[amsat-bb] Re: Yaesu 5500 rotor problem

Jeff KB2M kb2m at comcast.net
Wed Jul 20 18:25:04 PDT 2011

Thanks for all the replies on my 5500 rotor problem! I had some time tonite
to work on it and here's what I got. On both a1 a3, and e1 e3 pairs I'm
reading only 1.0 volts. Between a2 a3 , and e2 e3 pairs I see only .5 volts
at half range, IE an elevation of 90 degrees =  a reading of .5 volts. I'm
going to order a new Q2 UA7806C and this should do it. Only question I have
is why Q2 failed to only output 1 volt, don't they usually fail and output 0
volts? I'm thinking it might be something else in the circuit feeding power
to Q2. If so I will work this further when I actually take the rotor box
apart with the new Q2 in hand. One other thing, I wish I can find all my
components' I boxed up when I moved. I bet I have 10 of these in stock :)
Thanks again for all the help guys, the electronic copy of the manual was a
big help as I can't find my copy....

73 Jeff kb2m 

> I'm having a problem with my 5500 after a thunderstorm. What is happening
> is that the rotor works manually, but doesn't display az and el
> on the control box. Also when I try to use computer control it goes all
> way to stop in both azimuth and elevation. I'm thinking this might be in
> control box, as both az and el are doing the same thing, the control box
> being the single point of failure. Did anyone ever have this problem? How
> can I diagnosis what chip might be at fault without a schematic. I vaguely
> remember having this same problem after a close  lightning strike with my
> prior az el Yaesu box about 14 years ago but don't remember what chip I
> swapped out, or how I determined which one was at fault. This getting old
> thing really sucks. Any help would be appreciated.
> 73 Jeff kb2m

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