Re: [amsat-bb] Lessons Learned: Yaesu G-5400B

[Jim Doyle <kd4hur@xxxxxxxxxxxxxxx>]

Jerry:
	Welcome to the Yaesu-Kenpro Rotor Rebuilders Club!
	We all have to learn this one lesson only once.
Jim KD4HUR

K5OE@aol.com wrote:
> 
> A few (long) weeks ago, my elevation rotor failed.  What follows below is a
> brief description of my journey into the world of gears and grease, plus some
> lessons learned along the way.
> 
> First a little history.  I bought this rotor last year on eBay while I was
> still in Russia.  My wife sent the fellow money and he sent the hardware.  It
> was a bargain (at least it was then).  When I got home and tried it out, the
> manual controls worked fine, but the meters did not.  I traced the problem to
> a failed voltage regulator:  an oddball if there ever was one... a 7806.  I
> put in a 7805 from RS with a diode on the ground leg to bias the output and
> it worked fine for displaying the position.  So I thought.  A few months
> later I added a Uni-Trac controller.   When the Uni-Trac commanded the
> controller to move the rotor(s), the voltage drop across the diode caused a
> slight dip in the output voltage, which screwed up the A/D count back to the
> Uni-Trac, creating a hunting effect.  Finding and installing a 7806 rectified
> the problem.  This is known as Lesson # 1:  1 Volt does make a difference.
> 
> Fast forward 10 months later...  The first thing I noticed wrong was my UO-22
> downlink was terrible.  I first thought maybe I forgot to turn on the rotor
> controller power.  It was on, but I noticed the elevation display was reading
> zero when it should have been up 20 or 30 degrees.  I ran outside to see what
> the antennas were really doing, and sure enough, they were horizontal (duh!)
> .  When I returned to the shack I noticed the controller box had the distinct
> smell of ozone (always a bad sign).  I immediately put them in manual and
> started to bring them around to where I park them.  Before I got there,
> though, a loud pop preceded the displays going to zero--not a good sign!
> This is known as Lesson # 2:  hit the big red switch at the FIRST sign of
> trouble.
> 
> Immediate troubleshooting indicated replacing the fuse was futile as powering
> the unit blew the fuse each time.  After partially disassembling the
> controller, I determined the transformer was bad.  It should have dawned on
> me at this time that a bad transformer would have affected both rotors (az
> and el), but I was looking for easy answers (who isn't?).  After sourcing the
> transformer locally (thanks K5GNA), I replaced it and then figured out
> something was actually wrong with the el rotor--but at least I could rotate
> in azimuth.   I also noted on the schematic, the 11 V secondary of the
> transformer was to power a couple of meter lights.  I didn't know these
> things had lights!  I replaced the two bad grain-of-wheat bulbs with RS #
> 272-1092C micro lamps.  They work great and now I have a night-light.
> 
> Next, I pulled the el rotor off the az rotor and took it into the garage.
> Taking this rotor apart was almost beyond human capability.  I resorted to an
> impact screwdriver and a 3 lb (1.36 kg) sledge hammer.  With the rotor
> secured (bungy cords) against the metal rails of my garage door and resting
> squarely on the concrete floor, I had to smack each screw at least a dozen
> times, some many more times, to break them loose.  One refused to budge, and
> I was literally drained (it is hot and humid here), so I finally quit cursing
> and set the whole damn thing in my vise and used a hack saw to remove the
> head of the last screw.  I saved it as a momento to my prowess and vigor :-)
> Lesson #3:  if you have yours down for any reason, even if it is new, take
> the screws out one at a time and apply anti-seize to each one.
> 
> The next job is taking out 4 screws to remove the assembly from the housing
> halves.  These also required the impact screwdriver.  One of them is obscured
> by the motor, so I had to remove the motor and the motor mounting plate to
> access it with the impact driver head (a regular screwdriver could reach it
> but could not budge it).  Lesson # 4:  don't remove that mounting plate
> unless you enjoy rebuilding a complex set of gears (without any instructions).
> 
> I did not find the kind of rust inside as described by others.  The rotor
> mechanicals, despite the indeterminate age, were in fine shape.  The housing
> showed no signs of rust and the bearing balls were likewise in good shape.
> But, the motor was nonfunctional.  It would hum, but that was all.  I was,
> luckily, able to find a replacement motor--sort of.  I found the motor that
> goes to the G-5600, which appears pretty much the same except for 3 mounting
> studs.  They were removed with a hack saw and the motor installed.  Why
> didn't I just get the replacement motor from Yaesu?  I'm still waiting for
> them to return my calls with the price.  Lesson # 5:  they will take your
> order, without confirming the price, but if you ask them to tell you the
> price first, they have to call you back because "they are so busy in the
> service department."  I'm still waiting.
> 
> What is clear now is the motor failed, which then caused the transformer in
> the controller to fail, which then popped the fuse.  I had the specified 2
> Amp fuse in the unit at the time of failure.  Pretty poor failure protection.
> 
> I followed the recommendations of the many prior postings relating to
> cleaning, reassembly, grease, and gasket sealer to good effect:  the unit has
> been up working like new for a few days now.   Fingers crossed.
> 
> One last item:  I noted the potentiometer shaft was rotating freely about the
> gear that slips over it.  It is held by just a set screw--some odd size Allen
> wrench (that I don't own).  This is a really lousy design.  The shaft should
> be notched flat at least to set the screw against.  I suspect this was the
> initial failure mechanism, but the mechanical limit switches and stops should
> have cut the motor off.  Hard to say now...
> 
> 73,
> Jerry, K5OE
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