Yep, that is the issue actually. Noticed that earlier today & unfortunately not a header pitch I can find, so something creative will have to be done there. The pitch on the old plasmas I think is 3.18mm (0.125").

Here's the idea I had. After unsoldering the gas plasma display, the holes on the 7-digit Bally look big enough for regulator 3.96mm headers. So as long as other Bally/Stern 6 & 7 digit display boards are like that, my initial thought is.. for support & to make wiring up everything else easier, have at least 2x of the 3.96mm headers on the "led display" pcb. Maybe one on each end.. and solder those in first to get the display lined up & to have the support. They could even go in "dummy" connection through-holes that aren't used. That way you get the display all lined up correctly & at the right height (again some things to work out to make setting height easy)

One you have it mounted like that, if there's then small wire connections for the rest of the connections that drop down from the display into the plasma footprint's holes.. it'd be easy to identify where each wire goes as the holes would align.

There's definitely going to be some out-of-the-box thinking on this one.

I found some 0.1mm headers that I thought might work (at least for a good amount of the run), but as soon as I typed in "right angle" I came up with nothing. Might be something out there, I'll do a bit more searching. I just know that the more odd-ball stuff, it's like good luck finding it cheap

Yeah, I'm with you on that.. I'd also want it to look clean and not have some huge mess of wires going all around the board. And there'd have to be incentive to going through the trouble of desoldering components off an old board, so price would be a factor. It may be best to leave it as a full kit and not even bother offering the assembled "led digit boards" since if you can desolder/repopulate the old display board, then soldering in 6-7x led digits and a few other things to a new board won't be an issue. Also, these would just have generic 0.8in digits with decimals, with the upside that they'd get the job done for less.

I'm fairly picky about spacing things. So digits will be spaced evenly, they'll line up with where the existing displays were. I'll try and have it so it's easy when assembling to get everything all lined up. If I can't make all that happen and get the price somewhere people would want it, then I won't do them.

So with that said.. what if the price was at or under $100 for a conversion kit for a set of 5x displays? Just throwing out some numbers.. but I do realize price will be a factor on these.

Update: After looking at some digit pricing, RED digits are the cheapest [seems typical of anything led related]. Other colors may increase costs a good amount. Also depending on mosfets, etc components.. costs may be a bit more than I originally expected. I'll attempt to hit something that's appealing given the nature of this type of "DIY" project, but if I can't I'll possibly figure something else out (as far as just offering boards with digits and people can source the remaining components themselves, etc).

Haha.. nah, not bad news at all. Can't beat having a reserve of displays in case one goes out!

Some more progress this morning.. connected the rest of the digits. Guess all those years of fooling around with full-blown led display ideas that didn't really go anywhere paid off some lol.

Currently it's just using some transistors, but I'd like to get an idea of current draw with that setup first.. then possibly switch over to mosfets on the drivers. Part of what's making this possible too is having done load tests on Classic Bally/Stern machines recently, which allows me to gauge how the circuit's actually working & compare with what else is out there. Worst case, if it's like some of the led sets where it'd be better to have a 5A regulator on your SDB and you only have the 3A, then this switching regulator project could be an option for that.

diyled2_(resized).jpg

Excuse the cruddy quality of the video.. just used my camera for this and apparently it's horrible resolution in video mode

Always learning something Think I figured out why the "less than efficient" aftermarket displays I was testing was so power-hungry. Seems to do with transistor gain and saturation voltages. Found that out the hard way since it happened with the components I was using as well. Measured a rather large in-rush of current of several hundered mA on power-up, then it would settle down. Tracked that down and it's looking a lot better. Some more things to tweak I think, but getting closer to making this happen!

Yep how I feel enough times haha.

Yep, if they haven't already been tossed. I'm sure tons and tons of these boards in the last 5+ years have been thrown away because of the cost of the replacement plasma displays versus just buying a brand new led display.. and very small value the dead boards have other than for parts or for someone that stocked up on plasma displays when they were cheaper. Joe Homeowner with limited space that gets a machine to fix up, with 4x bad displays in it.. probably isn't going to hang onto too many dead displays before either giving them away or throwing them away.

It's really nice to see some other people like this idea And it's coming along.

I'm gonna try out some white led displays with the vinyl.. I was experimenting with that 4 years ago when I did this piece of art You can actually see a small piece of vinyl over the single digit in the breadboard in the 2nd photo up from the bottom. I think I was turning an amber led into orange. You're limited with color of the led segment itself and the color wheel... but going with white segments.. you can change the color to whatever the vinyl is.

Created a project page (and waitlist!) for this over @ http://www.pinitech.com/lab.php

For those that expressed interest.. and for anyone interested that hasn't commented.. if you could get signed up on the waitlist, that'd give me a better idea for the size of the initial board order. I'll probably order 50x boards minimum, but those could go pretty quick if a few people want a full set [which I'd imagine at least a few people might]. I don't want to go too nuts with quantity because waitlist numbers still aren't anywhere near actual initial sales (and this is still relatively new as a way to gauge orders/materials) but also don't want to underestimate too much either.

