(Topic ID: 49434)

LED lights in Bally 1978 SS game - new board required??????

By rufessor

6 years ago

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  • 78 posts
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  • Latest reply 1 year ago by rufessor
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#7 6 years ago
Quoted from Pac-Fan:

2) Cause additional current to be pulled without creating light (or heat) to the level the SCR needs at a minimum. This is as simple as soldering a single, 470 ohm resistor across every single switched lamp socket underneath.

^ this is for controlled lamps only
I just solder chip resistors across the LEDs themselves - keeps the game original to easily go back to incandescent bulbs. If you don't have the soldering skills to do this then you will have to solder the resistor across the sockets. Never had a problem with ghosting or flicker.

If you have flicker on the GI in old Ballys this is totally different, this is the GI AC supply from the transformer that causes this. I think the "No-Flix" brand bulbs might help this.

3 months later
#45 6 years ago

This is not difficult at all - I modified a 19777 Bally Strikes and Spares in an evening with a soldering iron and a magnifying lamp. A few dollars in chip resistors, no special add on board. I modified the LEDs so to keep the game original and it WORKS PERFECTLY. The original reference doc is below:

"Once upon a time there was a led that flickered when it was installed
in an older Bally or Stern pinball machine. The LEDS flickered on any
machine that used a Bally As2518-14, AS2518-23, or Stern LDB-100. These
lamp driver modules were used from 1977 thru 1989. These boards use SCRs
to switch # 44 Lamps on and off in pinball machines. This has worked
well for many years, until someone tried to use a led instead of a #44
lamp. The LED flickered. I discovered that the reason the led flickered
was that the LED drew no current below it’s forward bias point that it
would not hold an scr latched. If a resistor is added in parallel with
the led, it would draw enough current to keep the scr latched and there
was no flicker. (Life is Good). Through testing I found that a 470 olhm
resistor was more than enough to keep any of the scrs that I tested
latched. The 470 olhm resistor can be added in the socket of the led,
soldered across the lamp socket, or soldered on the lamp driver module.
The electrons don’t know or care where the resistor lives, as long as it
will cause a 1ma load to the anode of the scr. All 3 ways have been done
and they all work well." - text by Ron Googe."

#48 6 years ago
Quoted from rufessor:

Cool.. I think I will just mod the connectors... Since I am re-pinning anyhow this is no trouble whereas re-pinning plus dealing with sockets is 2x the work and a more permanent mod and I have no interest in dealing with the LEDs themselves. Great quote...
SORRY for the confusion, I had not THOUGHT through my proposal to put it in series... my bad... Thank god my day job does not involve circuit design (who would have guessed?!)
Simple-stoopid but I stand corrected and happy to have an easy, viable, mod to accomplish.

Yes, dealing with the LEDs themselves is a bit of a PITA. My eyesight is getting worse with age and spending an evening under a magnifier with chip resistors to solder them on the LEDs is a hassle. It was worth it though. Good luck.

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