carlos martin wrote in message
...
Hello,

I have an old (80s I guess) moving led display. It has 3 boards full
of leds and is programmed via a keyboard that connects via serial db9.

Upon startup it would only show squares moving sideways. I replaced
some small battery (3 button batteries stuck together) and then it
would show some letters from other alphabets (accents and circles and
what not), but mostly squares again.

It doesn't respond to any command from the keyboard.

The mainboard has three chips which I guess are processor, ROM and
RAM:

D8049HC 195
MBM2764-25
TC5517APL

I am about to replace the three of them, but I guess I would need to
find the original ROM to program this.

Can anybody help with this? Can the fault be with the processor or the
RAM and not in the ROM?

I didn't find any make and model on the device but I can provide more
information on request.

Thanks in advance



If the main chips are socketed and sprung clip type, probably
grime/corrossion , note orientations, clean/joggle the pins and reinsert ,
perhaps with a turned pin socket between IC and the original, if not
prepared to remove the original sockets.