1983 Scoreboard Problem(Period lights not lighting

[j4bs]

I just purchased a 1983 Chexx, and only the third period indicator lights (there are 3 LEDs per side). Nothing visibly wrong with either circuit board. Seems odd to me that one lights, and the others do not.

Wondering if anyone has any experience with these boards?

Thanks!

[akarr1122]

I actually have this same problem but instead none of my lights come on. Ive been looking for answers to this problem and the only one i have found is people have said to re seat all the pins inside the scoreboard and it fixes the problem.

Just curious if you have tried this? Also does ur fan and light work? Both of mine work

[shirkle]

A few things coming from someone who's never had this issue, but has worked on scoreboards before and has fixed arcade games before-
No lights at all:
Visually inspect the bulbs. You can check for sure by testing them for continuity too. If they test out fine, move on to the next steps.
Test the voltage going from the main PCB to the scoreboard. Should be about 12v. If your fan is running, then you already know you're getting 12v there. I believe it's a purple wire, and ground is usually black but may be grey.
If that's fine(or the fan is running), then I would attempt to test the voltage at the light when a game is playing. Just run your multimeter across the two quick disconnect tabs on each light since one tab is ground and the other is 12v. Remember, it will only be getting 12v during the period when it should be lighting.
If that's fine then you must have bad bulbs....which could have been visually inspected in the first place.
If it's not even sending 12v to the scoreboard, then you know you have an issue either at the main PCB, or in the power supply.
If it's sending it to the PCB, yet the lights aren't coming on, at least you know that you've narrowed it down to either wiring in the scoreboard or something on the scoreboard PCB. Check the wiring first. One bad ground wire would knock out an entire side of lights.

As for the guy with just 3rd period lighting: check the bulbs first.
If the bulbs look fine, then check the wiring. Like I said above, a bad ground wire connection would take out some lights because the ground wire is just daisy chained in there. If that's all good, then you've narrowed it down to a scoreboard PCB problem.

Let us know how your testing goes and we can take it from there.

[j4bs]

Resoldered the wiring and even though the original joints looked bad, no difference. I consider it a minor victory that the score still registers as before.

I plan on trying to follow the traces on the board to determine which ICs are for the score and which for the period LEDs. I'll update if I make any progress.

Thanks for the ideas so far.

[shirkle]

There are 3 PCBs in the scoreboard unit: one for the "I" "C" "E" lights, and one for each side's scoring LEDs.
Your focus should be on the ICE board, which is the one the wiring attaches to. On it there is one 74LS164 chip and three TIP120 transistors that drive the 12v "ICE" lamps (two lamps per TIP120). Replacing them should be cheap and easy if you're handy with a soldering iron. That's what I'd do, and I'd socket the 74LS164 if it's not socketed already. You could probably check the chip first for its voltage to see if it's actually bad, but if you have 12v going into the board, and the lights aren't lighting...it's probably a safe bet that one of those things is bad, probably the 74LS164.

If you've never removed an IC from a circuit board before, a nice trick I learned for beginners is to use a dremel to cut all of the legs off at the IC, remove the chip part of the IC, leaving just the legs. Then remove the legs one at a time by desoldering them one at a time. Not sure on your experience level, so I'm just throwing that out there.

Keep us posted.

[shirkle]

Just looked over a schmatic. Q2and Q3 transisters (TIP120) control the "I" and "C" that you're having trouble with. I'd start there since the "E" is already working.

[j4bs]

No luck, replaced all three transistors and the IC but no change in how it operates. I was reasonably sure the problem was on the board since the score works, and the third period lights.

Back to the drawing board. I do appreciate the help.

[shirkle]

Bad traces or solder joints on the board?
I'm a little stumped at this point.