Tapper battery keeps dying. I have the lithium mod

blkdog7

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This is driving me nuts. I have the Bob Roberts lithium battery mod installed in my Tapper. I have installed it correctly and with the diode.

However, the battery only lasts 1-2 days. I keep losing my high-scores. I thought it was Bob's cheap batteries so I bought a new fresher one from Radioshack. Same thing, the battery keeps dying. I have this same kit installed in my Domino Man and it works great. I also had this problem with the Tapper before when I previously had the cordless phone battery. I have this mod in my TRON and it works great. What's going on with Tapper? Why is it killing the batteries?

Could the diode be bad? Anything else?
 
Too much current drain. Could be a bad part in the circuit on the board or you have the wrong RAM chip installed. If you aren't using the low power version of the SRAM chip then it may just be draining the battery on its own.
 
The few times I've ever had this happen....the battery was trying to power the entire 5VDC rail. Something has failed to keep this from happening. Pull the power supply and see if you've got continuity between the battery positive side and the 5VDC line. If you do, that's the case.

Edward
 
the battery was trying to power the entire 5VDC rail.

While the machine is off that is.

Measure the voltage and any of the chips, such as ROMs and whatnot while the machine is off. If voltage IS present, then that's exactly what is happening. The battery should feed the SRAM and nothing else.
Seems to me it's always a bad diode somewhere.
 
The few times I've ever had this happen....the battery was trying to power the entire 5VDC rail. Something has failed to keep this from happening. Pull the power supply and see if you've got continuity between the battery positive side and the 5VDC line. If you do, that's the case.

Edward

+1. I'm thinking that the diode is bad or backwards. I think that theres also a diode on the game board, isnt there??

Matt
 
+1. I'm thinking that the diode is bad or backwards. I think that theres also a diode on the game board, isnt there??

Matt

I'll check the diode on the power supply I installed. Could it be bad from the beginning?
 
I'll check the diode on the power supply I installed. Could it be bad from the beginning?

Yeah, it could be bad out of the box. But, I seem to recall there being one on the board too. You might also want to look there.

Matt
 
Check the diode on the power supply first, then -

on the middle board in the stack - the cpu board. Look for jw3 and jw4. jw4 should be cut and jw3 connected. If both are connected, there's your problem.
Next check the ram at 6b and make sure it is of the low power variety - ie 6116LP If it doesn't have LP after it, there's your problem. If it isn't, there's another ram on the cpu - check and be sure that someone hasn't installed the LP ram in the other ram socket (won't hurt anything, other than to drain your bat).
 
My Domino Man's lithium battery just died. I think it lasted 2 weeks.

What the heck is going on with these kits??

My only MCR game that is still saving high-scores is my Tron and it has a cordless phone battery.
 
My Domino Man's lithium battery just died. I think it lasted 2 weeks.

What the heck is going on with these kits??

My only MCR game that is still saving high-scores is my Tron and it has a cordless phone battery.

Post all the info off the top of the SRAM chip.
 
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