[amsat-bb] Re: G-5400B

i8cvs domenico.i8cvs at tin.it
Wed Jul 7 00:11:45 PDT 2010

----- Original Message -----
From: "Liz & Tony Buckland" <buckland at scorch.co.nz>
To: <amsat-bb at amsat.org>
Sent: Wednesday, July 07, 2010 7:42 AM
Subject: [amsat-bb] G-5400B

> Hi All,
> I bought a secondhand G5400B and promptly dismantled both rotators to
> overhaul them and also completely repaint inside and out, and they
> now look like new :-).
> My question is I set the azimuth rotator as per the instructions and
> all seems good apart from the CCW direction does not indicate 180
> (far left), more like 165-170, is this normal? Mechanically it
> rotates more than 360 but the resistance of the pot is 14 ohms CCW
> and 8 ohms CW. I would have thought it should read 0 CCW then setting
> the adjust pot on the controller to 180 with the rotator exactly 360
> round CW. Hope I haven't lost anyone with this description :-).
> Any guidance would be most welcome, thanks.
> 73 de Tony ZL3HAM
Hi Tony, ZL3HAM

The resistance of the linear potentiometer is 500 ohm.If you disconnect
the wires A1-A2-A3 from the control box you must measure 500 ohm
between wires A1 and A3
When the rotator is fully CCW you must measure about 0 ohm between
wires A2 and A3
When the rotator is fully CW you must measure about 500 ohm between
wires A2 and A3
When the rotator is exactly mid way of its rotation i.e. at North or 360°
you must measure 250 ohm between wires A1 and A2 as well between
wires A2 and A3
If the above values are different it means that reassembling the rotator the
potentiometer was not set exactly to 250 ohm when the rotation is mid
way i.e. with the antennas oriented to North.
If this is the case remove the aluminum bell of the rotator and manually
balance the potentiometer with the wiper 250 ohm to one side and 250
ohm to the other side.
Than reposition and balance the aluminum bell for midway rotation 180°
toward CW and 180° toward CCW
It is best to perform the above measurements with the rotator on the banch
and not on the roof with the antennas.

I hope this helps

73" de

i8CVS Domenico

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