MAD PLANETS NVRAM MOD - Which chips? What else?

blkdog7

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I need to get the battery off of my Mad Planets PCB. What CMOS RAM do I need to replace with NVRAM? Anything else to do? I googled the hell out of this and couldn't find anything.
 
Please excuse my ignorance.. But doesnt Mad Planets share the same or similar qbert CPU pcb? Couldn't you just install one that works for a qbert? As I know that mod is quite documented.
 
Definitely similar and I believe it's the same, but I'm ignorant as well. I wanted to get confirmation before I pulled out the snips.
 
MK48Z02 or DS1220. I dont know the simtek part number off the top of my head. I believe two of the rams need to be replaced, its the two on the right looking at the pcb with the edge connector facing north.
You should have 6116LP in there (low power rams, battery backed).
 
Yep, (2) 6116 ram.. Just like qbert.. Ah, so I'm not crazy :)

MK48Z02 or DS1220. I dont know the simtek part number off the top of my head. I believe two of the rams need to be replaced, its the two on the right looking at the pcb with the edge connector facing north.
You should have 6116LP in there (low power rams, battery backed).
 
I did this mod to my qbert, but having issues where in mid play it will just reset (and wipe all high scores) (yes, 5v is dead on no issues), switching back to 6116 and a battery, as need to be original for a special event in july anyways :p
 
(yes, 5v is dead on no issues)

This might be your problem if your measuring voltage at the power supply. Qbert has significant drop in voltage across the harness and the nvrams are sensitive to voltage. If it drops slightly below 5v it locks the ram out. Ideal voltage at the nvram would be around 5.05-5.10v.
 
This might be your problem if your measuring voltage at the power supply. Qbert has significant drop in voltage across the harness and the nvrams are sensitive to voltage. If it drops slightly below 5v it locks the ram out. Ideal voltage at the nvram would be around 5.05-5.10v.

i will bump it up a litte, its 5v on the game pcb, but i will check at the nvram & cpu.
 
replace C5 & C6 with Simtek STK25C48 RAM
Also added a jumper at D3 as pictured.
ImageUploadedByTapatalk1365101590.804452.jpg

I also upgraded the capacitor at C25 to a 470uf 35v to lengthen the reset delay. Have had no problems with my high scores resetting since.
 
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