In article ,
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The 12" scale for my Acu-Rite III just won't work. It's an older mini style
scale 1" high by 3/4" deep. It has the round connector on the end with pins
lettered A thru F.

I took the scale and read head apart down to the board in the head.
Emitters and detectors seem to be working but the chip just won't fire on
one of the outputs. Acu-Rite says it's a proprietary chip from 1983, which
explains why it has no markings on it.

(Thanks to Ned Simon for the disassembly advise - it went very smoothly).

If anyone has a read head from a dead scale, or even a dead read head they
can part with please contact me, (maybe I can make one good one from two bad
ones).


They show up pretty regularly on ebay, both complete scales
and reader heads. I recently bought a new old stock head
for $115 vs. $260 from Acurite. This is the search string I
used for a saved search which seemed to catch most relevant
stuff and not a lot of garbage:

(acu-rite,acurite) +(dro,scale,encoder,read,reader) -
thermometer

I expect the circuit in the head is essentially a pair of
comparators that square up the analog signals from the
detectors. Why not make up your own black box to go outside
the read head while waiting to find a replacement?

Ned Simmons