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I've had this problem for a long time and finally got around to asking for any suggestions.

I only have limited left and right steering and want to know if it might be the radio? It also sounds like the servo isn't getting full power when turning, but it works fine with other radios. I've tried it with four different servos and three different receivers but the results are the same.

All of the adjustments on the radio are set to maximum throw/movement, but it only moves the servo 1/3 to 1/2 of it's max.

Any help would be appreciated.

if you have tried the same transmitter with different servos and receivers, it is almost positively the transmitter.

depending on the vintage of the radio, it is certainly possible that the full scale adjustment for the modulation is out of whack, or the modulator circuit itself has a problem. With AM radio, the movement of the (steering)wheel will change the voltage level on a signal that modulates the rf carrier(75Mhz?) to give you what's called the depth of modulation. With an old analog circuit, it could be a trim pot adjustment that is out of whack, or a dried up electrolytic capacitor, or burned out resistor, etc, etc, etc. it's certainly possible that the potentiometer that is the wheel itself is faulty as well. Maybe your voltage regulator on board is low, which will directly affect the operation too.

so to summarize, there is something wrong with the modulator circuit that requires troubleshooting with electronics test equipment.

Have you turned the thumb wheel by the trigger all the way up? It is kind of hidden and I wasn't positive it was there till I looked at the one I had in the garage.

I had him check that already that was my thought too

Remove the back cover and see if the antenna catch clip may be broken and limiting the pot to turn completely has to be in this area.