C band servo idle current

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N0QBH

Thread Starter
SatelliteGuys Pro
Jul 13, 2006
204
53
Central MN
Got an issue that recently cropped up with my C band signal and I suspect the polarity servo is going bad.
I'm measuring about 250 mA @ 5v to the servo while it should be at it's set position. That figure looks more like it is still trying to move or is cycling back and forth, but I thought I'd ask here - it's cold outside!
Either way, I'm waiting for warmer temps before I repair or upgrade to one of those voltage switched LNBs.
Mike
 

waylew

SatelliteGuys Pro
Aug 23, 2010
2,565
940
northern WEST new york
Try adjusting the skew a small amount and see if it stops,may be a bad spot in the position potentiometer.If you go out and listen you might be able to hear it growling.
 
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FaT Air

HOA Free Zone
Feb 27, 2010
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BITD most IRD's would shut off the 5 volts to the servo (after a predetermined time) because a worn/dirty potentiometer, that would cause this 'hunting', was and still is pretty common. Today with the availability of digital servos it's kinda surprising no one has employed them.
 

FaT Air

HOA Free Zone
Feb 27, 2010
6,668
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97W 48N
BITD If it's just a 'bad spot' in the servo and adjusting the skew slightly 'quiets' the servo you could 'fix' it by rotating the feed 5-10 degrees then repeak with the skew control. ( BITD many worked for years with this 'fix'. Those truely needing replacement only were quiet for a few months (the great minority)
 

N0QBH

Thread Starter
SatelliteGuys Pro
Jul 13, 2006
204
53
Central MN
The servo's worn out because I control it with one of my home brew coax voltage sensing servo positioners and I never turned off the servo pulse train in the code.
When doing the "predesign" I scoped out my Uniden 4400 and it keeps pulsing all the time, but at a reduced level??
That said, mine been running that way for 6-7 years whenever the C side was selected (by one of my other gadgets :)
Thanks for the input.
Aside from skew control, is there a performance difference between my Chapparal C band only lnb/feedhorn and Titainium's voltage controlled unit?
 

Titanium

AI6US
Lifetime Supporter
May 23, 2013
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The primary performance difference between a servo feedhorn and the Titanium Satellite LNBFs is the Chapparal's ability to fine-tune and optimize the skew for each satellite and polarity. The loss of the servo skew fine-tuning often makes the difference between a lock and no-lock on transponders that are weak or have interference. To compare feedhorns to LNBFs beyond that function is apples to oranges. So many variables with LNB specs and real world performance.

BTW... In the ASC1, we opted to time-out both the servo and the sensor circuits.
 
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