Leith,
I couldn't respond yesterday as I was too busy with work.
Tom could be correct, so keep a open mind that it could be some type of filter. Here in USA we have pretty clean power, but Hurco did have line filters on the a/c control side, so you never know what someone's intentions were. Plus you are coming behind someone and I think you said in the past that you couldn't find the tag.
But with what you described, I believe it will be the servo transformer. With two inputs and two outputs it sounds like a single phase transformer. I know there is a way to find out as you can re-wind transformers and seems like you check Ohms, but there is a way to test.
Ok I have figured out some things.....
I was laying in bed and it hit me... yours is probably the same year as mine or it could be a year newer. I am not sure what year Hurco introduced the KMB1, I believe it was 1980 but not sure. I think it only was only around for a short period of time, roughly 1980-1983. It is pretty hard to get info, but there are some guy's out there that know all of this era as they bought during Hurco's Blue phase.
Your machine is simply the manual speed control model, and mine is the programable/automatic speed control model. So with this in mind, I have given you some wrong info. You probably never had the big parajust board in the left cabinet, but a simpler set-up for just getting power to the spindle motor, most likely only a contactor to supply power to motor.
I believe there is another KMB1 schematic out there that is for your machine. I may be completely wrong on all of this, but it hit me that Hurco would not have spent money for the expensive parajust speed control board to just make a contact to the motor when a cheaper magnetic starter would work.
I am assuming your machine is the same year model as mine (1981) and they simply built a smaller head for the manual control, which they ended up implementing the "programmable" speed control in your type of head down the road (around 1984) in the KM3P model. I remember stating a few post back about they added a servo to your model to get the speed control, that actually was the KM3P model, and not on the KMB1m. A lot of things are starting to come back from memory as in the past I had read a lot of things on the internet over the yeas, with some correct, and some not but I realized that I had stated some things wrong. The KM3 is the next generation of our machine with the same smaller manual speed head like yours, but with the twin screen Ultimax control. The KM3P model would be the programmable model for automatic speed control, with the P in the KM3P being "Programmable". There is the chance that yours is just a year or two newer and that model is the morphing between mine and the KM3 style. The original KM1 is much simpler and basically like a Bridgeport mill with servo motors and a stand alone enclosure with the monitor, real basic style, but this was at the beginning of CNC Knee mill for Hurco.
I don't know this part for a fact, as this is my speculation of the KMB1 model number.... K = knee... M = mill... B = b control... 1 = model generation.
I know there was a ATC (Automatic Tool Changer) for the KMB1 as it is stated as a option, but I have never seen one ever with it on there. I have read about 2 machines that had it on them, but one guy said it was clunky to him. I believe it will be the same ATC as was on the MB1, but not sure of that at all. I don't like the look of the MB1, but it is much more rigid as its a bed mill.
Also, I did check my manual and the "Flood Coolant" was a option. So you would have not had 2 contractors, but only 1 for the servo transformer power. Totally my bad for the wrong info in the past, and once again either there is another schematic out there or your machine is a couple of years newer with a different different layout. I still think yours is basically the same year as mine, but without the parajsut board and a simpler left cabinet layout with the right cabinet being practically identical to mine. I saved a lot of schematics over the years and I will dig into what I have and try to get a answer.
In response to your last post, yes you are probably missing the step-down transformer, but when you follow the servo amp wiring you will find out about what is feeding the amps... that will be the fastest way to figure out what they did.
Also, I will still put together a line drawing on what I would do, just haven't had time yet.
Hope this clears up some miss information that I have given about the parajust board, as I believe at this point it did not have it
Will check back later
Robert