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R: 5400 Resistance Readings

Hi Rick, W2JAZ

I understand that you have the boom shaft tube removed for repair and
probably you have lost the mechanical calibration point related to the
potentiometer position.

I dont have a 5400B but the concept on my old KR 500 should be the

First of all look at both extremity of your rotatable shaft tube and you
should  see a longitudinal protuberant mark made in the aluminum.

Call this mark your 90 degrees EL reference point.

Now look at both side of the rotor housing and you should see the same
protuberant mark made in the aluminum cast wich this time is vertical.

Now, regardless in what position you have fastened the antennas to the
shaft tube rotate the motor until the mark on the tube and the mark on
the rotor hausing are coincident.

Now go back home to the control box,disconnect the AC power and
unscrew the wires 1-2-3 from the control box and live it connected
to the rotor.

If the mechanical-electrical calibrating position of the shaft tube with
reference to the indicating potentiometer is correct you must measure
approximately the following resistance values at the potentiometer.

1-2 = 250 ohm
2-3 = 250 ohm
1-3 = 500 ohm

Terminal 2 is the 500 ohm cursor of the wire wound linear potentiometer
and 1 and 3 are the extremity.

If the above measured data are great different I am sorry to say that
removing the shaft tube you have lost the mechanical reference position
between the big tube gear and the small motor pinion and the potentiometer
and if so you must remove the antennas and open again the rotor.

To get again the mechanical calibration point or 90 degrees Elevation
reference point is very easy.

With one shell of the rotor housing removed run only the motor gear box
until the potentiometer show the same value of approximately 250 ohm
between the terminals 1-2 and  again between terminals 2-3

Now insert the boom shaft tube in such a way that the big tube gear engage
with the gear box pinion while both reference marks are matching in the
same position and this is now the reference 90° vertical Elevation.

Put the rotor on the tower with the array pointing vertical.

I hope that your 5400 B is working with the same concept of my KR 500

73" de

i8CVS Domenico

----- Original Message -----
From: Richard J. Lawn <rlawn@uarts.edu>
To: <amsat-bb@AMSAT.Org>
Sent: Tuesday, July 27, 2004 1:12 AM
Subject: [amsat-bb] 5400 Resistance Readings

> I continue to be confused in repairing this 5400B EL rotor and I
> thank all those of you who have been trying to coach me through the
> repair. It was suggested that I take readings off EL terminals 1,2 &
> 3. I have the boom tube removed. I took readings at 0 at the control
> box terminals with power off and came up with the following:
> Pins 1-2 0
> Pins 2-3 3.7 ohms
> Pins 1-3 0 ohms
> readings at 90 deg according to the control box meter:
> Pins 1-2 243 ohms
> Pins 2-3 210.7 ohms
> Pins 1-3 0 ohms
> readings at 180 deg.
> Pins 1-2 45.7 ohms
> Pins 2-3 0 ohms
> Pins 1-3 0 ohms
> Another ham suggested that a good pot will read 0 ohms at 0 deg., 250
> ohms at 90 deg. and 500 ohms at full rotation to 180 deg.
> Another helpful ham reported the following readings from his healthy EL
> 0f
> Pins 1-2    237.2 ohms
> Pins 2-3      2.8 ohms
> Pins 1-3    235.7 ohms
> 90f
> Pins 1-2    184.5 ohms
> Pins 2-3    172.2 ohms
> Pins 1-3    234.1 ohms
> 180f
> Pins 1-2     24.2 ohms
> Pins 2-3    228.5 ohms
> Can anyone tell me what I should be reading from these pins? Am I
> reading values from the wrong pins? My AZ rotor is working fine so
> can I compare readings through the same panel meter rotation?
> I wish Yaesu would have been more helpful in the schematic as mine
> doesn't even show the two stop switches and does not indicate a value
> for the pot.
> Thanks for any additional help.
> Rick W2JAZ
> --
> Richard J. Lawn, Dean
> College of Performing Arts
> The University of the Arts
> 320 South Broad Street
> Philadelphia, PA 19102
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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