[amsat-bb] G5500/G5500DC/G5400 Rotor Problems

[Burns Fisher]

BTW, although John's probably is probably not this (since the issue seems
to be around the control box), I did have a problem with mice chomping at
the control wire too :-)

On Mon, Oct 5, 2020 at 2:08 PM john--- via AMSAT-BB <amsat-bb at amsat.org>
wrote:

> You can go back through the amsat-bb archives and find many of the same
> problems that are being talked about now.  Yaesu rotor problems are not
> new and are re-discussed from time to time.
>
> I have a G5500 on my Arizona station.  It was installed in 2013 and it
> was a used rotor at the time.  It worked ok for several years.  I had it
> tracking Funcube 24x7 for many months and that was probably not a wise
> decision considering the potential problems.  A few years ago I started
> to experience what is being talked about now.  The azimuth readings
> started to be erratic.  The LVB tracker would give up trying to move the
> rotor and since I was not there to manually move it, I would use the
> park command in SatPC32 to try to get past the intermittent areas.  That
> would work for a while but soon I could not park the rotor from about
> 100 degrees back to zero.
>
> So the best option for me was to buy a replacement azimuth rotor (no
> control box or elevation rotor).  This was a catalog item at many ham
> radio supply houses.  So last December my son and I replaced the azimuth
> rotor with the new Yaesu unit.  I thought I would be good for a few
> years but that would not be the case.  I planned to repair the original
> az rotor by replacing the pot and have it available if the rotor should
> fail in the future.
>
> In August the rotor started showing signs of the same problem.  I
> noticed that the actual azimuth was lagging behind what SatPC32 was
> sending to the LVB tracker.  Eventually it would get past the bad spot
> and movement would be normal until it got to another bad area.  So the
> new rotor only lasted 8 months and I wasn't tracking and downloading
> data on any satellite.
>
> So what is different about Arizona?  For one thing the temperature gets
> to 120F and when the sun shines, as it does most every day, the dark
> cclor of the rotor absorbs the heat and the temp inside the rotor is
> likely sky high.  Could that be a reason that the potentiometer is
> failing?  Maybe and maybe not.
>
> Several years ago I ordered replacement pots from Yaesu.  The shaft on
> these pots is metric so 1/4" American made pots will not fit.  You are
> stuck with metric components.  The part number on the replacement pots
> is RA25Y25S B501.  You can look it up on the web.  The specs for this
> pot are 15,000 cycles and 100 degrees C.  I doubt if the temp inside the
> rotor exceeded 100C so it should have held up in the Arizona sun.
> 15,000 cycles is a lot and you can do the math.
>
> The next question is what is the part number of the pot in my new
> azimuth rotor?  Did Yaesu change suppliers over the years and what are
> the specs of the pots they are using now?  Once I disassemble the old
> rotor which is in Arizona, I will know if the part number is different
> than the replacement pots I purchased.  I could send the new rotor back
> to Yaesu under warranty and have it repaired, but why do that if the
> same pot is used to repair the unit and will likely fail again?
>
> I thought I was alone with this problem but after asking around I found
> that that might not be the case.  KB6LTY is experiencing the same
> problem with a new G5500DC that she purchased not long ago.  There
> appears to be a systemic problem here.  Changing the pot may work for a
> while but you can't be taking things apart every year just to have the
> same problem occur shortly thereafter.  K3RRR reported similar problems
> and his story should be told here as well.
>
> Last year Yaesu changed the model number of the G5500 to the G5500DC.
> There was no announcement and ham radio dealers knew nothing about the
> change.  EA4TX who makes replacement control boxes was also unaware of
> the change.  The motors in the rotors are now DC rather than AC.  The
> controller is different, but Yaesu did not publish the schematic in
> their instruction manual as they did with the G5400/5500 series.  One
> satellite operator noticed that when SatPC32 sent a command to move the
> az and the el at the same time, the control box would go into a fault
> condition.  Apparently the control box detected an overcurrent condition
> due to a high startup current and shut down.  I'm not sure if that issue
> was resolved by Yaesu or by a software change.  Just another thing to be
> aware of if you have a new DC model.
>
> Another thing to be aware of is that there are meter amplifiers in the
> the control box that are used to isolate and control the output voltage
> to interfaces like the LVB tracker.  These meter amplifiers can become
> erratic rendering the interface unusable.  The meters in the control box
> are separate so if they are reading properly and don't jump around,
> erratic readings going to the computer interface are likely caused by
> the meter amplifiers and have nothing to do with the pots in the rotors
> themselves.
>
> If you have experienced these kinds of problems and have or have not
> resolved them, please post so that we can determine how widespread these
> issues are and possible fixes.
>
> 73, John K8YSE
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