Put in the number of boards you'd need per however many sets you think you'd order initially. So if you'd order 1x single display conversion kit just to try it.. that's fine, just leave the quantity as one. If you'd want a single set to have enough for a single machine (5x displays) then enter 5x.

Again, for pricing I'm targeting $20.00 per display or less (full conversion kit that includes the new "plasma replacement" digit board + components, and also components to repopulate the old display board). Will probably separate those so that the people that want to order the components to repopulate the old boards can do that. There would also be discounts for full sets (ie. 5x displays).. and possibly further discounts for multiple sets.

Working on engineering on this thing a bit. So there's going to be 13 signal connections from the plasma footprint to the led digit pcb for a 7-digit display, 12 signal connections for a 6-digit (ie. you won't have to solder 30-40 pins for the "plasma" glass replacement). Then I want some support on the "led digit" board. As I mentioned previously, I'm thinking that could be done with 3.96mm right angle headers spaced evenly.. 2x on each side maybe. They could go in unused holes on the plasma footprint.

Another option would be using small right-angle brackets for support and using the existing screw holes on the display board. That'd be ideal as it may also allow for separation of the two boards instead of having them soldered together (depending how the other signals are brought over). Anyway, not sure where to look for brackets. Looking like I'll need one end of the right angle to be 15mm with the screw hole about 4mm from the end. The other end doesn't matter, could be any length.. just need to know where to put the hole in the PCB so I can set the height of the digits appropriately. I'd also want the bracket to support threading of a screw.. so I don't need a washer/nut on them. Anyone know where I can easily look for something like that?

Thanks!

The 7-digit Bally board I'm playing around with, there's 22 transistors and about 36 resistors that were replaced to move over to a 5v circuit with common low voltage NPN/PNP transistors. Even if it stayed at that, I'd have some technique suggestions on removing the components that would make it quite a bit easier. But I'd rather reduce the component count further. I'm sure it can be done [at least to some extent].

I'm actually wondering if I can get away with leaving the 2n5401 and MPSA42 transistors in the circuit. Those are higher voltage rated transistors, but they operate off a 5v base voltage. I'd just be replacing them with lower voltage rated transistors, so I'm not even sure they need to be replaced. Haven't tried leaving those in there yet, but it'll be part of a 2nd trial design. That would reduce the components to be replaced by over 1/3.

Datasheets:
2N5401 - http://www.onsemi.com/pub_link/Collateral/2N5401-D.PDF
MPSA42 - http://www.onsemi.com/pub_link/Collateral/MPSA42-D.PDF

The ~36x resistors being replaced.. 7x are getting replaced with 0 ohm resistors and could just be jumpered over instead of removed. There's another 15x you could solder a resistor in-parallel to the current resistor and get to the value needed, instead of removing the original resistors.. it'd be another option that could save some time.

This has been kind of an iterative process. First step was to see if I could use the existing footprints and not have too many hacks to get the component board converted over to something that could drive an led board connected to the plasma footprint. Then there's reducing component count on what needs to be replaced and/or removed. Then there's the design/engineering for making the led digit panel (plasma glass replacement) as easy as possible to wire up & get at the correct height, as well as giving it support... and ultimately making the whole thing look nice.

Open to suggestions on any of this. I'll likely be trying with leaving the higher voltage transistors in-circuit on another board early this week, but if someone knows why that wouldn't be a good idea.. or wouldn't work, let me know.. it'd save me some time

Soo.. don't want to get hopes up too much... eh who am I kidding

I left the original transistors in there, and aside from what I think will amount to tweaking transistor gain.. it's working! At first a few of the digits weren't as bright as others, but with a tweak to the base resistor on the 2N5401 digit drivers, they now look better. Still a very slight difference, so I'll keep at it!

There was no big in-rush current when I started this up in the game, stayed right around 1.6A that I found was typical load for the boards in Nitro Groundshaker. Looks like it might fall somewhere in about 70-85mA measurable current usage when in the digit tests. I'll have to verify that. Some other aftermarket displays were 36mA, while the worst case one was 228mA!!

And as for limiting the number of modifications -- I cut one zener diode off the board and unsoldered 7x resistors to replace those with higher value (couldn't get there by putting resistors in parallel since they were too low a value). There were then 7 jumper wires on the back of the board and 14 resistors to solder in parallel to other resistors on the back of the board. That's it! This greatly simplifies the conversion process. It's almost too easy

front_display_(resized).jpgbackdisplay_(resized).jpg

Pictures posted!

I didn't think it'd be possible to convert one of these without a mess of wires or some kind hacks if using existing footprints on the component board. I was happy enough getting there. Now, with minimizing what needs to be unsoldered with through-holes cleared to 7x resistors, and then having the ability to just jumper and solder parallel resistors in on the rest of the stuff.. that's a game changer. It would allow just about anyone with soldering ability an easy way to do the modifications to the component board, with minimal tools (ie. don't necessarily *NEED* a Hakko then). The rest is connecting the led digit panel.. which I'll make as straight-forward as possible.

EPIC in my eyes.. I hope it stays this way! Like I said, don't want to give *too much hope* here, but so far.. so good!

