark.com/richardson-electronics/2d21/electron-tube/dp/05F9500
http://www.electrontubestore.com/index.php?main_page=product_info&products_id=424

I\'ve bought new 2D21s from Newark, and they don\'t always work in the
machine.


Not cheap, admittedly, but usefull to make sure that everything
else is functional, before diving off the deep end, or starting a
science project. The latter would definitely end up costing
somebody more than a few weekends of fussing around.

RL


It is possible the machine I have has a problem with the TSR1-L6, but
I\'ve rebuilt it, verified the voltages, new resistors, caps, scoped it,
poked and prodded, and there is only one 2D21 that works just fine in
the Read-Out circuit out of perhaps ten I have that were NOS - five from
Newark.

I made a simple solid-state 2D21 that operates the Trip function
properly, but won\'t work in the Read-Out. The Read-Out spikes from the
Detent Switch are not getting close enough to Zero volts to trip most of
the tubes. The spikes look perfect at the Detent Switch and at the
junction of C11 and R12.

Read-out spikes from the detent switch (from J6 pin5, supposedly aimed
to fire V3 read-out thyratron) are applied through C11/R11 to a node
(C11/R12) that is biased at -150VDC.

To fire the thyratron, this C11/R12 node voltage has to approach the
-118VDC cathode voltage stored on C13 (0.1uF). If the detent switch
produces a grounded pulse (150V positive-going impulse), there should
DOUBLE sufficient signal still left after filtering at the junction
of R12/R13, based on modelling.

If C13 hasn\'t charged \'up\' to -118V, the read-out pulse going into
J5 pin5 may be ineffective, but its recharge time is less than 20ms.
Recharging the pulse forming input network from the detent switch is
longer ~40ms.

Leakage paths for C13 include C1 on J2 pin7 and anything in the
\'Service Switch\', if J2 is connected. Anything loading J6 pin5 will
reduce the amplitude of the detent pulse - it\'s impedance is very
high (at 2M7).

Simulations suggest that with componts currently employed in
grid drive and timing, very simple mosfet-buffered SCRs will
function in the floating cathode circuit, even with simple back-
to-back zeners protecting the gate and a 1K gate-cathode resistor
on the scr. There is a delay while the mosfet gate charges, but
that\'s all. No skyhook voltage or heater power required.

(LTcad built-in models for BSC320N20NS3, S4025L, and 1N4746 were used)

Function of V7 Write-In is practically the same.

RL

Well, thanks for the lesson on the operation of the circuit! I must
confess that I never understood it as well as you have figured out with
the little information that I have provided.

Much appreciated!

May I ask how (or what program used) you are simulating the operation?
If this is an inexpensive simulator I\'d consider getting it so I can
poke in values to see what I would get...

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John\'s Jukes Ltd.
#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.\"

 

[legg]

On Tue, 8 Aug 2023 22:27:35 -0700, John Robertson <jrr@flippers.com>
wrote:

<snip>

May I ask how (or what program used) you are simulating the operation?
If this is an inexpensive simulator I\'d consider getting it so I can
poke in values to see what I would get...

John :-#)#

LTspice is free from (now) Analog Devices.

https://www.analog.com/en/design-center/design-tools-and-calculators/ltspice-simulator.html

RL

 

[legg]

On Tue, 8 Aug 2023 22:27:35 -0700, John Robertson <jrr@flippers.com>
wrote:

http://ve3ute.ca/query/read-out_input_amplitude_2_gate_stress_recharge_40m.zip

RL

 

[John Robertson]

On 2023/08/09 10:23 a.m., legg wrote:

On Tue, 8 Aug 2023 22:27:35 -0700, John Robertson <jrr@flippers.com
wrote:

http://ve3ute.ca/query/read-out_input_amplitude_2_gate_stress_recharge_40m.zip

RL

404 - not found...

I was busy the last week and went to look just now.

John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John\'s Jukes Ltd.
#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.\"

 

[legg]

On Sat, 12 Aug 2023 15:05:02 -0700, John Robertson <jrr@flippers.com>
wrote:

On 2023/08/09 10:23 a.m., legg wrote:
On Tue, 8 Aug 2023 22:27:35 -0700, John Robertson <jrr@flippers.com
wrote:

http://ve3ute.ca/query/read-out_input_amplitude_2_gate_stress_recharge_40m.zip

RL

404 - not found...

I was busy the last week and went to look just now.

John :-#)#

Try again.

The posted link was ok, but the target had a \'space\' character
mistakenly inserted - and present in my \'checking\' links.

I didn\'t think that a space character could function in an html
link,so wasn\'t looking - appeared as a line wrap on this reader.

RL