Aristocrat of 1983, MPU battery Voltage?

[Jackpot]

Hi, ya all,

I am working on one of those older Aristocrat machines, Micro Processor of around 1983. MPU is located in a cage on lower left of cabinet. MPU board has two Ni Cad batteries in a package + - on one end and + - or the other, batteries soldered together with a tab on each end, inside the package marked Plessey Componets, what is the voltage needed for this board? I can't find it on the batteries or in the manual and I need to replace the battery. Can you use a 3.6 volt ni cad for a Bally E series? What should I replace this with?
Thanks
Rodger
 

[Op-Bell]

It's two standard NiCd cells in series - 1.2V each, 2.4V total. If you can't get them anywhere else, look for replacement cordless phone batteries. These are often 3 cells, but you can remove the plastic sleeve and cut one out. Doesn't even need to be AA in this application, any two NiCd cells will do, any shape and size. They don't have to work hard.

Avoid Nickel-Metal-Hydride cells, as the trickle charge will destroy them in months. Do not, in ANY circumstances, put in a 3V Lithium primary cell. Tempting though this may be, it will reverse charge and you'll end up with an explosion, a fire, or both.

[Jackpot]

Dear Op-Bell

How can I say think you a hundred times without wearing out my fingers? I been here before with these, and always I try to split the batteries so I can see the voltage, but there always glued together with the best glue right were they printed the voltage on each cell, and when I split them the cells the voltage information is lost in the glue slag. Good advice all the way, and every thing I need to know at this time. Thank You again for answering my question!
Sincerely
Rodger Knutson
 

[Op-Bell]

Well thank YOU, I appreciate it, you're welcome. Single NiCd cells are always 1.2 volts, no matter what size or shape they are, it's inherent in the chemistry. On charge they may go up to 1.5v, then sit at 1.3v for a while after, but after a few minutes of use they drop down to 1.2v and stay there until they're discharged, at which point they fall off very sharply. 1v for a NiCd is dead flat, it has no energy left. Just telling you this so you don't take a voltage reading with a meter and think they're the wrong type.

The glue, by the way, is usually hot melt. A hair dryer will often soften it enough to get them apart. It doesn't hurt the batteries to get quite hot, as long as they don't get hot enough to boil the electrolyte or damage the seals. They won't explode, there's a pressure relief seal at the positive end that will blow if they get too hot.

[Jackpot]

You must be part mind reader, you just filled in the missing points I was thinking about. I knew that the 3.6 volt double a size had three cells in the package but I didn't know the why and didn't give it much thought, knowing that these cells no matter what size are all 1.2 volts will be very helpful. Now I won't have to wast time fumbling around the battery questions any longer when I run into it. Do you know if an aristocrat MPU board would run without the memory battery? I can't remember but I thought I was told that a Bally E would run without them, I don't know myself as I have never tried it yet. I am indebted to you, thanks for your time and for feeding my brain with good information!
 

[Op-Bell]

Do you know if an aristocrat MPU board would run without the memory battery?

My knowledge about that is inconclusive. I have one of these machines and it would not run without the battery, but it had other problems that I didn't fix until after the battery so I don't know for sure. I will have to look at the code. I think I remember seeing that if the memory checksum was bad it would correct it, and then sit in a tilt loop until you cycled power. If there was no battery, this would lose the checksum again, so when you power back on it would correct it and then sit in a tilt loop until ... Well, you get the idea.

[Jackpot]

I do, I do, and thank you for all your great information. I'll drop a note if I find that it does, but I kind of doubt it also.
Rodger