MV-6F...Backup ram faults...??.

Hello guys...any help here would be greatly appreciated!!...Thanks!.. .
Well my 6-slot has just developed an unusual fault..it came on after 1-week of me replacing the backup battery...
I replaced it with an 3.6v 160MAH battery.... all was well & saving scores etc.
Then last week i got this message when i switched it on!!-
'Backup ram error'
address write read
00d00000 5555 55FF
Btw...that above warning message is very dimly lit on the monitor..i tried my 4-slot in the cab...all was ok..checked voltages & all is fine.
Stripped the pcb down many times & cleaned & checked for any cold joints etc..also removed the battery...still the same!?.
Any ideas? thanks guys.

Bad chip or a few cut traces.

Not too hard to replace the chip if you have the right soldering gear.

The data pins on the chip should map over to the data pins on the BIOS chip. There are 2 of those SRAM chips... each are 8 bits wide. The BIOS chip is 16 bits wide. Make sure that one of the SRAM chips data pins has continuity to the lower 8 data bits on the BIOS chip and the other as continuity to the upper 8 data bits.

If you find screwed up traces then you need to fix 'em. If you don't, try replacing the bad chip. A logic probe can help you determine which one is bad by checking the signals on the data pins.

Make sure you use a digital voltmeter when doing the continuity checks. Some of the analog ones have 9v batteries in them and will cause harm to digital circuits that run off of 5v supplies.

I sent you a PM for your email address. I have the chip datasheets for the sram and a compatible EPROM for the BIOS chip. That way you know which pins should connect for continuity.

Raymond

Many many thanks for your help raymond..i'll send my mail id now..
Cheers!!!

They are on the way to ya.

Good luck!

Raymond

hey guys,

I'm looking at a machine that also has an error code that comes up on the screen. The person selling it says it turns on, the moniter displays the game for a little bit, the speakers make some crackle or tone and then "ERROR 080" comes up on the screen.

its a 2 slot woodgrain cab. Anyone know what the error means? how hard it it to repair?


Thanks!

-Luke

Strange...

Typically that is a "Z80" error and means there some generic issue with the sound subsystem on the board...

It could be: bad Z80 CPU, bad sound RAM, bad sound ROM, bad Yamaha sound chip, or a bad chip that interfaces it to the Neo Geo chipset/circuitry.

Start with replacing the 6116 SRAM and then replace the Z80.

Be careful to NOT pull any board traces up or any plated through holes out or you'll screw up the board. If you do that you'll have to patch it with little bitty wires.

RJ

its entirely possible that its Z80. I havent seen the machine, just going by what the guy selling it said on the phone.

Whats the general cost of those parts? How hard are they to find/install? I'm an auto mechanic and theater technician, so I have some electronics expierence but i'm no pro.

Is there any way to bypass the problems to make the machine run for furthur testing?


Thanks again for the quick reply!

I can sell ya the parts but you need to be good at desoldering or you'll damage the board.

I could also replace those chips for you for a nominal cost... if you want to do that just PM me.

RJ