(Topic ID: 268498)

Weird occurance with insert lights


By spandol

22 days ago



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  • 27 posts
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  • Latest reply 12 days ago by spandol
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#1 22 days ago

I have a Big Game I'm working on. It had an Alltek Solenoid driver board, and I just put in an Alltek MPU and Lighting boards. I'm having something strange happen though. A few of the insert lights flicker in a consistent pattern (Video link below). I have the wire installed on a control light on the backbox lights to allow the lighting board to work with LEDs, which I have on the playfield.

I thought it could be a bad socket so I replaced that, but it didn't fix the issue. I always tried a different LED, but that didn't help either. Only other thing I can think of is a connection somewhere, but would it be such a consistent pattern if it were that? So, maybe its something to do with the LED board? I tried a different control light for the LED cable, but it didn't change anything.

If you guys know what's possible going on or what to try, please let me know.
Thanks!

https://www.dropbox.com/s/r820uciwcz0v9cu/IMG_2813.MOV?dl=0

#2 22 days ago

I tried another Alltek light board with the same results. I also wrote them to see if they have any ideas.

#3 22 days ago

Do they do that in game as well, or only during the test?

#4 22 days ago
Quoted from Xenon75:

Do they do that in game as well, or only during the test?

In game as well.

#5 22 days ago

Dave from Alltek contacted me. Let’s see if it has to do with this particular game and their board. I’ll report back.

#6 22 days ago

It really shouldn't but yes I am curious what he has to say.

#7 22 days ago

I used a half-dozen LEDs in my Stern Lightning with original boards but they did a much much faster on/off flicker. The resistor trick across the sockets fixed it. Yours flicker comparatively much slower. You might try just touching a 1.5 K resistor across one socket and see if changes anything. When I added a few LEDs to my early 80s Wms and Bally games from around that era, never had any flickering effect.

#8 22 days ago
Quoted from frenchmarky:

I used a half-dozen LEDs in my Stern Lightning with original boards but they did a much much faster on/off flicker. The resistor trick across the sockets fixed it. Yours flicker comparatively much slower. You might try just touching a 1.5 K resistor across one socket and see if changes anything. When I added a few LEDs to my early 80s Wms and Bally games from around that era, never had any flickering effect.

Thanks for the info. Mine did flicker quickly until I put the jumper wire from TP13 to a control lamp, as the manual details. Then the bulbs stopped flickering, except 6. Funny thing is, it’s all 3 inserts near each set of drops that say 25000. But that may be coincidence, as the 2x insert, reserve bonus and extra score for each completed line, also have that shorter flicker.

I’ll see if I have a resistor.

#9 22 days ago

And when they turn on during play and do that, or during attract, the flashing is exactly the same, that steady even blinking? But hmm if all your other control lamps are LEDs too it's probably not like my Lightning problem after all. Weird that it is so evenly on/off/on/off like a special flashing LED would do.

#10 22 days ago
Quoted from frenchmarky:

And when they turn on during play and do that, or and during attract, the flashing is exactly the same, that steady even blinking? But hmm if all your other control lamps are also LED it's probably not like my Lightning problem after all. Weird that it is so evenly on/off/on/off like a special flashing LED would do.

Yes, it is the same during a game too. That’s what makes me think it’s not a connector issue because of the same blinking. After some research it seems it may be that the light isn’t getting enough power so it’s shutting off, but the mpu keeps telling it to turn on. I don’t understand it completely, but the resistor might help. Tomorrow I’ll see after I talk with Alltek.

#11 22 days ago

I cannot find the original post, but there is a known issue with some Stern ROMs where the Lamp Update code is too close to the zero-cross interrupt. If I recall, it only affects the first handful of lights that are commanded to turn on - as time passes from the zero-interrupt, rest of the lights are able to latch the SCRs and stay lit.

Meteor is a known example of that, and the Rocket 1 bonus lights.

