Nixie Pinball Display - Schematic feedback

[Zitt]

You guys are more knowledgeable on NIXIE displays; so I'm interested feedback on the schematics and if you see any obvious design errors.

I can’t claim originality here... as I remember the XENON pinball machine at a past TPF which had NIXIE tubes instead of the standard VFD displays. I always thought they were cool.

 

Now that I’m designing Star Trek: The Mirror Universe; I’m thinking that I want to put NIXIE displays in the machine instead of stock Bally displays.

 

I’ve been doing some design work; and have come up with the following schematics which use the IN-12A tubes from Russia. They are nearly the same digit height as a stock display and and are relatively inexpensive compared to other tubes.

Just put the finishing touches on the silk screen for the Base board for the Nixie display.

 

Here’s a image of the boards as they stand today.

Base Board: 

Display Board: 

 

New features added:

1) The “Right angle” Display board has surface mount LEDs under the tubes; the idea here is that when the display is “active” meaning PlayerX is up... the switched LAMP driver on the side of the display turns on these LEDs causing them to backlight the display ... to help identify which player is active. A Brightness POT on the baseboard controls the brightness.

Opto-Isolated the “lamp” input from +5V logic.

 

2) I added decode logic to support 7digit display ROM hacks:

Update 6 Digit Bally pinballs to 7 digit

where buy D5 =1= D6 causes the 7th digit to become active. U3 & U4 provide this functionality.

Feature is jumper selectable to for native 7digit or Rom-Hack 7digit mode via JP1.

 

3) Clearly labeled Test Points with voltages. Added 80V test point.

 

4) Additional decoupling caps near U1,U2,U3 and well as a bulk cap for 5V. 

 

5) Nixie tube display board is at a “right angle” to the base board (like original); but is back set far enough so “front” of IN-12A displays are near same position as the VFD display.

 

6) HV areas “inside” dotted lines. Generous ground planes to help with thermals.

 

7) Same PCB sizes as original.

 

The Schematics are posted here for review... I’ve never designed a display before... so will probably need to do some design tweaks once I get the Tubes in.

http://www.Pinball-Mods.com/blogs/wp-content/uploads/2013/01/Bally7Nixie.pdf

At this time; the design remains my copy-protected property! Once I've proven the design; I'll consider open-sourcing the design for others to build.

 

I went 7digits instead of 6... so they can be used in other machines. I’ll either de-pop NIXIE_A7 or figure out how to make my Bally FW run a 7digit display.

[Quixotic Nixotic]

[Sebastian Götte]

On 02/07/2013 08:02 AM, Zitt wrote:
> 1) The �Right angle� Display board has surface mount LEDs under the
> tubes; the idea here is that when the display is �active� meaning

> PlayerX is up... the switched LAMP driver on the side of the display
> turns on these LEDs causing them to backlight the display ... to help
> identify which player is active. A Brightness POT on the baseboard
> controls the brightness.

> Opto-Isolated the �lamp� input from +5V logic.
You could maybe regulate the nixie current (instead of using LEDs) so
the active display is brighter than the inactive one.

[michael gregg]

Zitt, that sounds like a fun project.

I have only looked at your schematic for a few minutes, so I may not
completely know what is going on.

The first this I see that I do not understand is here I see the opto
isolator. As I understand it, you are planning on running the leds
through it.

The construction of your circuit is a bit confusing to me. It looks
like you are running the base rail of the transistors for your led's
off of a line going through the first led(Q7A)? I'm not sure why you
are doing that. Are you trying to use the led as a current regulator
or something?

It's a good idea to put a limiting resistor on the anodes of your
Nixie tubes to avoid burning them out if you accidentally turn
multiple legs on.

I do not know what your incoming data is like, so I cannot speak very
much to the rest of your circuit. It looks like you get the display
data in on a 4 bit BCD shift register?

What is the section of the circuit with the 4555d and 4503d components doing?

I hope you'll post images of your finished product when you are done. :)

Michael-

[Zitt]

> You could maybe regulate the nixie current (instead of using LEDs) so
> the active display is brighter than the inactive one.

 

Hadn't considered. Truth be told; I saw the LED back lit clocks and basically thought it was a cool idea.

Maybe I'll do that on Rev2.

On Thursday, February 7, 2013 4:25:09 AM UTC-6, mikegregg wrote:

 

<<The first this I see that I do not understand is here I see the opto
isolator.  As I understand it, you are planning on running the leds
through it.