Might be splitting the difference some in what gets replaced on the component boards..

I've been playing around with this 2nd way of converting the boards, with leaving more of the original components & although it was working fine there were a few digits that weren't as bright. Attempts to correct this proved futile.. even tried narrowing down the issue by cutting a few of the transistor legs and piping everything before the digit driver over to a different digit driver, and as far as I can tell.. it was just the digit drivers themselves. So either variances in the transistors causing a slightly different gain or slightly fatigued (if that can even happen) or possibly just that using discrete transistors as current drivers with multiplexing isn't a perfect science as far as uniform current use among digits (whereas it may be more-so if using ICs like ULN, 74HCT244, etc). One other interesting thing was some of the digit drivers had F585 markings (Fairchild?) while others had M585 (Motorola?). Unfortunately the couple of digits that were noticeably dimmer happened on both markings, so couldn't blame it just on different manufacturers.

After replacing the 7x digit drivers.. current usage per digit are more in-line with one another and my eyes aren't picking up any differences either.

How's this look to everyone for a 7-digit design?

bally7digitretro_(resized).jpg

I think this should allow for some versatility in mounting. First of all, there's holes for a right-angle bracket for support, the other end of the bracket would align with the pre-existing holes on an original Bally/Stern component board. It looks like it'd set the display depth to about exactly where the plasma glass sits (considering the thickness of led digits I'm using to gauge).

There's then a set of smaller headers at 2.54mm pitch that you could use 0.1" right-angle header pins on, and normal 0.1" Molex connectors (other end of the wires would get soldered directly to the component board's plasma footprint positions). This would allow removal of the led digit display panel from the component board. I doubt it's a huge concern for too many people, but it doesn't cost anything to throw an extra footprint on the board & allow for the option.

Then there's the 3.18mm pitch header that matches the plasma header on the component board. This would allow for easier wiring since the footprints would match up. I removed any unused/extra holes on the footprint. Small wires could be used to wire between the component board & display panel, or I'm pretty sure you could also use SINGLE 3.96mm right-angle headers (at least on Bally boards whose plasma through-holes are large enough to fit a 3.96mm pin) and still have the display sit at the correct depth. I may add some or all of the unused plasma holes back in in case people want the ability to use them for additional support. Anyway, this should all give plenty of options on mounting that suits your needs/budget. LMK what you think!

And here's the 6-digit..

bally6digitretro_(resized).jpg

One other thing to note... on the header that matches with the plasma one.. I left duplicate connections on there (ie. each plasma display had 2x pins for the digits.. not sure if that was due to current use or what). Anyway, figured leaving them there will be good as an extra precaution if a solder pad is "iffy" and you still want to wire 1-to-1 (having the small wires connecting both boards just go straight out and down to the plasma footprint). Again, doesn't cost anything.

But.. there will be 15x connections to be made for a 7-digit and 13x connections for a 6-digit.. to connect the display panel between both boards. Any of the additional are just extra connection points for the digits enable lines.

Ah, but the only way I see any header being used is to create something custom..

One possible option is to use 1x2 (ie. single position, dual-row) right angle 2.54mm headers. They'd get soldered in vertically with 3.18mm pitch between them (picture the plasma footprint in the boards I posted above, with another of the same footprint below it spaced 2.54mm apart vertically). This would create the custom 3.18mm pitch needed to mate both boards. Having the 2.54mm headers initially as 2x vertical pins would eliminate the usual issues with trying to align a single pin at the correct angle. Once soldered in, you'd have to cut off one pin from each 2pos header (effectively creating a single row of pins needed for mating with the plasma footprint). So you'd have 13x or 15x of these 1x2 headers to solder in, but that seems like it'd go relatively quick.. and it'd then eliminate running separate wires/harness for signals. The boards could then just be mated & soldered together. The only thing is, the led digits wouldn't sit as far back (3.96mm right angle pins push them back further than 2.54mm pins) and the right-angle bracket for additional support probably couldn't be used. So as far as support, I'm not sure if 13-15x soldered 2.54mm connections is adequate enough.

Another option would be a narrow adapter board. The adapter board would again use 2pos 2.54mm headers at 3.18mm pitch between them for alignment, but this time they would be straight headers. Depending on 6-digit or 7-digit, 13-15x of those 2pos headers are soldered in, you again cut off one side to create as single row for mating. This small board gets plugged into the Bally/Stern plasma footprint. On the reverse side is a "normal" connector foorprint (or two). So then the digit panel plugs or unplugs with normal connectors on it. I'd think the bracket could still be used for support. That one would be even more of an exact science though in design. It'd also add a bit to costs with having another pcb as an adapter. That said, it could be an "optional" way of doing things.. and an optional cost.

This is all as a 2nd option instead of running individual wires. I guess I figured 13-15x individual wires per board isn't too bad. They'd be maybe 1" long if you were mating 1 with the plasma footprints.. or 3-4" if going to the alternate 2.54mm footprint that would allow for a disconnect.

Cool Yeah that's very true with the Tee-Pee setup as you described. Push the wires through and solder them in without flipping the board around any more. Should make it pretty painless.