Need help with schematic and ID of a chip

[uniman]

First of all I have very little experience with board repair. (as you will soon see)
I have a Universal 8304 video poker with a constant RAM error, even after a clear. Sometimes the program runs away on startup activating every output on and off. Quite a site to see!
My untrained eye thinks the Quad nand gate chip is the trouble. Why? Because there is no resistance between input voltage pin and ground pin.
Is this a logical assumption?

Looking at the chip it is a TC40H000P and also has stamped on it 8416H.
When I lookup the TC40H000P I see this datasheet. But when I look at the Universal schematic I see something different. The upper left gate is not a nand. What is it? An XOR?
Is this some sort of special chip or will a standard TC40H000P work as a replacement? I cannot find any reference to the 8416H.

[KirkLasVegas]

First of all I have very little experience with board repair. (as you will soon see)
I have a Universal 8304 video poker with a constant RAM error, even after a clear. Sometimes the program runs away on startup activating every output on and off. Quite a site to see!
My untrained eye thinks the Quad nand gate chip is the trouble. Why? Because there is no resistance between input voltage pin and ground pin.
Is this a logical assumption?

Looking at the chip it is a TC40H000P and also has stamped on it 8416H.
When I lookup the TC40H000P I see this datasheet. But when I look at the Universal schematic I see something different. The upper left gate is not a nand. What is it? An XOR?
Is this some sort of special chip or will a standard TC40H000P work as a replacement? I cannot find any reference to the 8416H.

Well, first off "8416H" is more than likely 16th week of 1984 (Date code)
These usually dont fail. test it with a data scope or data probe.
This circuit looks like a "Follower" and gives a complimentary out put from the NPN transistor driving it.
"RA" and "RB" might be a RESET signal.The circuit is battery backed up.
I doubt this is your RAM problem...

P.S. this is a CMOS device, you wont be able to see any resistance from the input to ground.You MUST test it with a scope or probe!

Kirk

[uniman]

Thanks Kirk. Figured I was not properly dignosing the problem.

You can stop blinking now.