[amsat-bb] Re: Kenpro elevation rotor repair

[i8cvs]

Hi Sebastian, W4AS

Electrical causes:

Before to open the rotor check if the starting capacitor C35 for the 24 volt
AC motor is OK

Looking at the schematic diagram of your G-5400B rotor you will see
that the starting unpolarized electrolitic capacitor C35, 100 uF is located
inside the elevation rotor.

While running UP the rotor the voltage measured between the common
of the motor numbar E6 and numbar E5 must be about 24 Volt AC and if the
voltage measured between E4 and E5 is about 24 volt AC it indicates that
the electrolitic capacitor C35 is not short circuited and both windings
of the motor are OK

While running DOWN the rotor the voltage measured between the common
of the motor numbar E6 and numbar E4 must be about 24 Volt AC and if the
voltage measured between E4 and E5 is about 24 volt AC it indicates that
the AC electrolitic capacitor C35 is not short circuited and both windings
of the motor are OK

If the motor don't runs in any of both direction UP and DOWN disconnect
the wires of the control box from terminals E4-E5-E6 of the rotor and
measure the ohmic resistance of the motor windings.

If C35 is not short circuited you must measure the following resistances
for the rotor windings.

Between terminals E4 and E6:  5 ohm
Between terminals E5 and E6:  5 ohm
Between terminals E4 and E5:  10 ohm

If the motor still don't run check C35 100 uF and measure it's capacity
in uF because even if the voltage across it as measured between terminals
E4 and E5 is 24 volt AC it can be an open capacitor.

If the above C35 must be replaced and you decide to open the rotor remember
that the manufacturer has used  liquid "loctite" into the treads of the
screws.

To remove each screw do not attempt to use a percussion screwdriver
but it is necessary to heat the head of the screw using a small gas flame
after that a small wise grip size 5WR immediately applied is enough.

Mechanical causes:

In general the elevation rotor stuck mechanically when the ball bearing
holders are defective because one or more teeth of the ball separators
are broken.

When the ball separators are broken then the boom shaft tube falls
down a litte bit so that the assembly tube gear do not engage anymore
into the teeth of the final pinion of the gear box

Each bearing has 20 balls and since the ball separators are difficult to
find and they are a source of problems I have removed that separators
addeding I don't remember if 2 or 3 more same size balls to compensate
for the room of the above ball separators.

In any case as soon the rotator is open you will be in condition to find the
problem by your self.

Reassembling the rotator set the 500 ohm potentiometer with the wiper
at 250 ohm each side and position the mark over the cast of the boom shaft
tube for 90 degrees elevation.

Have fun and 73" de

i8CVS Domenico

----- Original Message -----
From: "Sebastian" <w4as at bellsouth.net>
To: "AMSAT BB" <AMSAT-BB at amsat.org>
Sent: Saturday, September 27, 2008 5:01 PM
Subject: [amsat-bb] Kenpro elevation rotor repair


> Well I had been back on the birds for the last 3 months or so, and
> while I was getting ready for an AO-16 pass a few days ago, my
> elevation rotor on my Yaesu G-5400B stopped at about 10 degrees.
>
> That's it.  It won't go back down or up.
>
> So I checked the wiring on the rotor, everything appeared fine.  I
> removed the elevation rotor from the azimuthal, and took it inside.  I
> made a small patch cord to go from the control box to the rotor, but
> no luck.  All I get is the display of the elevation of about 10
> degrees, and I hear a little hum when I attempt to move it up or
> down.  This tells me that the potentiometer is probably good, and the
> motor is receiving power.
>
> I've removed the small nameplate on the side, and there is no water
> inside, and I can see the ball bears; there doesn't appear to be any
> rust inside.  I also removed the terminal assembly in case one of the
> wire had come loose, or had a cold solder joint, but I didn't find any
> problems there.  Looking at the diagram of the rotor, there appears to
> only be a small 24 volt motor which turns this; along with numerous
> mechanical parts.
>
> So the question is.  Before I send this to Yaesu, has anyone had this
> problem before, is it a minor one (something that I could fix myself),
> or is best left to Yaesu?  Before anyone mentions, Norm's no longer
> services these rotors.  The four 'screws' that hold the two parts are
> impossible for me to loosen.  I would have to use a vice, but I do
> have a friend with a motorcycle repair business who I'm sure could
> open it for me in 60 seconds.  To me, this looks like a jigsaw puzzle
> by looking at the diagram.
>
> The rotor was in service for about a couple of years back in the early
> 90s.  It then sat inside without any use, up until a few months ago.
> If the consensus is to send it to Yaesu, should I bother to send in
> the azimuthal rotor, or should I follow the "don't fix it if it aint
> broken" rule?
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