[amsat-bb] Re: G-5500 Troubleshooting

i8cvs domenico.i8cvs at tin.it
Sun May 2 15:30:11 PDT 2010

  ----- Original Message ----- 
  From: John Meeks 
  To: i8cvs 
  Sent: Sunday, May 02, 2010 11:17 PM
  Subject: Re: [amsat-bb] G-5500 Troubleshooting

  i8cvs wrote: 
----- Original Message ----- 
From: "John Meeks" <jmeek at gaslightmedia.com>
To: <amsat-bb at amsat.org>
Sent: Saturday, May 01, 2010 11:22 PM
Subject: [amsat-bb] G-5500 Troubleshooting

One more thing... Given that the cable tested OK, what does the open 
reading from 6 to 4 suggest? My reading of the schematic diagram is 
sketchy at best.

Any and all help will be greatly appreciated.

John Meeks

Hi John, KC8ZFN

After the carefull troubleshooting you did and described the actual open
reading from 6 to 4 in the az. motor suggests two possible autcomes.

1 ) The limit switch SW6 inside the rotator is defective and is an open

2)  The winding of the motor connected to limit switch SW6 is open
      so that the motor cannot run nor left and nor right

Since 6 and 4 are an open circuit the electrolitic unpolarized capacitor
inside the motor appears to be not involved in this type of problem.

Please let me know just for curiosity the result of your investigation
but I believe that you have to open the azimuth rotator.

Best 73" de

i8CVS Domenico

  Thanks for confirming my conclusions so far, Dom.  

  I've Got the Az rotator on the bench. It looks and smells new. The limit switches present a closed circuit until the swtich is activated when they open as expected.

  Looking for continuity between the pin corresponding to to A6 (black wire) and one of the limit switches (red wires) shows 3.7 ohms, and to the other switch (green wires) is an open circuit. I'm thinking this should be continuous also. If this is the case, what are my options?  Has anyone had success repairing this motor? 

  Thanks for the help.
  John Meeks

  Hi John, KC8ZFN

  Disconnect momentarely the electrolitic capacitor C34
  If the rotator is into an intermediate angular position the limit switches SW6 and SW7 are not activated and so they are in a normally close condition and must show a close circuit or zero ohm

  Looking for continuity between the common of the motor winding A6 and directly to each end of both motor windings you must measure the same continuity with a resistance of 3.6 ohm

  In addition you must measure the continuity and 3.6 ohm between A6 and both at the input and at the output of each  limit switch SW6 and SW7

  Measuring the resistance across each limit switch when the rotor is into an intermediate angular position you must measure zero ohm if SW6 and SW7 are OK since they are normally closed.

  If the limit switches SW6 and SW7 are OK then the motor winding showing an open circuit must be rewired because of a possible interruption somewere into the winding.

  Since you have the rotor over the working  banch it should non be difficult to locate the interruption.

  If one motor windind must be rewired it is possible to rewind it by hand because there are not a great numbar of turns for 24 volt AC

  Please let me know. 

  73" de

  i8CVS Domenico  


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