Last updated: 6 November 2002

ETX-105 RA looseness

Sent:	Monday, November 4, 2002 14:58:49
From: (Al Adrian)
I just bought an ETX-105 and would like to make a couple comments on
what I found regarding excess looseness in the RA axis. Both scopes (I
returned my first one for exchange due to a suddenly jammed DEC axis)
seemed to have excess backlash in the RA axis, even after training and
setting RA percentage to 99%. (about 10 seconds to turn around at speed

I decide to have a look inside the bottom and discovered the cause of
this looseness.  The plastic motor mount assembly was flopping loose on
it's three screws.  I noticed the mount has rubber spacers under it to
keep it somewhat loose, but we are talking 4mm loose here... I eased the
screws down till they started to take up on the rubber spacers and saw
an instant improvement in backlash.  It was better after, with
percentages turned down to 01%, than before at 99%.

When I swung the RA to it's stops  to watch that little cable get
twisted, I discovered why the screws were so loose. They were dragging
their tips on the plate below (above once the scope is turned back
over).  I removed each one and ground down it's end a bit so that I
could have them tight enough, but not let them scrape.

I've found your site extremely helpful.  Thanks a lot.


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