The only thing you can do is add a lower-ohm resistor to the insets (I went with a 220ohm), which fixes the issue.

Edit: And darnit, I wish I could find the original post where this was mentioned.

#12 22 days ago

Probably a post in the thread about my LED adapters, but yes the Stern MPU-200 games have issues with a few locations due to software timing, and Meteor is a prime example of that. I've moved to lower and lower resistor values over time to mitigate it but some games just need the additional resistor.

-Hans

#13 21 days ago

I found in talking to a Dave from Alltek that I’m not getting enough power to the lights. I’m reading between 4.8-5.1V. I’m almost done replacing the rectifier board with new connectors and will report back.

I’ve seen some weird stuff with rectifier hacks, but I’m scratching my head with this one. There was no need to extend these wires so I’ll be taking these off.
973D9185-B8F9-4C93-BEA9-AFE650954814 (resized).jpeg

#14 21 days ago

Found the video snip I took of my Lightning before I added the shunting resistors. They flickered badly, except for one which did indeed blink three times during each flash in the lamp test like in your video.

#15 20 days ago

Ok, i have a Lightning too, but haven’t converted it over to LEDs. I’m not too clear on resistors though, and what’s it’s actually doing to help. I have 100k Ohm 1/2 Watt resistors. Are these ok to use if I find I need to?

#16 20 days ago
Quoted from spandol:

Ok, i have a Lightning too, but haven’t converted it over to LEDs. I’m not too clear on resistors though, and what’s it’s actually doing to help. I have 100k Ohm 1/2 Watt resistors. Are these ok to use if I find I need to?

Simplified explanation:
So SCRs work by 'latching' - once told to 'turn on', they will STAY on, until the current flowing through them stops.
This means that say, for example, if you told a SCR to turn on a light bulb, the bulb will stay lit - even if you stopped telling the SCR to turn on. And the bulb will STAY lit, until you pulled the bulb out (or cut a wire, the bulb burnt out, etc.) The bulb wll then stay off until you tell the SCR to turn on again.

Bally/Stern games operate by - every zero-crossing (that is, when the voltage of the Lamp Voltage drops to 0, because, AC wave), the CPU will tell the lamp board what lights should be on. This will happen about 120 times a second (100 times a second for those in 50Hz territory.)

Incandescent bulbs draw a lot of current (compared to LEDs) - they draw enough to "latch" the SCR on. LEDs to NOT. So, the flickering you see is the CPU telling the SCR to turn on - and then the SCR turning off immediately because there isn't enough current to latch it on. Adding a resistor - in parallel increases the current that flows through the SCR to cause it to 'latch'.

A 100k resistor will not be low enough - will not allow enough current to flow to cause it to latch on, sorry.

#17 20 days ago

To sum up on the above - the reason it happens on SOME lights, and not others - like in Meteor and the Rocket 1 Bonus is because those lamps are the first ones told by the CPU to turn on.

If you look at an AC wave, it looks like this:
pasted_image (resized).png
When that line hits 0, the CPU starts telling the lamp board to turn on lights. The very FIRST LIGHTS it tells, the voltage may be a small fraction of full. (Say, off the top of my head, 1v instead of the 6.xv) Even with a parallel resistor, not enough current flows, so the SCR still doesn't latch. But as that wave grows up, voltage increases, the later lamps are told to stick on, and STAY on, because now there's enough current.

Note that the low voltage can cause this too - for example the same reason - if the lamps are only getting 5.3v, the resistors built into LED driver boards/adapters may still be too high to allow the proper current through to latch the SCRs.

