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RE: Yaesu G-5400B Elevation Indicator



Dan,

The most likely problem is a broken wire in the sensing circuit.  With luck,
it will be on the back of the control box, or with less luck, at the rotor.
The worst case is a bad positioning potentiometer within the rotator itself,
or a broken wire somewhere between the shack and tower.

Turn everything off, unplug the control box, and disconnect the 3 wires from
the control box which are the position sense.  I have an earlier version of
that system, so I can't tell you numbers, but the schematic should be clear
enough.  The pot is probably 500 ohms, so you should find two or the three
wires that read with an ohm meter 500 ohms, or whatever the pot is.  See
schematic.  Assuming your antenna is approximately horizontal, the
resistance between the third wire and one of the others should be
approximately the full resistance, and to the other wire near zero.  If the
antenna is vertical, both the resistance should both be approximately half
the full resistance. If any of these wires reads open, you have found the
culprit.  If everything checks out, then you have an internal problem in the
unit.  If it doesn't, that is one reads open or less likely hard shorted,
you will have to check the connections at the rotor.  I would short all
three wires together in the shack, and take an ohm meter with me.  That way,
if all the connections look good, you can disconnect the same three wires at
the rotor and measure the continuity.  It should be near zero between any
two wires.  If it isn't then you have a broken wire somewhere in the line.

If all checks out ok in the wiring, then you can make the same resistance
checks at the terminal screws at the rotator.  If it fails the continuity
checks, then the positioning potentiometer is bad.  This isn't all that hard
to fix, but you have to take everything down to get to the unit.

Good luck.

Alan
WA4SCA

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