HS Save Kits Losing High Scores?

[elfyhead]

I first just bought nvram and jumpered the diode. It worked for about a month then didn't save anymore. So I just bought an arcade shop kit -- did the capacitor, diode new NVRAM -- still about every 2 week the thing resets...

I took the game to work and everyone bitches the high scroces get wiped....

so I basically bought that damn nvrams twice for nothing....

Maybe someone will make a different kit or has some new ideas. I think its the game I think its corrupts the ram

this is roughly the same problem i have. every couple of weeks (sometimes more often) it resets the scores on startup (could be on shutdown, since there's no way to distinguish of course).

the 3 types of NVRAM i've tried are the STMicro M48Z02-70PC1, Dallas DS1220AD-100ND+ and Dallas DS1220AD-150+ (so a 70 ns, 4.75V; a 100 ns, 4.5V; and a 150 ns, 4.5V). i'm worried/wondering about the conditioning on the input power because the STMicro is a 4.75V, and the two Dallas' are 4.5V, and i've run across some mention that on q*berts you might need RAM that goes all the way down to 4.25V for Vcc.

 

[JoeB1355]

switcher

this is roughly the same problem i have. every couple of weeks (sometimes more often) it resets the scores on startup (could be on shutdown, since there's no way to distinguish of course).

the 3 types of NVRAM i've tried are the STMicro M48Z02-70PC1, Dallas DS1220AD-100ND+ and Dallas DS1220AD-150+ (so a 70 ns, 4.75V; a 100 ns, 4.5V; and a 150 ns, 4.5V). i'm worried/wondering about the conditioning on the input power because the STMicro is a 4.75V, and the two Dallas' are 4.5V, and i've run across some mention that on q*berts you might need RAM that goes all the way down to 4.25V for Vcc.

Last go-around I used swapped the ps for a switcher and the Arcade shop adapter. Qbert runs fine with and I hoped might fix the high score trouble -- but alas it still resets every couple weeks

 

[mrbill08]

C25 is the power on reset cap. I've had to go as high as 1000uF on one board to make the high score save stable.

C27 is the Vbatt cap - I use 1000uF with a lithium battery and the low power SRAMs. Since you are using an NVRAM, it may not matter but would not hurt to try. I have not investigated but there may be something funny with the +5V rail during power up or power down and this larger cap may help.

One last thing that is worth a try - that B6 (74HC138) likes to get flakey and fail and it controls the chip selects for the NVRAMs. If you have a mind to, you can try replacing it - note that it is connected to C27 so again trying that larger cap (1000uF) may help.

If you can, add one mod at a time then retest instead of doing all of them at once so maybe you can identify which fix did the trick.

Good Luck and please report any positive results,

Bill

NVRAM. bought the kit from arcadeshop. after i ran into the problem i tried two other 16k NVRAMs (mainly different speeds), but that didn't make a difference.

i jumpered diode D2, and replaced C25 with a 470 uF, but i don't think i changed another capacitor - did i miss one?

 

[elfyhead]

C25 is the power on reset cap. I've had to go as high as 1000uF on one board to make the high score save stable.

C27 is the Vbatt cap - I use 1000uF with a lithium battery and the low power SRAMs. Since you are using an NVRAM, it may not matter but would not hurt to try. I have not investigated but there may be something funny with the +5V rail during power up or power down and this larger cap may help.

One last thing that is worth a try - that B6 (74HC138) likes to get flakey and fail and it controls the chip selects for the NVRAMs. If you have a mind to, you can try replacing it - note that it is connected to C27 so again trying that larger cap (1000uF) may help.

If you can, add one mod at a time then retest instead of doing all of them at once so maybe you can identify which fix did the trick.

Good Luck and please report any positive results,

Bill

thanks much. i'll try those soon, but for now i've got bigger problems (http://forums.arcade-museum.com/showthread.php?t=170303)!