Has anyone tried to hook up to a Daktronics clock you find at most American High School Football field/track. I think they call it: "All Sport 3000" A control box about 6" x 16"

yes. normally the older style (incandescent bulbs) use the All Sport 4000 controller and the newer ones (LED) use an All Sport 5000 controller (not sure if the 5000 is backward compatible)
The All Sport 4000 controllers will need to use a modified data cable that connects to the back of the controller and pig tails out to the scoreboard jack and to a Lynx serial port. The Lynx data jack is usually what needs to be added (i have the pin outs if needed)

If you have a "regular" on board serial port or an ethernet to serial port you can use the Allsport.lss script in Lynx for the All Sport 4000 controller.
If you are using a usb to serial converter and / or are using the ALL Sport 5000 controller you will need to use the newly added Powertime.lss script. This will allow use of a usb to serial converter.
The All Sport 4000 controllers used real screwy serial protocols that could cause Lynx to hang when using a usb serial converter.

Thanks for the reply.

It is an Allsport 5000.

I hooked up through the 24 pin port with a port adapter (Radio Shack) 24 pin to serial port, Null modem cable to my serial to usb adapter..Money..

Did not get to configure all the options that may go with it but was able to get stop watch function with the lynx synched.

Worked great