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Title: Need help with schematic and ID of a chip Post by: uniman on April 09, 2010, 03:00:43 AM 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. Title: Re: Need help with schematic and ID of a chip Post by: KirkLasVegas on April 09, 2010, 03:16:23 AM 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 Title: Re: Need help with schematic and ID of a chip Post by: uniman on April 09, 2010, 11:24:21 AM Thanks Kirk. Figured I was not properly dignosing the problem.
You can stop blinking now. :72- |