MVS Backup RAM error-hard to fix?

[Tupin]

I'm looking at a cheap MVS motherboard on eBay, and the auction says it has a backup RAM error. Is fixing this as simple as getting new chips, desoldering the old ones, and soldering in the new ones? Or is there something else?

[madman77]

It depends...it could be the SRAM, or it could be a trace going to the SRAM that is broken or corroded from battery leakage.

[Tupin]

So with the former I just change out the chips it gives me an error on, and with the latter I solder new traces?

Does the motherboard start up without a cartridge, or does it need one to start up?

[channelmaniac]

What's the error message - with the numbers.

That will help me to see if it's a trace problem or a chip problem.

RJ

[cesarwalter]

Hello channelmaniac i have the same error (Backup Ram Error) and I had replaced IC1, U1, Ram3, Ram4 and Xtal but nothing change .
The numbers are:
ADDRESS 00D00604
WRITE 0604
READ 0644
Can you help me? Please!
Thanks !
Cesar

What's the error message - with the numbers.

That will help me to see if it's a trace problem or a chip problem.

RJ

[channelmaniac]

Hello channelmaniac i have the same error (Backup Ram Error) and I had replaced IC1, U1, Ram3, Ram4 and Xtal but nothing change .
The numbers are:
ADDRESS 00D00604
WRITE 0604
READ 0644
Can you help me? Please!
Thanks !
Cesar

Post a pic of the board and point out which chips you replaced.

Also, can you post a close-up pic of the area around the battery?

[cesarwalter]

Ok tomorrow will post some pics !! Thanks

Post a pic of the board and point out which chips you replaced.

Also, can you post a close-up pic of the area around the battery?

[cesarwalter]

I replaced

U1
IC1
Ram3
Ram4
XT
2 transistors (second pic)

Post a pic of the board and point out which chips you replaced.

Also, can you post a close-up pic of the area around the battery?

[channelmaniac]

The data lines for the Backup RAM chips are connected directly to the 68000 CPU. Check for continuity between the RAM and the CPU.

Keep in mind that those are 8 bit SRAM chips and the CPU is 16 bits. One SRAM chip is the lower 8 bits of data and the other is the upper 8.

I think you'll find a broken trace on a data line.

RJ

[cesarwalter]

Ok will check this traces !

The data lines for the Backup RAM chips are connected directly to the 68000 CPU. Check for continuity between the RAM and the CPU.

Keep in mind that those are 8 bit SRAM chips and the CPU is 16 bits. One SRAM chip is the lower 8 bits of data and the other is the upper 8.

I think you'll find a broken trace on a data line.

RJ