Q*bert Refurb & Repair - Part 4 - High Score Save Fiasco

[@Omega_Mark]

22:12 Famous last words lol.

[@jacklick]

Lol yea perfect timing

[@senilyDeluxe]

Ours has a Gold Cap installed and it saves scores for a few months, but it does occasionally clear them or very rarely overwrite them with garbage. The machine is run at least once a month for 12 hours.

[@jacklick]

I had read about using a super cap instead of nvram or battery. Sounds like it is working well enough for you all.

[@senilyDeluxe]

@@jacklick the clear/overwrite events do not seem to correlate with time past since last power up, so my guess is what you said about power surges corrupting the NVRAM seems to be right.

[@jacklick]

I will definitely be monitoring mine for high score table corruption / loss. You could try increasing the capacitance of C27 to 1000uf and if that doesn't help then increasing C25 to 1000uf as well. That is what the thread on klov mentioned anyway. count me curious

[@classicarcaderepairs4818]

I laughed my ass of @ 22:15 lol. great video!

[@jacklick]

HA! Yea that moment of confidence bit me quick.

[@waynegram8907]

What type of battery lithium what? you mention something about the peak or Spike current being 60mA compared to a coin cell battery being 20mA. The datasheets don't say anything about Spike current, so what is spike current?

[@jacklick]

I meant to say pulse current. It is a Lithium Thionyl Chloride battery. Here is the datasheet. files.batteryjunction.com/frontend/files/xeno/datasheet/XENO-XL-050F-Datasheet.pdf

[@waynegram8907]

@@jacklick I think Q Bert needs 3.6vdc because of the CMOS NVRAM chips? because other arcade games NVRAM for the highscore didn't use CMOS NVRAM. I'm not sure what the Pulse Current does. When you hook up a load to a battery it should supply the current and not supply pulse current.

[@jacklick]

Note: It is CMOS SRAM not NVRAM. NVRAM doesn't require a battery back up and would be a different option that doesn't require a battery. The fact it is CMOS isn't that relevant. I wouldn't doubt all sram from the period is CMOS fabricated. I would assume the load is constant but I mentioned the extra pulse current capability in case it isn't and as another difference to a normal coin cell battery.

[@waynegram8907]

@@jacklick yes arcade games used CMOS SRAM which is more sensitive to the VBatt voltage. The Silicon Diode will DROP move voltage across it compared to a schottky diode. The Datasheets for the SRAM that is used in Q Bert say the minimum is 3.4vdc right? because other arcade games SRAM to save highscore data the used SRAM that only required 3.0vdc? The later arcade games they switches used NVRAM which didn't use a Vbatt.

[@jacklick]

Really? Why was CMOS SRAM more sensitive to Vbatt voltage? You tell me, does the datasheet for the SRAM used in Qbert say minimum of 3.4v?