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(Topic ID: 165157)

*Feasibility Study* DIY Allied Leisure LED Displays (using old boards)


By balzofsteel

4 years ago



Topic Stats

  • 5 posts
  • 3 Pinsiders participating
  • Latest reply 4 years ago by balzofsteel
  • Topic is favorited by 3 Pinsiders

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#1 4 years ago

There's at least one thread on here about "unobtanium parts". If anything qualifies for that title, it would be the 5-digit plasma displays used in first-generation Allied Leisure pins. Right?

IMG_0495_(resized).JPG

Here's a pic of someone's Boogie:

boogie_(resized).jpg

Player one works. Yay! Player two looks like mine did when the 5V regulator was putting out 1.2 volts. Probably not a tube issue, thankfully. Player three is covered by the price tag and four is dark. Looks like someone's pin is short a couple players. Good thing it ain't mine - two dead displays would bother the heck out of me. (part of the appeal of Dyn O' Mite was only having 2 displays to fuss over)

So anyway, I was doing something forget exactly what to the game and looking at the schematics - and lingered for a bit on the Standard Digital Scoring Unit page. Looking at how digits and segments are driven and how that didn't look like newer computerized pins. The Allied SDSU controls each segment of each digit separately. They're not multiplexed like they would be if there was a CPU to do fancy stuff like that. Stared at that for a while and wondered how hard it would be to make the board run LEDs instead of the plasma tubes.

Turns out it isn't terribly difficult. (or so he says)

See:

IMG_0492_(resized).JPG

Player one here has a LED display of my own concoction.

Went and found a datasheet for the DS8880 chips that drive the plasma display segments. It doesn't say anything about LEDs. The diagram looked like the chips drive segment cathodes and power goes to the tube anode.

Went looking for some cheap LEDs to play with and settled on these: http://www.taydaelectronics.com/led-displays/7-segment-1-digit/led-display-7-segment-1-digit-1-inch-common-anode-yellow.html They were out of red.

5 LED digits fit on one of these boards: http://www.taydaelectronics.com/hardware/prototyping-boards/prototyping-board-142x74mm.html

Back to the picture... Note that the ones digit is a fair bit dimmer than the rest. This was my attempt to drive LED with DS8880 IC. DS8880 is a HV plasma tube driver not an LED driver. oh well.

Back to the datasheets. More TTL Madness. There are LED drivers that are nearly pin-compatible with the DS8880, namely the 7447 and 7448. The 7447 drives 'common anode' LEDs and I have a few around. Back to pic - see how 6 and 9 are missing their tails? A 74247 would put those back. Didn't have any. Mouser and Digikey and Jameco have 74LS247 available - might get some sometime. I know there is a difference but do not know if the difference is important. (Wood Shop, Metal Shop, Auto Shop but no Electronics class) It would be nice if the LS chips could give the 6 and 9 their tails back.

The tens digit is dimmer than hundreds+ as it is being fed less voltage. The datasheet for the LEDs says they run between 1.9 and 2.5 volts. Tens is at around 1.8, hundreds near 2V and the rest at around 2.4V .

Here's some LEDs on a board:

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I trimmed the bottom corners slightly to set the board in the socket. I sanded off the plated lettering and a couple rows of holes to prevent shorts.

Here's the back:

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Piggyback adapter allows 7447 to sit on DS8880 and drive LED:

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The pieces:

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16-pin IC socket gets stuffed on top of DS8880. Machine pin type stuffs on tighter than cheap single-wipe socket. Made next layer from SIP strip socket. Nip off pins 3 and 5 as these aren't needed. Pins 9-15 are wired to LED segments. Wire lead from pin 16 feeds LED anode through a dropping resistor. Somewhere in the 150-120 ohm range seems to work.

This is a true DIY project as I have no plans to etch boards or source kit bits.

Rock On!

#2 4 years ago

Great work and nice write up!

#3 4 years ago
Quoted from pinball4ever:

Great work and nice write up!

Thanks. Hope someone can use it.

#4 4 years ago

Nice proof-of-concept.

Ideally, a final product would just be a plug-n-play replacement for the display PCB. With the work you've done so far, do you think everything for a new LED display could be contained on a self-contained display PCB?

#5 4 years ago
Quoted from ForceFlow:

Nice proof-of-concept.
Ideally, a final product would just be a plug-n-play replacement for the display PCB. With the work you've done so far, do you think everything for a new LED display could be contained on a self-contained display PCB?

Almost. If I was doing a permanent thing here, I would have pulled the DS8880 chips and put the 7447s in sockets, saving the old chips in case new tubes become available.(lol) Can't think of a way around that. Then the LEDs and dropping resistors could be put on a board. 5 digits and 5 resistors and that's it. Not a tough board to draw out, I just didn't do it. It wouldn't be terribly difficult to mod the OEM board, once the defunct plasma tube is removed. I didn't have any of those to mess with either.

It would definitely clean up the thing to get rid of the jumper wires and put the edge connector back in use.

Curiosity largely satisfied, now I need to figure out why bonus doesn't add. LED on p/f control board blinks when targets are hit but not on bonus board. Probably a backbox connector. Time to order some Mate-N-Lok pins.

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