The construction of your circuit is a bit confusing to me. It looks
like you are running the base rail of the transistors for your led's
off of a line going through the first led(Q7A)? I'm not sure why you
are doing that. Are you trying to use the led as a current regulator
or something? >>

 

Q7A is a diode connected Transistor; which is the left half of a standard Current Mirror.

The LED (D7A) and the .7V diode connected transistor are driven by R62 as a current limitor.

Q22 provides a propotional voltage drop against the setting of the Pot at R65. The idea here is that R65 controls the brightness of that single LED (D7A); which is "current mirrored" into the other LEDs. So; controlling one LEDs brightness is "mirrored" into the others.

Q7B-Q1B are all the other side of a current mirror.

http://www.allaboutcircuits.com/vol_3/chpt_4/14.html

<<It's a good idea to put a limiting resistor on the anodes of your
Nixie tubes to avoid burning them out if you accidentally turn
multiple legs on.>> 

 

Already present. 12.5K ... ie R13. 

<<I do not know what your incoming data is like, so I cannot speak very
much to the rest of your circuit. It looks like you get the display
data in on a 4 bit BCD shift register? >>

 

Correct; BCD for the digit. And D7-D1 controlls which "anode" is updated.

<<What is the section of the circuit  with the 4555d and 4503d components doing? >>

 

Address translation for 7digit displays in a 6digit system. Item#2 above:

http://www.pinball4you.ch/okaegi/pro_d7.html

<<I hope you'll post images of your finished product when you are done. :) >>

 

Certainly. :D

John

[michael gregg]

On Thu, Feb 7, 2013 at 9:09 AM, Zitt <zitt...@gmail.com> wrote:
>> You could maybe regulate the nixie current (instead of using LEDs) so
>> the active display is brighter than the inactive one.
>
> Hadn't considered. Truth be told; I saw the LED back lit clocks and
> basically thought it was a cool idea.
> Maybe I'll do that on Rev2.

It would be worth a try to try it out, but I suspect that the
back-lighting will look nicer.

>
> On Thursday, February 7, 2013 4:25:09 AM UTC-6, mikegregg wrote:
>
> <<The first this I see that I do not understand is here I see the opto
> isolator. As I understand it, you are planning on running the leds
> through it.
>
> The construction of your circuit is a bit confusing to me. It looks
> like you are running the base rail of the transistors for your led's
> off of a line going through the first led(Q7A)? I'm not sure why you
> are doing that. Are you trying to use the led as a current regulator
> or something? >>
>
> Q7A is a diode connected Transistor; which is the left half of a standard
> Current Mirror.
> The LED (D7A) and the .7V diode connected transistor are driven by R62 as a
> current limitor.
> Q22 provides a propotional voltage drop against the setting of the Pot at
> R65. The idea here is that R65 controls the brightness of that single LED
> (D7A); which is "current mirrored" into the other LEDs. So; controlling one
> LEDs brightness is "mirrored" into the others.
> Q7B-Q1B are all the other side of a current mirror.
> http://www.allaboutcircuits.com/vol_3/chpt_4/14.html

I see. Thank you for the explination.

>
> <<It's a good idea to put a limiting resistor on the anodes of your
> Nixie tubes to avoid burning them out if you accidentally turn
> multiple legs on.>>
>
> Already present. 12.5K ... ie R13.
>
>
> <<I do not know what your incoming data is like, so I cannot speak very
> much to the rest of your circuit. It looks like you get the display
> data in on a 4 bit BCD shift register? >>
>
> Correct; BCD for the digit. And D7-D1 controlls which "anode" is updated.
>
>
> <<What is the section of the circuit with the 4555d and 4503d components
> doing? >>
>
> Address translation for 7digit displays in a 6digit system. Item#2 above:
> http://www.pinball4you.ch/okaegi/pro_d7.html

Ohh, that makes sense. That explains all of

>
> <<I hope you'll post images of your finished product when you are done. :)
>>>
>
> Certainly. :D
>
> John
>

> --
> You received this message because you are subscribed to the Google Groups
> "neonixie-l" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to neonixie-l+...@googlegroups.com.
> To post to this group, send an email to neoni...@googlegroups.com.
> To view this discussion on the web, visit
> https://groups.google.com/d/msg/neonixie-l/-/9jNsnhOb8eMJ.
>
> For more options, visit https://groups.google.com/groups/opt_out.
>
>

[MrNixie (UK)]

[MrNixie (UK)]

Hello Zitt, first of all, this sounds like an interesting and worthwhile application for nixie tubes! You are to be congratulated on that. I am not saying your design wont work, but you've asked for comments, so here are mine...

