Re: I need some help retrofitting modern controls on a Bridgeport Series II Mill

Sounds very similar to my series II setup. My electronics were
inspected in 1976, so they can't be that different.

I yanked the spindle wizard and put an aftermarket b-port handle on
the quill. I used www.GeckoDrive.com G202 drives, and PMDX's new
breakout board. Their power supply filter/charge dump board would
have saved me a bunch of time, but I built my own power supply anyway.
I forget exactly what voltage I used. Somewhere near 65V. It was an
e-bay tolroid transformer and I played with the windings until I got
that voltage. I used some of the lower voltage secondary windings to
buck or boost the primary. I forget what value caps I used, but a
local surplus store had some 100,000 uF or so 25V caps (new) on
clearance. I hooked them in series with something like 240 Ohm
ballast resistors. This got each cap's voltage within 0.1V. The
transformer was something like 850VA, which seems more than enough. I
have not measured max current draw (yet), but I was surprised how
little the voltage sagged when jogging all axis.

I don't remember exactly how fast I'm moving. I'm not sure I got it
all set up properly yet. I think some of my oil passages blocked. I
don't use the air assist on the knee (yet), 'cause when I do,
sometimes the knee binds on the way down. I think I'm running the x
and y close to 50 ipm and the knee at 15 ipm. I can at least double
the Z rate with air assist, but every now and then it binds on the way
down. I run my geckos at 7 amps.

Fist thing I would do is replace all the wiring between the steppers
and your new control box. Same with the limit switch wiring. Mine
was _very_ brittle. One of the fastest ways to kill a gecko drive is
to disconnect or short the motor windings under load. Took me about
an hour and I think it was money well spent. You might also want to
verify the motors are good before going too far. Make sure there are
no shorts (between windings or to the case!) or the motors have been
"demagnetized". I hear a common failure mode of the old drive
electronics is a shorted transistor, which can quite often over
current the stepper motor before a fuse blows.

Email me off list. I've been (slowly) scanning in my manual. I plan
on eventually posting it to the B-port manuals list, but before then,
I'm going to include it with my auctions when I eventually get around
to selling my old b-port parts.

Sorry for rambling and disconnected thoughts. Gotta get to my day job...

- Steven Ciciora

P.S. I have heard that Mach2 has a mode where the printer port can
"phase drive" the original electronics on the b-port. But to me, it
wasn't worth the hassle. I think the geckos way outperform the
original electronics. Just an option if you have (a lot) more time
than money...

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "oldpayphones" <larry@3...> wrote:
>
> Hello,
> I am new to this group and have read some of the old threads regarding
> retrofitting a windows based controller and re-using the steppers and
> one of the power supplies. Alas I am still clueless and need some
> guidance.
> The machine is a 1975 BP Series II NC with a seperate BTR (tape)
> cabinet and as far as I can tell the steppers are NEMA43 12A with
> about 600 on the holding torque (please correct me if i am wrong). I
> was wondering what drive would be suitable for them. I presume the
> gecko's are too small looking just at the amperage, or maybe they
> would be ok at the unregulated 56V from the original power supply. I
> read about someone building a regulator and re-winding a transformer
> for higher voltage??? I would appreciate any help as to how to do this
> and what the advantages and disadvantages are.
>
> Thanks in advance,
> larry@3...
>