Re: [CAD_CAM_EDM_DRO] Re: Bridgeport DRO repair?

thefinegunmaker wrote:

>>Does the display box power up? Does it detect motion, but not
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>accurately?
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>
>>Jon
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>The display "numbers" don't light up at all. I took the cover off
>thinking it might be just a fuse, but no luck. The scales don't look
>like the glass variety.
>
>

Well, Bridgeport doesn't actually make any of this stuff, they just relabel
some other maker's product. So, you might do best to examine the circuit
boards and other parts closely, to see if there is any sign of the original
maker's name on it. What type of display is it? The oldest were 7-segment
filament displays, then (Sperry?) Neon plasma discharge displays, then
LEDs and Vacuum Fluorescent displays. You may not know anything
about these things, and I gather you don't have a manual, but if you
can identify the display type, that might be of some help. The plasma
displays (and the ancient Nixie tubes, but those were very rare in DROs)
run on 170 V DC or so, so you don't want to be poking your fingers into
those units. The LED and filament displays generally run on 5 V, and
are pretty tame. The VFDs run on 12 - 24 V, so you are not too likely to
get zapped on those, either.

If you can describe the scales, we might at least be able to figure out what
type of encoder they are. If it is a read head sliding along a hermetically
sealed stainless tube, that is either a Newall Sphereosyn, and magnetically
senses precision steel balls in the tube, or it is a magnetostrictive sensor
(I forget who makes these) that times the propagation of an acoustic
pulse in an inner rod that is affected by the magnets in the slider. You
can tell which because the Newall has no wires connected to the tube,
only the read head. The other has no wires to the head, only the tube.
But, I don't think Bridgeport ever sold either of these systems under their
own label. I think they sold Sony and Accurite scales under their label
at different times. Other linear encoders systems are Farrand Control's
Inductosyn, which uses sinuous metal tracks on a scale and in the read head,
and a decoding/interpolating system identical to that used with resolvers.
Sony, Heidenhain and Renishaw (and probably others) have magnetic
and optical scales using a metal tape that is applied to one machine part,
and a read head that almost touches the tape.

Jon