HITEC General Servo - Manual (Page 2)

The Hitec AM, model HAS-02MB, HAS-03MB and HP-2RNB receivers are built with a
BEC or battery eliminator circuit built into the battery port of the receiver. This will limit
the amount of power some of the larger servos can draw from the receiver.
It is suggested that using these receivers with large power consumption servos like the
HS-805BB, HS-815BB or the high end, premium coreless motor servos and digital
servos, a "Y" harness be used to connect the receiver battery / switch harness and servo
to the receiver. Typically this is done by connecting one of the upper "Y" connectors to
the servo, the other upper connector to the switch harness and the lower "Y" connector
into receiver port 1,2 or 3, depending on what channel you wish the servo to operate.
This will allow the BEC to be bypassed, your large servo will always have power and the
rest of the servos and the receiver will be powered from the port you plug the "Y" into.
Modern coreless and digital servos have impressive torque values. This takes a lot of
power. Receivers are capable of delivering only so much power to the servos plugged
into it before the voltage draw down caused by the servo power consumption falls below
what the receiver requires to "hear" the signal from the transmitter. When this occurs a
"glitch" will result from loss of signal to the receiver. Large aircraft can easily use 6 or
more powerful servos with some 1/3rd scale planes having multiple servos per control
surface. There are several answers to this issue. Many modelers choose to use two
receivers and others power the servos with a separate battery from that of the receiver.
The point here is to be cautious when "Y" harnessing or "ganging" powerful servos toge-
ther. Using larger capacity Nicad batteries as well as Heavy Duty switch harnesses are
highly recommended in these applications.
Use only specially designated servo grease when replacing servo gears. Using other
type of grease not intended for servo gears may produce gas when used in sealed cases
which may coat a nasty film on the motor brush that could stop the servo operation.
We would like to strongly discourage you from ever working on the coreless motors.
Unlike conventional cored motors, the brush base of the coreless motors is extremely
fragile and can be easily separated from the Printed Circuit Board. This is best left to
authorized service technicians with the proper equipment.
How to by-pass the BEC circuit on the HAS-02MB/03MB and HP-2RNB receivers
Too Many Servos
PRINTED IN KOREA
Servo Grease
Coreless Motor Care
Servo makes a grinding noise or acts erratic: Open the case and remove the gears.
Examine them for broken teeth. If broken, replace with a new gear set.
Servo jitters: This may be a dirty potentiometer. Open the case and remove the gears.
Spray a zero-residue tuner cleaner into and around the "pot" and work it in.
Once the cleaner has dried, re-install the gears and close up the case.
Checking Servo Centering: Remove the servo from the plane or vehicle. With the arm
still attached to the servo, place an ink dot towards the end of the wheel and another
one on the case, these should be lined up for a reference point. Plug the servo into the
receiver and move the corresponding transmitter gimbal stick or wheel from stop to stop.
After each movement, check the reference points for alignment.
Servo is locked in place: Open the case and make sure the gears are properly aligned.
Next check the case top for wear. If wear is evident, replace the case.
Servo hums under load: This can be normal, the servo is trying to hold position against
the force of a load. If it hums when no load is applied, try loosening the servo case
screws a quarter to a half a turn.
Servo gets hot: Get out the fire extinguisher! Check the servo wiring, it should match
the receiver being used. The motor could be stalled due to a failed geartrain. Actually
several things could be wrong, this sounds like a candidate for the service department.
Servo Trouble Shooting
This is done so you can refer back to their positioning as you assemble the new set into
the lower servo case. Clean all the old lubricant from the servo case in both the lower
and upper case components. Be aware of small chunks of gear material that may be
lodged in the lubricant and get it all cleaned out. Apply servo gear lube to the shafts and
assemble the geartrain applying lube to all gear components. When complete, pop the
case top back on and tighten up the case screws.
CAUTION: Do not force the case top back on. If it will not fit back on smoothly,
chances are the gears were installed incorrectly.
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