OK, I've finally managed to find an hour in which to do some investigating...
Here's what I have found so far.
The 9pin connector at the edge of the board appears to have 4 'data' lines, and connections for a dual power supply.
The wiring I have found are as follows.
Edge Connector pin 1 - pin 15 of IC2
Edge Connector pin 2 - pin 11 of IC2
Edge Connector pin 3 - pin 5 of IC2
Edge Connector pin 4 - pin 3 of IC2
Edge Connector pins 5 & 6 - Vss
Edge Connector pin 7 - Vdd to all chips, I assume this will probably be a regulated 5v supply.
Edge Connector pins 8 & 9 - this appears to be a power rail fed to the 21 Transistors which gets switched to the rows of leds as controlled by the rest of the circuit.
The Data in & data out of the UCN5821A's appear to be wired like a daisychain, In to out and in to out and in to out etc etc, (In at IC13 out to input of IC12, out of IC12 to input of IC11 and so on.). Also pins 6 are all linked on these UCN5821's and pin 7 are all linked. I assume this is as per the diagram posted by Mike,K8LH
The 21 'row power' transistors are driven by two IC's as follows. MC74HC154 pins 1-11 & 13-17 AND MC74HC138 pins 11-15. each pin via a 680
hm: resistor.
So, The IC's have a seperate power rail. It looks like the LED's also have their own power rail dedicated to them, This power rail is switched to the rows of 60 LED's by a transistor which in turn is controlled by a pin from either the MC74HC154 or the MC74HC138. The colums however appear to be controlled from the UCN5821A's and I assume these chips sink the current which is limited by 1 of 60 x 680
hm: resistors.
IC1, HCF4094BE appears to receive the data from the boards connector and pass this on to the two chips controlling the 'rows' & 'columns'.
I am as yet unsure what the purpose of IC's 2, 3, 4, & 5 are. Has anyone any further suggestions on where I should check next?
Transistors are TIPP116's, Darlington pairs.
hackableFM.