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RV-12 trim servo voltage

Phantom30

Well Known Member
Have had problem with elevator trim servo...after paint job only works when it wants to😎....I ordered a new one, and am installing it (waiting for new micro pins)..so I thought I'd do some trouble shooting.

When I measured voltage..I get 4.9 volts. Seems kind of light to me. Is there an adjustment in Van's majic box that I missed?

I have Garmin G3X with 305 auto-pilot control. Help would be appreciated.
 
The voltage supplied to the servo is a pulsed DC signal (PWM) for controlling the speed.

It can not accurately be measured with a common volt meter.
 
Scott and others: If the stabilator trim servo tends to run very slow and sluggishly at times, and other times will just barely run at all, what would you look at first?
 
The voltage supplied to the servo is a pulsed DC signal (PWM) for controlling the speed.

It can not accurately be measured with a common volt meter.

Thanks Scott....in the back recesses of my mind, I remember you saying this before. What or how would one check correct output to the servo? Also, is there an adjustment?

Edit: When in doubt...read the instructions. Page 45A-10.. adjust trim pot counter clockwise (I'm assuming this increases voltage)..thus, the servo runs faster.

Is this a corr
 
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The voltage powering the trim motor is pulsed 12 VDC, not steady DC. Many voltmeters will display the average voltage. If the voltage pulses are on for 1/3 of the time and off for 2/3 of the time, then a voltmeter might display 4.9 volts even though it is actually pulsed 12 VDC.
 
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The voltage powering the trim motor is pulsed 12 VDC, not steady DC. Many voltmeters will display the average voltage. If the voltage pulses are on for 1/3 of the time and off for 2/3 of the time, then a voltmeter might display 4.9 volts even though it is actually pulsed 12 VDC.

Thanks..Joe's (both)...now I know!!
 
If you have an O-scope you could see what the voltage waveform looks like at the servo. I still have the one I got in a GI Bill correspondence course 40'years ago. Every once in a while I pull it out and see if it still works.
 
Oscilloscope

Rich
You can buy a Rigol DS1054Z for the price of a good Multimeter.

Take a look at this video

https://www.youtube.com/watch?v=ETCOhzU1O5A&t=525s

I think I will order this one next week it is only $400

What do you think.

Joe Dallas



If you have an O-scope you could see what the voltage waveform looks like at the servo. I still have the one I got in a GI Bill correspondence course 40'years ago. Every once in a while I pull it out and see if it still works.
 
I wish you guys wouldn't post this stuff --- now I want one and have to convince my better half the universe will end if I don't get it!😁
 
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