[amsat-bb] 5400B Rotor Problem
billbruno at earthlink.net
Sat Dec 22 08:28:24 PST 2007
First, many thanks to W7PN, VE4YZ and W0SAT for their help in
troubleshooting my rotor problem.
Problem: Both az and el indicators moved to just past the mid position with
the rotors moving full travel ( They moved all the time the rotors were
moving but at a slower rate).
Both indicators have the same circuitry differing only in the scale on the
face plates so all voltage readings should be the same for both az and el.
On the back of the controller, terminal 1 should read a constant 6 vdc.
Terminals 2 and 3 voltages will vary according to rotor position but added
together should total 6 v.
My terminal 1 reading was 3.2 v, approx half what it should be.
Following the circuit back towards the voltage regulator, R9 and R10 also
both read 3.2 v ( should be 6 v). At the voltage regulator (Q2 on the
diagram, Part # ua7806c) readings should be approx 16 v on the input pin, 6v
on the output pin, with the center pin ground. My readings were 16 v in, 3.2
v out, center pin ground, isolating the problem to the voltage regulator.
I hope this info can be of use to others.
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