I do feel that you may have over complicated the LED drivers a little bit. Seems like an awful lot of semiconductors in there!. First of all, consider wiring pairs of LEDs in series, or even quads in series, depending on what (12V?) power supplies you have to hand. Then current limit them through a series resistor, and wire multiple strings of this arrangement in parallel and then back to just the one switching transistor.

The resistors R56/R57 in your anode drivers are probably a bit low - you've got the best part of 2mA of (expensive) HT flowing down there. The driver transistor q21 etc. won't need that much base drive. I've used values three times yours before, without any issue or ghosting, etc.

You are multiplexing this display on a "one of six" basis. That means each nixie tube is only going to see juice for maybe 15% of the time. Even if you overdrive them, they will be on the dimmer end of their possible light output, and I would imagine that for your application  nice, bright displays are somethiung of a prerequisite. You might want to consider designing the mux to be two sets of "one of three".  As I say, it will work as you've got it, but you may be disappointed in the results.

Check the pin-outs of the nixie tubes - i think you can save maybe one or two pins (you still need the PCB holes, of course, but now electrical connection to some pins).

I think 190V HT may be a bit too "hot". You may find the displays will work fine at 180V, even 170V. The tube's actual striking voltage is probably around 150V. You will need to set the anode current limiting resistors to suit, of course.

That's the thing about electronics, isn't it? there are often many ways of doing it!

Keep us up to date with your progress

[John Rehwinkel]

> You are multiplexing this display on a "one of six" basis. That means each nixie tube is only going to see juice for maybe 15% of the time. Even if you overdrive them, they will be on the dimmer end of their possible light output, and I would imagine that for your application nice, bright displays are somethiung of a prerequisite. You might want to consider designing the mux to be two sets of "one of three".

Unfortunately, this is what the pinball machine provides to the display - BCD code for the current digit, and six (or seven) digit select lines. Getting around this
would require a great deal more in the way of semiconductors.

Interestingly, I was thinking of doing the same mod to my Xenon.

- John

[Quixotic Nixotic]

I had a Xenon at one time. Suzanne Ciani having a synthesised orgasm when you hit the bumpers was great fun. You can see and hear how she did it at:
http://youtu.be/5_dZqjlM430.

Zitt is wrong in saying Xenon had nixies instead of the usual VDF displays. Bally never used VFDs (but Gottlieb did). Xenon never had any nixie tubes either, nor did any US production pinball machine. The French Rally Plays are the only nixie tubed pinball machines. Maybe Zitt remembered a mod someone else had already done?

Xenon used the same flat style of planar neon displays all Ballys had, from the prototype Bow and Arrow in 1974 until they sold out to Midway, a subsidiary of Williams, in 1991, Blackwater being the last Bally.

I'll get my anorak,

John S

[Quixotic Nixotic]

Rally Play games with nixies...

First off was Rally Girl in 1966.

Then West Club in 1967.

Playboy, also 1967.

Comics and Shuss came out in 1968.

Flower's child (sic) is the last and rarest machine. Perhaps only one survives. With that artwork, probably a blessing.

The company folded after the owner's gay relationship broke up. His ex life and business partner took the remainder of the unfinished machines and spares stock and this was traced by pinball historian Gary Flower to a warehouse somewhere in northern Italy, where it had been sold on to someone else. Alas the trail went cold but we hope that this treasure trove might still come to light at some future point, who knows?

The remaining UK spares were all bought from Deith Leisure by Gary Flower himself, who restored and sold on any and all the machines he could find, to private collectors. Gary has none now, although he did source one as a present for pinball designer John Popadiuk in recent years. I don't know how or why, but Gary ended up as gooseberry on John Popadiuk's honeymoon. Gary doesn't swim, but somehow found himself behind John on a jet ski, clinging on for dear life. John had to explain to his new wife that night how he got that set of claw marks down his back.

John S

[kay486]

I absolutely love that video you linked! Thanks.