#18 20 days ago
Quoted from Coyote:

To sum up on the above - the reason it happens on SOME lights, and not others - like in Meteor and the Rocket 1 Bonus is because those lamps are the first ones told by the CPU to turn on.
If you look at an AC wave, it looks like this:
[quoted image]
When that line hits 0, the CPU starts telling the lamp board to turn on lights. The very FIRST LIGHTS it tells, the voltage may be a small fraction of full. (Say, off the top of my head, 1v instead of the 6.xv) Even with a parallel resistor, not enough current flows, so the SCR still doesn't latch. But as that wave grows up, voltage increases, the later lamps are told to stick on, and STAY on, because now there's enough current.
Note that the low voltage can cause this too - for example the same reason - if the lamps are only getting 5.3v, the resistors built into LED driver boards/adapters may still be too high to allow the proper current through to latch the SCRs.

Thanks for this explanation. EE was actually my favorite class in college, but I didn’t need to go further. The one thing i don’t get is, if you need to provide more current to the LED to latch, isn’t a resister limiting the current more? Probably a noob question, but....

So, this must be the reason my game is flickering on some lights. I changed out the rectifier board and all connectors for it. No change. If I get the correct resister, say 220 ohms, and I only have one lug on my socket, where do I solder the other part?

Thanks again for the help.

#19 20 days ago

I’m kind of surprised it’s not working too, because now I measure 6.2 V on the lights where before it was 4.8-5.1.

#20 20 days ago
Quoted from spandol:

The one thing i don’t get is, if you need to provide more current to the LED to latch, isn’t a resister limiting the current more? Probably a noob question, but....

Check this out: https://www.swtc.edu/Ag_Power/electrical/lecture/parallel_circuits.htm
It's how parallel circuits work.

Quoted from spandol:

If I get the correct resister, say 220 ohms, and I only have one lug on my socket, where do I solder the other part?

The resistor should connect the two wires - on Meteor at least, one of the wire *may be* a braid attached to the foot of the socket. This is where one end of the resistor would go to. The other end would be the lug with the other wire.

#21 20 days ago
Quoted from Coyote:

Check this out: https://www.swtc.edu/Ag_Power/electrical/lecture/parallel_circuits.htm
It's how parallel circuits work.

The resistor should connect the two wires - on Meteor at least, one of the wire *may be* a braid attached to the foot of the socket. This is where one end of the resistor would go to. The other end would be the lug with the other wire.

Thank you very much!

#22 20 days ago

Thanks, the science makes sense now.

#23 19 days ago

So, very strange. As a test being suggested by Dave at Alltek, I switched the control wire of one bad lamp with a good lamp. At first it showed it moved with the wire. Then after a bit, both lights worked as well as 3 of the other bad lamps. So this left me with 2 flickering lamps. He asked me to try another Alltek lamp board, which I did. Now all the lights work. When I went back to the other board, the same 2 lights would flicker, so I’m back to the different board. I measured the SCRs on the flickering board, but they all check at 470 ohms.

So, now I’m good. When I use this other new board that didn’t work in Big Game, in my HG, let’s see what happens. There’s a lifetime warranty so I’m good.

Anyone know what might be wrong? Could the SCRs still be bad at 470 ohms?

#24 19 days ago

Actually, scratch that. 4 leds have gone back to flickering. I will try the resistors when they come in the mail.

#25 19 days ago
Quoted from spandol:

I’ve seen some weird stuff with rectifier hacks, but I’m scratching my head with this one. There was no need to extend these wires so I’ll be taking these off.

Likely they took parts from a less-burnt up harness to replace the burnt connector that was there or missing.... pretty common operator hack from back in the day.

For some reason, people never seemed to be able to get the proper pins and crimping tools then.

#26 19 days ago
Quoted from slochar:

Likely they took parts from a less-burnt up harness to replace the burnt connector that was there or missing.... pretty common operator hack from back in the day.
For some reason, people never seemed to be able to get the proper pins and crimping tools then.

I thought that, but did games have a pink wire or multiple same colored wires back then? I guess so!

#27 12 days ago

Ok, put 470 ohm resisters in the game and it solved the issue, except for one. One control light that was having the issue now stays on at all times. I checked the scr and it shows 470 ohms. What component did I blow?

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