One axis on my grinder readout is reading erratically and the symptoms
point to the pulse detection/shaping circuit being out of alignment.
The scale indicates approximately the proper distance travelled, but
only counts in one direction. In other words, move forward 1 inch and
the readout will indicate approximately 1.0000; move back to the
original position and instead of returning to 0.0000 it reads, more or
less, 2.0000.

I've swapped scales and the problem follows the scale, not the readout
channel.

The scales are Sony p/n SR-2711 and the readout is an LF-200. I
believe they date from around 1985.

I've fixed similar problems in optical encoders, but this is a
Magnescale and most of the circuitry is encapsulated in what appear to
be three mini circuit boards - the long brown devices in the photo. I
haven't been able to make an informed guess as to the function of the
several pots. The optical encoders I've fussed with have one pot for
each channel that tweaks the switching point of a comparator; this is
clearly more complicated.

http://www.suscom-maine.net/~nsimmon...caleHead01.jpg

Before I hook this up to a scope and start fiddling with the pots,
does anyone have or know of an aligment procedure for this unit or any
similar?

--
Ned Simmons