Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Help fixing moving led sign

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
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Default Help fixing moving led sign

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.


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Default 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
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Default Help fixing moving led sign

On 6/15/2012 2:32 AM, carlos martin wrote:
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


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.
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Default Help fixing moving led sign

carlos martin wrote:
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?


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.




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Default Help fixing moving led sign

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

I have an old (80s I guess) moving led display.


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

It has 3 boards full
of leds and is programmed via a keyboard that connects via serial db9.


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

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.


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

http://www.soemtron.org/downloads/di...s/tc5517ap.pdf

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.

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


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

D8049HC 195
MBM2764-25
TC5517APL


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

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
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Default Help fixing moving led sign


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


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?


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Default Help fixing moving led sign

carlos martin wrote:
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


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

https://en.wikipedia.org/wiki/Intel_MCS-48

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 :-#)#

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Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
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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.


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.
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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,


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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 one seems to be cheaper, so I am tempted to go that way.

http://www.ebay.com/sch/i.html?_trks... mer&_sacat=0

http://www.aliexpress.com/wholesale?...d=0&manu al=y

Cheers,
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