AGF servo A73BHLW V2 buzzing at idle

[Partydaz]

Greetings ,

I recently treated myself to a AGF A73BHLW V2, love it as the thing is wicked fast and crazy strong but I noticed a very slight buzzing at idle and when in use, end points set correctly so Is this normal for these ?.

First posh servo for me have always had cheapos off AliExpress so use to noisy servos anyway, this is much quieter than any of them and wondering should I send it back before it blows up ?, I think I am being overly cautious because how much it costs I know its nothing compared to what servos can cost but for me its a pricy servo .

Cheers

 

[Nelson.81]

Don’t know if mine buzz, not something I’ve noticed ,when power up my fans all I usually hear. Next time I fire it up I’ll stick my ear to it.

 

[Fireblade]

Partydaz, am I going mad, or did you reply to a thread on here with links to some cheapo servos? I ordered one last night for £22 to use while my wallet recovers from destroying a motor after 3 packs.

 

[Fireblade]

Found it! Modelsport forum, not here.

 

[Partydaz]

What motor did you blow up?

 

[Fireblade]

Hobbywing Ezrun 4278, it didn't blow up, the pinion slipped then stuck and I basically fiddlesticked it trying to get the pinion off.

 

[Atomic Skull]

Servos sometimes do that especially if they have low deadband and the pulse width of the control signal from the receiver is slightly jittery. Most AGF servos are programmable so you could try increasing the deadband and see if it still does it. It's usually caused by the servo chasing the control signal while at rest.

EDIT: Deadband is the minimum amount the control signal pulses must change before the servo recognizes it and triess to move, anything below the threshold is ignored. This is usually 1 or 2 milliseconds. Control pulses range from (about) 1000ms wide to 2000ms wide plus a little extra for subtrim. Center is usually considered to be 1500ms or 1520ms (Futaba uses 1520ms and a lot of other manufacturers follow that). The signal is a square wave of variable duty cycle (width of the square wave pulse) with a frequency of (usually) 50hz. Most digital servos can handle up to 333hz, older analog servos almost always used around 50hz refresh rate and most receivers still output a 50hz signal by default. Higher refresh rates (e.g. 333hz) only matter for gyro controlled servos you won't notice a difference for a "manually" controlled servo especially in a car (in a helicopter or an aerobatic plane this is more debatable)

The pulse width of the square wave is never perfectly stable, it jitters very slightly, especially in older radio systems so deadband is needed to keep the servo from chasing the pulse with of the signal while at rest.

,EDIT: You may be wondering what the deal with "narrowband" servos is, these are servos that can run at a refresh rate higher than 333hz. At around 400hz the pulses in a 1000~2000ms duty cycle control signal will start to run together so if you want a higher refresh rate you use smaller width pulses, say 250ms ~ 1250ms and then call 760ms the center. This gives you much more "overhead" for increasing the refresh rate of the control signal. This is really, *really* only relevant to gyro controlled servos and arguably only important for helicopter tail servos (and maybe not even that much as some helicopter flight controller developers have claimed that anything higher than around 180hz is pointless)