Backup Ram Error MV-1

Hi

My MV-1 is displaying the following Backup Ram Error when I turn all the dipswitches on

Backup Ram Error
Address
00D00000

Write
5555

Read
B240

Does anyone know what this error code means and how it can be fixed?

The backup battery needs replacing, _or_ the backup RAM is dead.

What kernow said!

Most llikely the enable circuitry. That one I dont really knowbecause if it ever showed a B240, I have NEVER been able to fix that particular error.

I have played with the board a bit more and notice that the first time it is powered on READ = B240 the next time READ=B255.

The board will continue to display READ = B255 every time it is turn on after that. Is this because the battery is charging up a little bit?

Also is this a more promising error code?

bump

got a similar one here

2 slot mvs with a backup ram error

Address 00D0000
write 5555
read 0055

battery voltage was at 1.6volts


Any hints ?

I got a one slot with a backup error too

replaced the battery with a 3volt one out of the pc, bodgey yes i know but all i had here

now i get

Address 00D00000
write 5555
read EE55

Looks like one of the rams is bad. Nightmare Tony should know. If you need the rams I do have some extra but when I was looking for some there was a place in Astralia that had them. The og chips are CXK5814 but they are best replaced with TMM2018 and sockets so if they ever go agiany ou can change chips and don't have to solder agian

hmmmm

I have an idea... Welll.... You know I'm working on this unibios for AES.... Well... You see.... Hmmm, how can I put this.... Well.... The AES has no backup RAM so it to also generates backup RAM errors... BUT the next unibios will run on AES hardware... so you know what that means

Raz

The CXK5814s/TMM2018 are *NOT* the backup RAM! Let me explain the 5 types of RAM used on trhe Neo Geo and how to know which is which.

There are 3 banks of 43256 or is it 52256 32K static RAMS, and the pair of TMM@018s., and a pair of 4364 (6264)

1. The Video Sprite RAM is the TMM2018s. On the error screen, they are located at $8000. On a voltage spike, these are the first to go.

2. The final Color Pallete RAM is the 6264 banks. Those help create the second color table for the monitor output (the first color table is located within the 43256 Video RAMs.

3. The Video RAM connected to the main graphics chip is a set of 43256. They contain the text screen space, trhe sprite pattern pointers and the first color pallete table.

4. main CPU RAM is a pair of 43256s conencted to the 68000 and serves as the primary memory, storing the stack and system variables.

5. The work/backup RAM is another pair of 43256s also connected to the 68000 and backed up for power by the battery. Those store saved variables such as cartridge difficulty settings and global settings.


HOW TO TELL WHICH RAMSET IS WHICH?

1. The Video Sprite RAM and the coolor pallete output RAMS are ewasy, being the TMM2018 and 6264 RAMs. This leaves the 6 43256 RAMS.

2. The Video 43256 pair has all the address lines and datat lines connected to the LSPC-A0 or whichever is the main graphics chip.

3. The backup work RAM you can tell as the two of these have pin 24 hooked up to the battery via a routing circuit. All other RAMS are connected to the +5 volt bus. The address and datat pins are connected to the 68000.

4. So this leaves the final main RAM whihc is obvious enough now, connected to the +5 volt bus and to the main 68000.




Hope this helps.

Still available from Ex-Operator

Hi Guys and Gals,
If you need the video rams, I'm selling the orininal Sony chips with sockets (good ones) on ebay. My eBay handle is vidgamman7.
If you are looking for several eMail me. Thanks NightMare Tonyfor the information on the various ram.

w00t!!! B240 problem fixed!

Nightmare Tony said:

Most llikely the enable circuitry. That one I dont really knowbecause if it ever showed a B240, I have NEVER been able to fix that particular error.

Click to expand...

NMT! I'm bumping an old thread with a quick repair note.

Had a 2 slot I fixed for a forum member that worked on the bench but was dead on arrival. It would boot and get to a green screen then flicker off of it and reboot... this was an endless cycle.

Flipped all the dipswitches and received a Backup RAM error, written B240. The dreaded B240 error.

The CS* line (pin 20) on the Backup SRAM was dead. Traces back to the 74HC32, pin 2, were good as were the traces back to the C1815 transistor. All the resistors and diodes checked good. The transistor was OPEN. Infinite resistance between collector and emitter in both directions.

Replaced the C1815 transistor and the board booted right up.

If only I knew this years ago. Thanks again! I always knew it had to do with the enable madness. It was usually some trace corrosion but didn't think transistor there...

Still around, still insanely busy. Keep me in the loop, gang...

This was the first time I've EVER seen a transistor that was open... well, that wasn't blown into pieces. They usually short out!

I guess the corrosion went up the legs and into the body of the transistor.

Nightmare Tony said:

If only I knew this years ago. Thanks again! I always knew it had to do with the enable madness. It was usually some trace corrosion but didn't think transistor there...

Still around, still insanely busy. Keep me in the loop, gang...

Click to expand...

Looks who pops in again, good to hear from you man.

channelmaniac do you ever get tired of fixing these boards because I know I do. I just can't ignore the challenge thats why I still do it I guess.

mainman said:

channelmaniac do you ever get tired of fixing these boards because I know I do. I just can't ignore the challenge thats why I still do it I guess.

Click to expand...

Nope!

I consider it therapy from the day job. There's just something about taking a non working board and making it run again.