[Zitt]

On Friday, February 8, 2013 7:22:47 AM UTC-6, jrehwin wrote:

> You are multiplexing this display on a "one of six" basis. That means each nixie tube is only going to see juice for maybe 15% of the time. Even if you overdrive them, they will be on the dimmer end of their possible light output, and I would imagine that for your application  nice, bright displays are somethiung of a prerequisite. You might want to consider designing the mux to be two sets of "one of three".

Unfortunately, this is what the pinball machine provides to the display - BCD code for the current digit, and six (or seven) digit select lines.  Getting around this
would require a great deal more in the way of semiconductors.

 

MrNixie - John is correct. The "one of seven" drive is the requirement of the pinball machine design. These displays are intended to be "drop in replacments"

I'm thinking in "practice" It might be safe to latch the anode address at the same time the bcd digit is latched so that the displays can be on longer. But this is a Rev2 or Rev3 design if I ever get to it.

 

<<I do feel that you may have over complicated the LED drivers a little bit. Seems like an awful lot of semiconductors in there!. First of all, consider wiring pairs of LEDs in series, or even quads in series, depending on what (12V?) power supplies you have to hand. Then current limit them through a series resistor, and wire multiple strings of this arrangement in parallel and then back to just the one switching transistor.>>

 

No 12VDC supplies are brought to the displays. We only have 5VDC and 190VDC comming in. I don't want to put the LEDs on the 190V display because it is a realitvely small current supply (or will be on my machine.) I don't want a boost converter to bring 5V to 12V either. I think for this application; the existing implemenation is proably the best.

<<The resistors R56/R57 in your anode drivers are probably a bit low - you've got the best part of 2mA of (expensive) HT flowing down there. The driver transistor q21 etc. won't need that much base drive. I've used values three times yours before, without any issue or ghosting, etc. >>

Yeah; I wasn't sure about the 12.5K Anode resistors. They calculate fine; but agreed that 12.5K seems low. For my initial proto; I have a 50k pot attached to A1... so I can vary the resistance til I get a reasonable display. My calc was roughtly:

190V-170V-(2*0.3) / 2mA ~= 12.5k

<<I think 190V HT may be a bit too "hot". You may find the displays will work fine at 180V, even 170V. The tube's actual striking voltage is probably around 150V. You will need to set the anode current limiting resistors to suit, of course.>>

Again; limited by "drop in" design to existing display. 190VDC is the incomming PSU rail for a normal display. It's 190+-5Vdc.

<<Zitt is wrong in saying Xenon had nixies instead of the usual VDF displays. Bally never used VFDs (but Gottlieb did). Xenon never had any nixie tubes either, nor did any US production pinball machine. The French Rally Plays are the only nixie tubed pinball machines. Maybe Zitt remembered a mod someone else had already done? >>

 

Correct; I wasn't clear. AFIAK no volume pinball machine used Nixie displays. The XENON I saw; was a modded XENON at TPF. Not stock.

[MrNixie (UK)]

Yes, I kinda missed the point that you were building a "drop-in" module and would thus be limited to the signals and supplies at the connectors. Well, knock one up, and see how it goes!

[Zitt]

PCBs were ordered via batchpcb yesterday. so Now I play the waitin for PCB game.

[Zitt]

(clickable links and embedded pictures at:

http://forums.arcade-museum.com/showpost.php?p=2391595&postcount=43)

The Mirror project was put on hold for the last three weeks... First due to the SxSw Intel LANfest I was hosting... and then Texas Pinball Festival this past weekend. Now that I had the Pins back in the Garage'cade; I've refocused my effort on the Nixie Pinball Display.

I hand assembled the base and display boards and soldered them together. 

I didn't want to commit the untested display to my Bally Star Trek... so I needed to figure out how to facilitate debug.

First problem was how to supply 190VDC to the HV section. Some googling found me some 555 timer circuits which would run off of a 9V. 

Had most of the parts except a 250V 4.7uf cap and a pot. A trip to Frys solved that problem.

A bread board and an ATX power supply and I had a 190V psu. The ATX supply provides +5v to the display and +12V to the 190V psu's input.

Here’s a picture of the prototype 555 190V Nixie supply:

http://www.flickr.com/photos/52968060@N00/8582243194/sizes/l/in/photostream/

Initial debug turned up a dumb assembly mistake..– I swapped U1 & U2 despite the clear labels on the silkscreen. 

