Got the manuals, but... Found the problem. Nice burn spot on the main board. Around one of the analog connections to the servo drive for one of the axis's are some burned up components. Only thing i can think of is something happened in the servo drive and high current got into the main board. The board was even burned on the back side!
So I have three routes to repair it. The control is toast and even if I did repair I would still have a 23 year old control. First, I can keep the original servos and drive them with something like the Gecko 320 servo drives and and install encoders on them for feedback. This would be the most expensive route. Somewhat time consuming as I need to pull the bed off to run new encoder wires. Also the resolver in the head would have to be replaced.
Second, I found Analog Devices makes an IC that drives a resolver and outputs position info in serial, parallel, and quadrature with an index pulse at 1024 counts per rev. Accuracy is 11 arc minutes. Plenty good for this. The IC's are around $18 for two. The circuit is real simple to just get the ABZ signals out of it. It is a 44 pin LQFP so I will have to have a board made to do the two axis plus the spindle. Again I would use geckos or an equivalent brush type servo drives.
Last is I have two 200 watt SimpleServo Ac Brushless Servo motors with brakes and drives. About the same physical size as the original motors. The drives have Step/Dir inputs so I can hook up to any generic parallel port with little issue. Since I have the motors and drives this would be the cheapest but most time consuming as I need to modify brackets and bore the drive pulleys. Also have to pull the bed to run the new wires.
Tough decision. Leaning towards the second option. I think I can use the original front panel. The opening is 7" for the display so I might be able to find a small LCD to go in its place. Most of the buttons and MPG can be reused I think. May end up going with something like the homann designs ModIO board:
Here are a couple better pics: