1. I sold some parts of this Bridgeport CNC mill, specifically the
Heidenhain controller and an optional keypad for same. After
subtracting the sold price from the price I paid for the whole mill,
the cost of the mill dropped down to $133.

2. I spent about an hour yesterday looking into the control cabinet,
the one with wires and relays, not the one housing the CNC computer. I
have gotten to the point of better understanding of some aspects of
wiring.

I was first glad to note that my phase converter is relatively
balanced and outputs 235 and 246 volts depending on legs.

There is a strange relay that powers up the main transformer, that was
not obvious to figure out, so I had to push the contacts of it with a
screwdriver.

I found, specifically:

a) The main transformer is shaped like digit 8 and seems to take
single phase only. It is labeled as 3 kVa. I am very tentative on
declaring this a 1 phase transformer, but this is what it looks like,
as I found only two inputs with voltage of 235 volts between them.
The transformer seems to output several voltages, but one of them is
380 volts.

b) The servo drives are Bosch Z15-1-240v. Despite "240v", the drives
are connected to the transformer's 380v output. I searched Google on
this and found a lot of desperate people looking for schematic, no
schematic, and a lot of web spammers advertising "repair" of these
drives.

c) The drives seem to have 380v as power in, have control inputs from
the controller setting speed, and what seems to be tachometer
input. (as I said yesterday, the motors definitely have tachometers on
them).

d) There is three more wire coming out of the servo drives, that seem
like they would probably be used to drive motors. I am not sure why
three and I am not sure whether I can figure it out reliably (thoigh
maybe I can).

Therefore, I have two choices:

Choice #1: just sell those Bosch drives, which seem like they could
fetch some reasonable amount of $$$ like $300, and follow the original
advice of Karl and install the AMC drives that I purchased on Karl's
recommendation. I will try to test the AMC drives prior to removing
Bosch drives.

Choice #2: Leave Bosch drives plugged in, leave their connection to
servos as is, and hook them up to Jon's PPMC. The attraction of choice
#2 is that it is superficially easier. However, I do not see the
inhibit function on the drives that could be triggered by limit
switches, and thus I think that they are not as safe to use. I would
have to program inhibit functionality in software, which is obviously
less idiot proof than having drives that are unable to overrun the
limit switches. Also, I believe that I may need three phase to run the
mill, which is something that I hope to avoid.

I will sit on it for a couple of days.

My plan for this weekend is to figure out the power wiring of the
servos. (what goes into the power connection box, how everything is
connected and numbered). Also to reinstall the mill's head.

i