 

I hardwired the display inputs to only lite digit 1 and display an 8 (1000b). 8 because it's the digit which uses the most current given the largest area. This will allow me to verify the anode current before committing to a final anode resistor. To "latch" the 8 digit; I used my RatShack Logic pulser to toggle the LE pin.

 

I was able to empirically  calculate the Anode resistor using the built-in test point and pot. 21.4k... now I just need to find some 22k 603 resistors to make it work. 21.4k gives me 2.5mA of anode current which is typical for the NH-12A tubes I’m using. 

 

Here’s the top view of the display boards:

http://www.flickr.com/photos/52968060@N00/858242778/sizes/l/in/photostream/

And the money shot for the backlite display:

[]

 

I decided early on that I wanted the backlite to be purple rather than some other color because I thought it’d contrast nicely against the orange digits.

You can see the testpoint and Anode pot right below the Nixie tube. Obviously; these will be de-poped for “production” boards.

 

With the resistor calculated; I need to focus on creating a Display tester so I can run the display thru all the digits and functions.

[John Rehwinkel]

> http://forums.arcade-museum.com/showpost.php?p=2391595&postcount=43)

This is a nice writeup and a good-looking project! I'm really interested, as I'm a pinball aficianado myself. I really think the 3D effect of nixies would be
appealing in score displays.

> Initial debug turned up a dumb assembly mistake..– I swapped U1 & U2 despite the clear labels on the silkscreen.

Silkscreen? That looks like a protoboard. I'm unsure what U1 and U2 are anyway, most of those supplies only use one IC (the 555).

> I was able to empirically calculate the Anode resistor using the built-in test point and pot. 21.4k... now I just need to find some 22k 603 resistors to make it work. 21.4k gives me 2.5mA of anode current which is typical for the NH-12A tubes I’m using.

Make sure those SMD resistors can withstand the voltage - you may need to use two in series if not.

> I decided early on that I wanted the backlite to be purple rather than some other color because I thought it’d contrast nicely against the orange digits.

And it does - any any mercury haze is effectively rendered invisible.

> With the resistor calculated; I need to focus on creating a Display tester so I can run the display thru all the digits and functions.

This is where something like an Arduino comes in handy, as you can just use it as an easy-to-program logic level generator and have it cycle
through any patterns and sequences you like with not much effort.

- John

[Zitt]

On Saturday, March 23, 2013 10:02:51 AM UTC-5, jrehwin wrote:

> Initial debug turned up a dumb assembly mistake..– I swapped U1 & U2 despite the clear labels on the silkscreen.

Silkscreen?  That looks like a protoboard.  I'm unsure what U1 and U2 are anyway, most of those supplies only use one IC (the 555).

I was refering to the base board; not the prototype breadboard which has the 555 timer on it..  

> I was able to empirically  calculate the Anode resistor using the built-in test point and pot. 21.4k... now I just need to find some 22k 603 resistors to make it work. 21.4k gives me 2.5mA of anode current which is typical for the NH-12A tubes I’m using.

Make sure those SMD resistors can withstand the voltage - you may need to use two in series if not.

Gave it zero thought. Will verify.

 

> I decided early on that I wanted the backlite to be purple rather than some other color because I thought it’d contrast nicely against the orange digits.

And it does - any any mercury haze is effectively rendered invisible.

:D nice accident there, huh?

 

> With the resistor calculated; I need to focus on creating a Display tester so I can run the display thru all the digits and functions.

This is where something like an Arduino comes in handy, as you can just use it as an easy-to-program logic level generator and have it cycle

through any patterns and sequences you like with not much effort..

Good Call.

Initially I dismissed it because I had an “activewire” microcontroller board here which was collecting dust.

 

Turns out the activewire board only has drivers for WinXP... none for Win7.

While at Frys today; I saw they had some Arduino usb devices for fairly cheap. I ended up getting a Nano which had 14DIO pins – barely enough to drive the display.

 

A few hours later; I had a working Pinball Display tester:

http://youtu.be/kz3ikA82iH8

 

I’ll publish the code later; but thought you’d guys want to see the display functional asap.

Tests all the digits and the BLANK functionality which is between the 9 and the 0.

 

Next step is to desolder the current display PCB and build a fully populated display based on the latest PCBs. Once I have a fully populated display; I can test all the digits and the 7digit emulation capability. 

[John Rehwinkel]

> Silkscreen? That looks like a protoboard. I'm unsure what U1 and U2 are anyway, most of those supplies only use one IC (the 555).
>
> I was refering to the base board; not the prototype breadboard which has the 555 timer on it..

