chinese dro scale shorting dro display?

hi all-

i've run into an interesting problem with the chinese dro scales/displays:

i recently mounted a dro scale to a 8x12 lathe. initially the display
itself (a cheap shars unit) seemed to work fine, then it just all of a
sudden went dim. after checking connections, cables, cleaning the scale,
etc.. it appears that the problem is an electrical one. i found
this out by disconnecting one part of the scale where the display unit is
mounted to the saddle and noticing a very small spark from the tip of the
screw as i touch it to the hole in the saddle.

if i unplug any part of the chain, the display unit lights back up to
normal. the moment the lathe or any part of the display > cable > dro
scale is connected to power simultaneously the display dims again.

i'll be checking with a voltmeter today to see if i'm shorting or what,
but can you see what's going on here?

the blog entry which describes this somewhat:
<http://www.fignoggle.com/workshop/item/2006/8/2/8x12-cnc-project-installing-dro-scales>

the actual picture. note that the scale display unit is not connected to
the saddle.
<http://www.fignoggle.com/workshop/media/8x12/figNoggle_8x12DROZ.jpg>

thanks for your help!

david


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