HAM-4 ROTOR TROUBLESHOOTING ADVICE

[William G Bithell]

On Mon, 6 Jan 1997 13:10:20 -0500 Tony Brock-Fisher
<fisher@hp-and2.an.hp.com> writes:
>HOLD ON A MINUTE!!!
>
>I think some folks don't understand what the capacitor does!!
>
>It is NOT a motor starting capacitor!!!
>
>The purpose of the cap is to cause a 90 degree phase shift
>across the windings of the motor, which determines which
>direction the motor wiill turn.
>
>Some old capacitors dry out and the value changes. This does result
>in the motor not starting to turn. Replacing the cap will make
>the motor work again. But replace it with the same value!!
>We have to assume Hygain/CDR knew what they were doing when
>picking the value. A larger value cap will allow more current
>to flow, but will also affect the phase angle, which will actually
>decrease the starting torque! An infinitely big cap would be a short!
>Do you think the motor would like that??
>
>And while I'm up here on the soapbox, I'm scratching my head trying
>to figure out how you can get away with back-to-back electrolytics?
>That combo would still have o DC bias across it, so the electrolytic
>would not be happy.
>
>The best idea I've heard yet is to move the cap directly to the 
>rotator,
>properly weatherproofed of course. This eliminates the cable 
>resistance
>inseries with the cap. Now use the two wires in the cable which went 
>to
>the cap, and double up on the motor wires, cutting the resistance
>down there two.
>
NOTE:  Double up on the motor leads NOT PINS ONE AND TWO
Pins 1 and 2   are a common and a wire to the brake solenoid.
the motor leads are on other numbers (Check your schematic)
>If anybody's interested, I've got some ideas on how to run Hygain
>rotators on 4 conductor cable. That way you could go 2-for-1 rotators
>on the same cable...
>
>-Tony, K1KP, fisher@hp-and2.an.hp.com
>
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