[amsat-bb] Re: G5500 Elevation Rotator Short Circuit?

Tim Cunningham tim_cunningham at charter.net
Fri Oct 7 10:50:50 PDT 2011

The common failure of the motor windings is caused by heat which causes the enamel coated wire to breakdown. When the enamel breaks down an inner winding short results.

I have successfully rewound motor windings on these rotators just to say it could be done, but it takes some work (not recommended).

I have never seen one of these motors with an open winding. The failure mode on the 8 that I have repaired were always enamel insulation breakdown as a result of overheating.

Tim - N8DEU

Sent from my HTC Tilt™ 2, a Windows® Mobile phone

-----Original Message-----
From: Clive Wallis <amsat-bb at g3cwv.co.uk>
Sent: Friday, October 07, 2011 11:35 AM
To: amsat <amsat-bb at amsat.org>
Subject: [amsat-bb] G5500 Elevation Rotator Short Circuit?

I wonder if this is a known fault.  Recently the fuse on my G5500 
blew.   The problem seems to be a short on one of the motor circuits.

Checking the DC resistance at the control end, the resistance of one 
winding is 1.2 ohms, whereas all the other windings are 4.6 ohms.

I could understand a motor burning out and going open circuit,  but a 
short circuit seems less likely.  I'm wondering if it could be a short 
on the cable at the rotator end, where it is subject to much bending.  
There's about 15 metres of cable.

Any thoughts would be much appreciated.  Unfortunately, at the present 
time I'm not able to inspect the rotator.  It's stuck in the horizontal 
position, so I will still be able to use the antenna for low elevation 

73     Clive     G3CWV

Hitchin, North Hertfordshire, UK
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