Re: DRO intermitent fails

Sven

Guten Morgen

>   From: Jon Elson <elson@...>
>
>Sven Peter wrote:
>
>> Aligning the Mitsubishi-DRO-ruler I over traveled it.
>> First I got no readouts. After opening it and cleaning the ruler with
>> contact cleaner it worked only in the test by hand.
>> Later I had to readjust the spring and then it started to work
>> in one direction but sometimes in the other direction it fails to
>> count the travel. I suspect that there is still some oil on the
>> glass ruler or the reader doesn't travel right.
>> The amazing thing is that the readings do not fail on the same spot
>> and not always and  there is an area of 25 cm where the ruler works
>> perfect.

<s>>

>Also, if the analyzer grating is allowed to twist, instead of sliding
>straight parallel to the scale, it will throw off the quadrature
>90 degree relationship between the A and B signals.
>
>The tricks to get the wire, bail, link or whatever that drives the read
>head back and forth without bowing (which effectively causes
>backlash) are many, and these usually take the brunt of overtravel
>accidents.  When messed up, they can cause all sorts of alignment
>errors between the analyzer and scale gratings.

I've seen symptoms just like these from one where the read head is rotated
a little off axis from the scale. Cleaning helps because you'll get more
light to the pickup. So it's is natural to think that that is the whole
problem but if the reader hit something during the overtravel it will also
be rotated out of allignment. Find the screws that hold the head and
imagine which direction the holder would rotate if pushed. You should be
able to tell which way it was rotated. Loosen one screw and push back
just a bit. Keep trying small moves.

I doubt anything serious is wrong, like the grating being broken loose or
it wouldn't work at all. I just sent one head out for repair and it was
about $100.

Ray