Whoops, I misunderstood!

> While at Frys today; I saw they had some Arduino usb devices for fairly cheap. I ended up getting a Nano which had 14DIO pins – barely enough to drive the display.
>
> A few hours later; I had a working Pinball Display tester:
> http://youtu.be/kz3ikA82iH8

Nicely done! I get a lot of mileage out of these inexpensive microcontroller boards. A friend had asked me about them a few days ago, resulting in my posting a "family picture", which I'll share here as well:

http://www.flickr.com/photos/23304890@N00/8572966925/in/set-72157626837690966/

> I’ll publish the code later; but thought you’d guys want to see the display functional asap.
> Tests all the digits and the BLANK functionality which is between the 9 and the 0.

Yeah, that's nifty, and it must be gratifying for you as well. I love when projects make progress.

> Next step is to desolder the current display PCB and build a fully populated display based on the latest PCBs. Once I have a fully populated display; I can test all the digits and the 7digit emulation capability.

I'm guessing you have the 0.156" connector pattern to match the connectors on the pinball machine (they do make nice use of standardization and modularity, making these mods ever so much easier). And naturally, you could put mating connectors on your tester and power supply to exercise your finished boards.

I'm having trouble deciding which machine I'd want to put nixie displays in. I have a Xenon and a Raven, and neither of them seem right for it. I was planning on replacing the Xenon displays with blue LED displays to match its blue-heavy "futuristic" design (I've already relamped the blue bumpers and tube with LEDs, and they look great). And the Raven uses VFDs, so isn't really a candidate. Which means it's time for me to buy another pinball machine! Or use nixies for the conversion I'm slowly building (I got a knackered Sorceress and I'm trying to create an "All Your Base Are Belong To Us" game out of the carcass).

- John

[Quixotic Nixotic]

I have a back box for a Bally Vector that is an unfinished project.

Bally made a few games with a double glass sandwich and animated incandescent lamps all around the edge, in between the two layers. Vector is one of them. Space Invaders and Xenon are two others.

I went as far as installing a power supply and building a driver board to animate the lamps, but could never think of enough things to do with the five display areas. Any bright ideas gratefully received, pun intended.

If anyone in the UK needs this back box to restore a machine, let me know. Many examples of Vector have suffered with the front decal delaminating and bubbling off the glass. My example has not suffered this fate. The picture is not of my box, but I can take pictures if anyone needs them.

Conversely, if anyone knows of a Vector body with no head, I'd buy that.

John S

[Zitt]

Work on the Nixie display has stalled because I can't seem to find the cause of a specific problem.

Last week I put the “Tested” nixie display into my Bally Star Trek; and sadly – only digits A4-A1 work. A5, A6 won’t light.

Tonight I cut the D5 trace between Q5 and U4; and hard wired from the pin2 side of R44 to the base of Q5 and Digit 5 lit.

This means that my logic must be flawed at U3A and U4; but apparently can’t see the forest for the trees.

 

Maybe a second set of eyes would indicate the problem? Anyone feel like looking for a bug?
http://www.Pinball-Mods.com/blogs/wp-content/uploads/2013/01/Bally7Nixie.pdf

The tester doesn’t indicate there is a problem; so wondering if it’s a timing issue I’m missing.

[Terry S]

The 4503 is an tri-state device -- do you need pullups on the outputs?
I can't tell from a quick glance how you are using it. How about
series resistors to the bases of the transistors? I see those on A1
thru A4. Without some series resistance your driver can only go to .7
(Vbe) and I'm not sure how well it will like being clamped that low.

On Apr 3, 11:31 pm, Zitt <zittw...@gmail.com> wrote:
> Work on the Nixie display has stalled because I can't seem to find the
> cause of a specific problem.
>
> Last week I put the “Tested” nixie display into my Bally Star Trek; and
> sadly – only digits A4-A1 work. A5, A6 won’t light.
> Tonight I cut the D5 trace between Q5 and U4; and hard wired from the pin2
> side of R44 to the base of Q5 and Digit 5 lit.
> This means that my logic must be flawed at U3A and U4; but apparently can’t
> see the forest for the trees.
>
> Maybe a second set of eyes would indicate the problem? Anyone feel like

> looking for a bug?http://www.Pinball-Mods.com/blogs/wp-content/uploads/2013/01/Bally7Ni...<http://www.pinball-mods.com/blogs/wp-content/uploads/2013/01/Bally7Ni...>

[GastonP]

I agree with Terry, you need to put some base resistors there. Your ubiquitous 9.1K will do. Of course, test whether the 4503 and the MPSA42s are still working. CMOS logic is not output short circuit proof, nor the MPSA42 can take too much base current.

