Help fixing moving led sign

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.

aye, did that already, some of the pins have turned witeish, couldn't remove that white stain

that turned pin socket is a very good idea, i think i'm going to head that way before spending 30$ on chips

thanks a bunch

I had a similar sign. the DB9 was NOT RS232. Was some kind of scan-code thing. Had to reverse-engineer the interface to make it work.

is it from cybernetic data products?

check the power supply, or run it from a bench supply. those signs can be be fussier than you might expect.

On Fri, 15 Jun 2012 02:32:18 -0700 (PDT), carlos martin put finger to keyboard and composed:

Look for YWW or YYWW (Year/Week) date codes on the ICs. That should tell you when the device was manufactured.

Are the voltage levels +/-12V or similar? If not, then I would suspect something other than RS232.

The batteries appear to provide backup power for the TC5517APL static RAM. In standby mode the SRAM draws 1uA.

By removing and replacing the battery, you would have changed the contents of SRAM. That's where the display data would be stored. This would suggest that the microcontroller and its SRAM and EPROM are OK, at least partially. In fact, it could simply be that the SRAM has lost its stored message, in which case you would need to reprogram the display.

I would remove the microcontroller (uPD8049) and observe whether the display still moves. If the display stops, then this would confirm that the microcontroller is required to move the display.

The microcontroller has 2K x 8 of on-chip ROM. I would think that this would be enough memory to store a simple moving display program. I suspect that the external EPROM would store the bitmaps for each character. It might be interesting to note whether the display changes when you lift one or more of the EPROM's data or address pins. If the display continues to move after you do this, albeit with distorted characters, then this would suggest that the EPROM does not contain any program code.

It could also be that the EPROM has a checksum which is verified by the microcontroller at power-on. It might be worth reading the EPROM several times in a device programmer to check whether the data are consistent.

I'm betting that you just need to reprogram the display, thereby restoring the SRAM's contents.

- Franc Zabkar

Do you know its history, ie the keyboard did work. Or has someone sold it with some cobbled-together kbd for a quick sale?

I used to own a IGG moving sign with a non-standard serial link to keyboard. That company in the 80s suddenly found that Chinese made moving signs were coming into the country for the price that IGG had to pay for just the LEDs in their signs, so goodnight IGG

Does it have DIP switches for baud rate setting?

The 8049 is a pre-programmed CPU, unless you have the code you are SOL on that.

The 2764 is an Eprom (if it has a paper/foil label over the window) and can be read to see if it is still good (several reads the same, probably good), unless the data is FF or gibberish with relation to coding that the 8049 needs (you need to understand a bit of assembly language to figure that out) or it could be the alpha-numeric look-up table.

TC5517 is the Static RAM - where your messages are stored. It is likely to be scrambled and needs to be cleared. Perhaps that was a keyboard command.

If you can find the manufacturers name for the moving sign that would help a lot...

I have one of these tucked away in a corner of my shop, haven't looked at in in a couple of decades, mine did not have battery backup though (AIR), I may have the manual for it packed in the same box. If so, I'll scan and upload somewhere and post the link here.

John :-#)#

You might have a point there, the power supply is pretty knackered, but as it powers On OK I didn't make it a suspect...

Don't know about the brand, didn't see any disctintive logo or identification, will check further.

Thanks for all the help guys...cunning stuff.

I will try the different ideas you've given me so far and come back with results.

Will also buy one of them eprom programmers, for 50$ a lot of fun can be had.

Regards,

By the way,

Which eprom burner would you recommend me to buy? I see basically two types= : a simpler USB one with just one slot or a more complex (parallel and usb)= with a lot of slots (even for DDR ram). Funny thing is that the complex on= e seems to be cheaper, so I am tempted to go that way.

Cheers,