There is no video signal on the BNC output connector.
This is used equipment being resurrected, so operational history is unknown.
There is a place on the video card labeled "Q2" that is the right shape & size for a crystal can. The pads look like it was ripped off the board: a short lead soldered in one pad; a hole in the other pad where a lead was soldered (poorly, apparently!). (Rough handling is a distinct possibility: the client is a used-equipment dealer and the fork lift is their main tool...).
The board is populated with 80's technology, mainly 74LS' :: the crystal pads connect to an 'LS04 inverter/driver and then to an 'LS96 parallel-to-serial converter. The 'LS96 spec sheet says that it can be driver up to 25 MHz.
The board uses a 8275 CRT controller, and in the datasheet it says: "CCLK is a multiple of the dot clock and an input to the 8275."
Maybe these clues will tell someone what frequency this crystal needs to be...?
What frequency crystal should I be looking for?
Thanks.