Additionally, the 9.1K base resistors will protect the 4503 in case of an open EB junction failure in the MPSA42. This due to the 4503 output parasitic diodes.

Gastón

[Zitt]

On Thursday, April 4, 2013 7:03:19 AM UTC-5, Terry S wrote:

The 4503 is an tri-state device -- do you need pullups on the outputs?
I can't tell from a quick glance how you are using it. How about
series resistors to the bases of the transistors? I see those on A1
thru A4. Without some series resistance your driver can only go to .7
(Vbe) and I'm not sure how well it will like being clamped that low.

I'll look again; but pretty sure the 503 is a cmos device - not open drain.

I actually tried  a series resistor on at the base of A5; no impact. It was the reason I could wire the base to the series resistor to show that the digit works when the circuitry is bypassed.

[Zitt]

TI's data sheet says that the 503 is capable of sinking and sourcing current:

http://www.ti.com/lit/gpn/cd4503b

and the drawing shows N and P transistors in the output.

So the device isn't open drain.

at 5V; the device can sink (low) 2.3mA typical and source 1.9mA typical (high). 

Even with a minimum beta of 25 for the kathode drivers; IB would be 80uA given a 2mA emitter current.

[GastonP]

Zitt,

[GastonP]

Zitt,

   The problem is not that it is an open drain or a CMOS (it is a CMOS and I put it as so in my first email). The problem is that the base MPSA42 conected directly to the output effectively shorts the output to ground unless you put some resistance into that base circuit.

You say you tried putting a resistor in the base of the transistors to no avail. To avoid unpleasant sudden malfunctions, let the resistors there.

If you suspect a timing problem, try slowing the multiplexing to a very slow rate. That should let you see if there is something wrong with the logic. With no "conversion" the buffers are connected straight to the inputs so you should have no problem testing that part of the circuit manually.

[Zitt]

On Friday, April 5, 2013 8:01:34 AM UTC-5, GastonP wrote:

Zitt,

   The problem is not that it is an open drain or a CMOS (it is a CMOS and I put it as so in my first email). The problem is that the base MPSA42 conected directly to the output effectively shorts the output to ground unless you put some resistance into that base circuit.

You say you tried putting a resistor in the base of the transistors to no avail. To avoid unpleasant sudden malfunctions, let the resistors there.

Gaston,

Thanks for the feedback. While valid (regarding shorted A42s); this turned out not to be the cause of the problems.

More debug seemed to point to the 4555 1to4 decoder circuit.
I pulled the tristate buffer (u4) and solder bridged the outputs of the 1to4 decode straight to the transistors thru a 9.1k resistor.
The display does the same thing without U4.

This points to U3 (cd4555) being the culprit.

Now; given I’ve already verified 7 digit emulation with the arduino which doesn’t work in the machine; seems to be a clue.
I’m leaning toward the output of the MPU being TTL compatible; but not CMOS compatible. I don’t think the signal to the displays is meeting CMOS high requirements for digits 5&6. According to my mpu schematics; the digit enables are driven directly by the output of a 6821 PIA.

So; next step is going to be to wire in an oscope to see what D5’s levels are.

This pretty much sums it up:
http://www.flickr.com/photos/52968060@N00/8632599249/sizes/o/in/photostream/

PeakToPeak; my displays (digit enables) are only getting 1.6V for a high. Well below the cmos “good” for a 1. This is measured at R44 and R43 closest to the connector on stock displays.

This is the reason why my Nixie design isn’t working. I can design around this with either a transistor or some other translation logic; just not sure why the value is so low.
I see why it works on stock displays as all we need is for the high to be > ~0.7V to turn on the digit enable transistors in the original design.

Other pinheads confirmed their machines were also outputting ~1.8V for a high instead of the 5V I was expecting.

I did some "dead bug" rework to the existing display; basically epoxying two SMT 2N3904s to the top side of U3. I cut some traces and soldered a 20K ohm pull up between VCC and the collector of the transistors. Emitters were tied to ground. Bases were connected to the series resistors currently present in the schematic.

http://www.flickr.com/photos/52968060@N00/8638427889/sizes/o/in/photostream/

The goal here is to work out the kinks in the design so they can be incorporated into a FAB B board and be relatively confident the design will work out of the box.

