XJet

It's *not* the pot that centers the servo, the pot is only a feedback device that the amp uses to determine the position of the servo output.

The centering is down to the type of motor used and the deadband provided by the servo amp.

HS5645 servos have a pretty standard pot that is used in a *lot* of different servos (some very good, some not so good).

The real reason a 5645 isn't as precise as a coreless digital such as the 5945 or 5955TG is that it has a wider deadband and the 3-pole motor has very significant "lumps" in its torque output when expressed against the rotation of the rotor. ie: at some positions, the motor produces a *lot* of torque, at others it produces a lot less.

This means that if the commanded position corresponds to one of the "low torque" positions of the motor armature then it may not actually reach that position. It's also common for servos using cored motors to be designed with a wider deadband (ie: accuracy) to avoid them "hunting" back and forth. This is because the armature of a cored motor is *much* heavier than that of a coreless. It Simply can't start and stop quick enough to hold a very precise position without overshooting and oscillating back and forth. If you want to se what happens when you try to use a very tight deadband with a cored motor look at the TowerPro MG995 -- it's not pretty.

The *least* important aspect of a servo's centering is the pot itself I'm afraid.

But, back to the original poster's question...

The 5645 is a good mid-range digital servo. No, it won't center as well as a 5945 or 5955 coreless servo but it's a lot cheaper.

For most fliers (short of competiti9on IMAC) its resolution and accuracy will be more than adequate.

I have four HS645 servos on the ailerons of my aerobatic (Extra 330L) gaser (2 per surface) and they work perfectly well with no centering problems -- the digital version (5645) can only be better. About the only bad thing I'd have to say about these servos is that they are way too slow for my flying style on 4-cells and just "adequately fast" on 5-cells or A123s. (6-6.6V).

There is a lot of "religion" in RC gear but I buy mine solely on what represents the best price/performance ratio.

I have Hitec transmitters for my beaters, a JR transmitter for my good stuff, receivers by Berg, LightFlight RC, Hitec, JR, and Polk, some Hitec servos, some OEM'd BlueBird, some Futaba and some JR.

I'm totally agnostic and brand disloyal so I like to think that my comments are totally objective.

JR servos are fine, but in the larger ones they just seem to chew gears at an alarming rate. It was for this reason that I went for HS5955TG servos for my gaser and I've not been disappointed.

Futaba servos are fine, but the price performance ratio (in the 120=150oz/in metal geared range) just isn't there.