Rock-Ola LED Display Issue

I have a Rock-Ola 490 and the LED Display has segments which don't light-up (on all 8 digits). Is this likely to be a fault with the digit units themselves, or could the fault be elsewhere?

I am guessing the digits themselves are faulty, but don't know how to test them, or where to get replacements?

Any help would be appreciated.

Keith,
Got Service Manual---schematic ?
This should tell you, what voltage the LED's use, the "common" pin and which pin for which segments.
If one is not lighting, compare it to a lit segment--no power ? It's a bad driver. Power, it's a bad LED.
LED cases are usually marked with a name, and or, at least a number. If needed, take that to your local "Radio Shack" and axk questions--they say, (or at least, used too) they "have answers"( ) Ron Rich

Thanks Ron,

You are quite right (as usual), the digits are marked, MAN6780, which I found on-line.

From the voltages at the pins (as per the schematic) I would have to say that the LEDs are faulty. When an LED is not lit, when it should be, the voltage is like 8v !!! - Only supposed to be 2v. One digit that isn't working at all is reading 12v.

Voltage is definitely there, but going very high when an LED isn't working.

Keith,
Glad you found it--let us know the outcome, when you get the new LED's.
Ron Rich

Ron,

Got the new LED digits today and installed them. Everything is great now, except for one which is not lighting at all. I knew about this fault before, but I wanted to get the new LEDs in before looking at it. I know the fault isn't on the PCB where the LEDs are mounted and I know the ribbon cable is okay, which means it must be somewhere on the "back" board of the System 2 Control Unit.

I will have to have another look at the schematic, but now I am unsure what to look for. Any ideas?

Keith,
Is the failure in one "enclosure", or just one of the segments in one enclosure ?
Ron Rich

Ron, it was a full enclosure, but I found the culprit. The ULN 2803A IC is faulty - ordering a new one today.

Keith,
Cool--glad you found it--driver chip ??
Ron Rich

Yes, the driver chip... and just thinking about our conversation in the "Wanted" forum, regarding the cost of a Rock-Ola Reject Button, this 18-leg IC cost .93 cent, and that wasn't from a "cheap" place.