What's a KAR board?

[shortrackskater]

Okay as you all know...or not... I have a perfectly functioning CEI Video Poker game. Just noticed a connector on the back panel that says "KAR BOARD."
What does the KAR board do? 

[SolidSilver]

Thought no one would ever ask 
The KAR board is an amazing device from Omega (who became CEI) that I've never actually seen.
KAR stands for Keep Alive Resistor: the board is intended to lengthen the life of all those
little incandescent switch bulbs by keeping a tiny current always flowing thru them, even when off.
The current is just enough to keep the filaments from going totally cold, but not enough for them to give off visible light.
Thus, the thermal "shock" to the filament is less when it gets switched on.

Does anybody actually have one in their CEI? Or have a schemo?

[shortrackskater]

Well that's the last thing I would have guessed! Interesting though... I had thought it was maybe for some kind of control/programming on the mpu. I wonder why they didn't just make that a permanent part of the machine? Cost, I'd guess on both ends. More costly to buy the machine with it, but in the long run the casino would save on bulb replacement and the subsequent down time of the machine? 

[arcade_jim]

Hola! I'm new to NLG, just bought a CEI machine that I'm trying to get up and running. It happens to have a KAR board so I thought I would post some pictures of it.

[SolidSilver]

So that's what the little hummer looks like; cool!
Thanks for sharing, Jim, and welcome to the site.
Post pics of your machine, and we'll be glad to help!

[shortrackskater]

Well I can certainly see they've done their job! Thanks for posting.
 

[SolidSilver]

Hmmmmmnnnn.......
Now that I see it, I notice it has 9 resistors, but 90% of these machines have 10 buttons.
Huh?

[shortrackskater]

Hang on Jim! I'll count my buttons right now! 

[SolidSilver]

I played with my Casino Poker 10-button machine, and think I have the answer:
thee 5 HOLD or DISCARD buttons are always either all on or all off. The KAR board
likely has one resistor for the group of them; that's the way I'd design it.

So, only 6 resistors required, plus 3 more for machines with extra buttons like
draw poker with the Double Up option.

[RPMcKenna1976]

Can someone out there with a KAR board help me out with measuring the DC Voltage? I have been troubleshooting a machine that has one and all of the button lights are dim.


The resistors all have continuity but two of them are missing most of the ceramic coating from time and heat. If I bypass the resistor with a line of solder some of the lights work nice and bright as I assume they should.


My KAR board measures 9.0vdc


If someone out there could help me to cross reference, it would be greatly appreciated.

[rokgpsman]

Can someone out there with a KAR board help me out with measuring the DC Voltage? I have been troubleshooting a machine that has one and all of the button lights are dim.

The resistors all have continuity but two of them are missing most of the ceramic coating from time and heat. If I bypass the resistor with a line of solder some of the lights work nice and bright as I assume they should.

My KAR board measures 9.0vdc

If someone out there could help me to cross reference, it would be greatly appreciated.

This is what I think is going on,,,

Below is a photo of someone else's KAR board with my notes, let me know if there is an error. Your KAR board is different since you have an earlier machine but it is similar enough I think you'll see how it works.

The machine does not need the KAR board installed, it is just there to prolong button lamp life. The button lamps get their power from the motherboard, it is about 12-16vdc I think. Your motherboard F3 fuses the lamp voltage, that's a handy place to measure it. You may have to use the neg side of the large black capacitor near F3 for a meter ground to get a good measurement. If it is 9vdc that is too low and explains dim button lamps when they are supposed to be bright.

When the button lamps are turned ON they get power from the mpu button circuit sending the 12-16vdc lamp power to them. When the mpu board turns the button lamp OFF the KAR board applies the lamp voltage to each button lamp, but it goes thru the resistors on the KAR board. The resistors reduce the electricity thru the button lamps to a trickle, so the lamps are slightly ON. Basically the KAR board just provides another way for the button lamps to get power when they are OFF, but that power goes thru the resistors on the KAR board so the button lamps are only dimly lit. When the button lamp is supposed to be ON for real it gets full lamp power from the MPU, the KAR board has no affect.

You KAR board is a little different since it is an early version, some later machines had more button lamps, needed more resistors. Some of the later KAR boards have a higher wattage white rectangular resistor and it takes care of 3 button lamps by itself. I didn't see any markings on it in the photo, may be out of view. You can resistance check each resistor on your KAR board, I think they should measure between 100-180 ohms. But remember, I don't think the KAR affects the brightness of the button lamp when the lamp is switched ON. That brightness would be set by the amount of your lamp voltage.

Below is a photo showing the resistor values I can read from the photo. If you can read the markings on the white resistor I can update the photo to include its resistance value.