[amsat-bb] Re: G5400 elevation issue

[i8cvs]

  ----- Original Message ----- 
  From: Dave Webb KB1PVH 
  To: i8cvs 
  Sent: Tuesday, February 08, 2011 3:36 AM
  Subject: Re: [amsat-bb] G5400 elevation issue


  Domenico,

  The highest voltage that I can get at full 180° flip is 2.78 volts with voltage adjustment pot on rear of controller box. 


  Dave - KB1PVH

  Hi Dave, KB1PVH

  Make the following troubleshooting :

  Measure please the DC voltage across E2 and E1 with the antennas at full 180° flip.Since the  display on the control box reads correct elevation you must read about 5 volt DC.

  By the way since as measured between pin 1 and 8 of the external control DIN connector and with the voltage adjustment of pot VR4 you can get only 2.78 volt at full 180° flip it means that there is someting damaged across the operational amplifier Q4 4558 1/2 

  Since the pot VR4 is 10 k and there is a 4.7 k fixed resistor in series of it if you measure the voltage across VR4 you should get about 3.3 volt DC

  By the way measuring the voltage between the wiper of VR4 and the ground you should get a voltage change between 5 volt to 3.3 volt while rotating VR4 fully 270° back and forth

  If this is the case than the operational amplifier Q4 4558 1/2 do not correctly amplify the DC input signal applied to Q4 input pin 3 from the wiper of VR4

  Measure the DC voltage between output pin 1 an ground of Q4 and rotating VR4 by 270° back and forth you should get and amplified voltage greater than 5 volt DC and if not check diodes D22-D23-D24-D25 and all components connected around Q4

  If all components diodes-resistors and capacitors are nominal than it is possible that Q4 has lost amplification. 

  In this case change the 47 k feedback resistor R39 with a 100 k resistor and the amplification will increase at a point that flipping the antenna at full 180° the voltage across pin 1 and 8 of the DIN external connector will rise up to 5 volt DC or more.

  Have fun

  73" de 

  i8CVS Domenico                      





  On Feb 7, 2011 7:46 PM, "i8cvs" <domenico.i8cvs at tin.it> wrote:
  > ----- Original Message -----
  > From: "Dave Webb KB1PVH" <kb1pvh at gmail.com>
  > To: "AMSAT -BB" <amsat-bb at amsat.org>
  > Sent: Monday, February 07, 2011 5:16 PM
  > Subject: [amsat-bb] G5400 elevation issue
  > 
  > 
  > The display on the control box reads correct elevation, but on my digital
  > display on the Easy Rotor Controller shows erratic elevation position. I
  > have recalibrated it several times with no success. It won't read any
   > elevation until it is around 20° give or take. It also seems to have become
   > worse since our really cold temps set in. My best guess is the pot in the
   > rotor, but not sure where to start in the process.
   > 
   > Thanks in advance
   > 
   > Dave - KB1PVH