I decided to see what I could do to fix my Ham IV rotor noisy readout until I
could change out the rotor and rebuild/replace the readout pot inside the
rotor. Delivery of the part from Hy Gain is 2+ weeks (minimum) so that probably
means I'll get it in mid January.
I tried this simple fix. I used a 12 Volt bulb (automobile lamp, ~1/2 Amp) in
series with 12 Volts connected to the 300 Ohm readout pot as follows. Jumpered
both ends of the readout pot together (rotor wire #3 & #7) and connected thru
the bulb to +12 Volts, negative 12 Volts to the pot wiper common #1 ground
terminal. The bulb will limit the current to ~1/2 Amp so I don't burn out the
pot. Then run the rotor from end to end limits twice. Bulb only lights up as
the wiper gets to either end of rotation, the bulb limits the current. Less
current flows (minimun ~80 mA when North) during the rest of the rotation due
to the pot's parallel combination resistance. Anyway, I did it end to end
twice, then reconnected all back to normal and, bingo - it cleaned up the
problem. Now my readout is smooth and continuous - like new !!! I guess a small
amount of dirt or corrosion had built up after ~20 years of use and the normal
readout circuit current is too small to burn/clean away dirt on
the pot/wiper.
The end result is I don't have to remove/rebuild the rotor and of course, now
I'll have spare parts (insurance) that I won't need now. More stuff to put on
the shelf and never find it again. Time will tell how well this fix will last,
hopefully until sometime after the January contest.
73's
George, WA2VNV
50 thru 1296
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