I have a Yamazen same as the one you bought. Here are the details on my machine in case you find them useful. I cut and pasted them since I had mine for sale. I was wondering what you paid for yours, I sold mine for 5K. The was one on EBAY but I think it sold. Check out the pic.
http://cgi.ebay.com/YAMAZEN-3-AXIS-C...QQcmdZViewItem
YAMAZEN 3 AXIS CNC MILL
Model: 5BVK
Model Year: 1988
Serial Number: 771757
Control Type: ALLEN BRADLEY 8400 MP
TABLE SIZE 42" X 13"
TRAVELS 30" X 15"
MANUAL VARI-SPEED 70-3800 RPM
POWER DRAW BAR
BOX WAYS
40 TP
5 HP 220/3PH.
Machine Manual
Control Manual
Control Schematics
Extra memory.
DNC capable.
AutoLube sytem.
Coolant and mist control.
Tool holders included.
Before you change the controller give it a try. I find it very user friendly and very easy to service and maintain. The machine itself is a good iron and the AB8400 controller reliable. Granted is an old machine- controller. I've had mine for 15 years. The IC's may go bad on you every 5 years but they are easy to replace and cost less than 10 each. If you decide to keep the AB8400 email me
baytool@hotmai.com and I will give you a few pointers to keep it running at its optimum on the cheap. There are a few people that sell spare parts, form P/S to servo amplifiers, to servos in case yours may need any. The most important thing you will want to do is to remove the brushes on the Y-servo and check to see that oil has not soaked them. If it has, dissasemble the servo (carefull with the encoder at the end, but you knew that) clean it up, put it back together, then build a shield with brass or sheet metal on top of the Y-servo to prevent oil form the Y-screw dripping on the servo. After that TUNE all the servos. I can give you the specs or you can get them from the servo amplifier card manufacturer-the name scapes my memory but most machines from that period used the same servo amplifiers so thery are readily available.
More tips later if you want them.
BTW do you know anyone that runs virtual Gibbs on a MAC?