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Subject: Re: 1812 caused RA motor to go bezerk
From: Bill Arnett
Reply To: mapug@shore.net
Date: Sat Aug 31 00:33:59 1996

At 11:21 PM 8/30/96, Mark & Cheryl Buettemeier wrote:
>I recently purchased an 1812 voltage converter for use with my 8" LX200. Now
>let me preface this by saying that the scope is relatively new, about six
>months old, and up until now I haven't had a stitch of trouble with it.
>
>My first attempt to use the 1812 converter on my scope resulted in the RA
>motor to immediately go bezerk upon power-up. The hand controller and DEC
>motor both go through the normal power-up sequence and then seem to work fine.
> All the while, the RA motor is continuously jerking around at various speeds
>in a fashion I can only explain as spastic. Now, regardless of power supply,
>the scope always performs as I've described with I power it up. Feels to me
>like the 1812 blew something in the scope...

I'm no expert, but I would guess that the Hall effect sensor on the RA worm
is kaput. If so, you'll have to replace the whole RA motor assembly. But
that should be covered under warranty. And its an easy job.

But why did this happen? Try checking the output of the 1812 converter.
When I destroyed mine the output was 12v instead of 18v. If so then it is
blown, too, probably the LT1170. Open the 1812 converter up and see if
anything looks like its fried. Its possible to fix the converter, too, if
you can really verify what's wrong. The LT1170 is a hard thing to find but
I managed to get one from DigiKey.

Good luck. (You might also check the mapug archives. There was some
discussion of this last March.)

---
Bill Arnett                 "Science is a way of trying
San Jose, CA  USA            not to fool yourself."      -- Feynman
billa@zNet.com                              <URL:http://www.seds.org/billa/>