Hi guys,
Colin, the delay won't matter at the moment. I am not connecting the control circuit at all, simply touching wires to various connectors on the ribbon cable that feeds the LEDs. It is a 12 way (4 for digits and 8 for the segments) and the problem occurs still, with NO circuitry connected at all, so it is something in the display for sure.
Roman, as I said to Colin, the problem is not with the control circuit but definately with the LED setup itself. If I connect pos to digit 2 and then neg to segment c then you would expect just segment c only on digit 2 to light. But segment c will light correctly on digit 2 then c on digit 3 may light at about half brightness and c on digit 4 at about quarter brightness, also d on digit 2 will flicker dimly!
The weird thing is that ALL the digits were tested while not joined together and were perfect. They are joined on veroboard each segment being colour coded and all four of the same colour go onto the same strip. Then the digits common anodes are each on a separate strip, making 12 in all which go to a ribbon cable. Then like I said if I touch neg to a segment and pos to any given segment connection the problem begins!
I have actually run a saw blade down the gaps in the veroboard till the white of the board is showing, so none of them are contacting with their neighbouring tracks. I would have thought that it was interference if the controller was running and high frequencies were in play, but this is not the case.
I am at a complete loss as to what could be causing this. I even unsoldered the ribbon cable and tested it for shorts to no avail!
Suggestions please, but remember you can discount the circuitry altogether as I am just testing the bare display with single wires to keep any possible causes to a minimum.
Thanks guys, Al