Because the BJTs are single transistor inverters; I needed to rewire the input to U3. I wanted to reuse the existing CD4555B chip already present to keep the design simular. Turns out that by swapping A & B inputs vs the schematic; the following boolean logic become obvious:
U3A Q1 = !B*A = D5
U3A Q2 = B*!A = D6
U3A Q0 = !B*!A = D7
Remember that when the MPU is driving A5 or A6 high; the BJTs invert that to be an active low. So the boolean math makes it logical.

The result (finally):
http://youtu.be/c7Q9Ry00e2o

Here are some pictures of the display installed in my Bally Star Trek machine:
http://www.flickr.com/photos/52968060@N00/8638427991/sizes/o/in/photostream
http://www.flickr.com/photos/52968060@N00/8638427933/sizes/o/in/photostream

Known issues:

1) Digits are too light when running in multiplexed mode (in a real machine); plan to drop the anode resistor to ~2.7k from 22k to brighten the digits. Not a good idea for non-pinball machines which aren't multiplexing the digit enables; but should be fine for more machines.

2) Need to "fix" the native 7 vs emulated 7 digit jumper selector given the need to invert D7 in native mode.

[Zitt]

Updated schematics are posted here:

http://www.Pinball-Mods.com/blogs/wp-content/uploads/2013/04/Bally7NixieFabB.pdf

 

Fab B changes:

• Changes around D[5..7];
  • reworked for transistor inverters with pullups.
  • U3A rewired to enable proper output with inverted signals.
  • U3A always enabled  ( !E tied to ground ).
  • U4 I5 & I6 pull from Q1 & Q2 outputs instead of main connector so that cmos levels are observed at input of U4.
  • D7’s resistor moved to base of Q20 and reduced resistance given below.
  • D7’s non-emulated mode drives D2 which is now a SCHOTTKY diode so that lower Vf(D2) doesn’t impact ability to drive Q20 directly.
  • Additional Boolean math notes around U3A decode logic.
• As observed in Nixie newgroup (among others); Added R70 and R71 to bases of Q6 and Q5 to help protect cmos logic in the event of a shorted MPS-A42.
• Reduced VR1 from 110V zener to 91V Zener to keep “standby” voltage rail lower than Nixie striking voltages.
• Changed R62 to 1% 30 ohm resistor to enable LED current measurement via ohms law.
• Added J5 to R62 to enable pads for LED current setpoint measurements.
• Collector / Anode resistors reduced from 22K to 2.2k to enable brighter digits in multiplex mode.
• Stuffed anode/kathode standby resistors. Was empty, is 300k.
• Changed TP4 testpoint. Was 80V is 90V.

 

Please let me know if you see anything of concern.

[GastonP]

Hi again Zitt...

   All of the changes seem for good... but just for the sake of simplicity... did you try with only a pull-up resistor to the U3A inputs to see if you could bring the levels to CMOS ones? Actually, CMOS with 5 V levels are fully compatible with TTL ones, but when one wanted to be sure, a pull up to Vcc did the trick.

Regards

   Gaston

On Friday, April 12, 2013 2:14:31 AM UTC-3, Zitt wrote:

Updated schematics are posted here:

http://www.Pinball-Mods.com/blogs/wp-content/uploads/2013/04/Bally7NixieFabB.pdf

 

Fab B changes:

• Changes around D[5..7];

• • reworked for transistor inverters with pullups.
  • U3A rewired to enable proper output with inverted signals.

[Zitt]

On Friday, 12 April 2013 19:29:02 UTC-5, GastonP wrote:

Hi again Zitt...

   All of the changes seem for good... but just for the sake of simplicity... did you try with only a pull-up resistor to the U3A inputs to see if you could bring the levels to CMOS ones? Actually, CMOS with 5 V levels are fully compatible with TTL ones, but when one wanted to be sure, a pull up to Vcc did the trick.

 

I did. On the machine it seem cause more problems that solved.

For whatever reason; the pullup cause one of the digits to glow constantly and very brightly... not just on the nixie display; but on all of them.

Also; keep in mind the MPU board has a 1.2k series resistor on the digit enable lines; so unsure how that'd work properly.