The Telebee heading hold gyro has been proven to have outstanding performance for its size and low price. The gyro detector package is not much larger than a standard piezo gyro, and the price is comparable to one without heading hold. It does have a separate module attached to it (similar to the microprocessor module of the Futaba GY501) called the "Gyro Control Amplifier" that occupies a fair amount of space, however.

The good news is that the Gyro Control Amplifier module can be eliminated. It has nothing more in it than a PC board used to provide a convenient attach point for some header pins, into which the receiver and tail servo plug. The only components on the board are a resistor and capacitor used to filter the high current spikes (caused by the servo motor drive) from the supply current feeding the gyro detector electronics. These two components can be absorbed into the gyro package, completely eliminating the need for the large module. A couple servo extension wires will be cut up and hardwired into the gyro body. The receiver and tail servo will then connect directly to these wires.

A closeup view of the Gyro Control Amplifier

Steps for Modification

1. Disassemble the gyro detector case and the amplifier module.
2. Snip the tiewrap strain relief on the gyro PC board.
3. The glop gluing the wires to the board is hard to remove. Just start unsoldering the five wires and the material will be easy to pick off with tweezers.
4. If you have a solder sucker or solder wick, use it to clean the solder pads and remove the solder in the holes in the center of each pad.
5. Prepare three servo leads to whatever length you want for your installation (two males and one female). Separate the wires about 15mm from the cut end, and strip about 3mm off the ends of all nine wires. Tin the wires with solder.
6. Carefully remove the resistor and capacitor from the "amplifier" circuit board (they will be reused.). If you want to use parts lying around, the resistor is a 1 ohm (be sure to use the same wattage) and the cap is a .01 microfarad (104).
7. Viewing the detector module with the switch in the lower left corner, solder the resistor vertically to the leftmost of the 5 solder pads.
8. The capacitor is soldered to the same leftmost pad and to ground. Most of the solid copper areas around the traces on the board are ground. Just look for anything that is connected to center of the five pads (where the black lead was connected). If you want to solder to a green area, you’ll have to scrape off a bit of the solder mask. There are several exposed areas where you can reach a ground.
9. Solder the modified servo extension leads as shown in the drawing.  The white or yellow wires are the signal lines.  The red is the positive supply and the black is the return for both the signal and power.  The white (yellow) wire from the female connector pigtail (tail servo) goes to pad #5 (the rightmost pad).  The white (yellow) lead for the AUX channel goes to pad #4, and the white (yellow) lead for channel 1-4 goes to pad #2.  All the black wires connect together and solder to pad 3 (in the center).  The red wires from the female pigtail (tail servo) and the RCVR CH 1-4 pigtail solder to the top end of the 1 ohm resistor,
10. Stack the three wires neatly where they will exit the case, and tiewrap them to the original holes in the PC board. Pot the wires to the board with Goop or hot melt glue.
11. The slot in the plastic case where the wires exit will need to be carved a little higher with a Dremel tool or an exacto. Try to eliminate any sharp edges that would cut the wires over time.

Unfortunately the modification of my gyro was over before I thought to take any step-by-step photos. The drawing and the final photos should explain what I missed.

Here's a pictorial drawing of how the wires connect to the gyro board.  It works out better if the wires attach to the pads from the top instead of from the bottom (as shown for clarity).  This gives room for the cable bundle to get tiewrapped to the board while leaving a little strain relief loop on each lead.

The gyro detector with the new leads attached.  The two on the right plug into the receiver and the one on the left accepts the servo plug.

 

 

The detector case slot has been modified to accommodate the slightly thicker wire bundle.

 

 

Here's a nice detail of the wires glued in final position.  Note the placement of the 1.0 ohm resistor on the gyro board.

If you have no experience with heading hold gyros, here are a few suggestions:

1. If you want to operate in heading hold mode at all times, you can just use the rudder trim or subtrim to reach a null where the tail servo will not drift one way or the other. Just make sure that revolution mixing, or any form of mixing that feeds into the rudder, is disabled in all flight modes.
   
2. If you are a beginner and want to be able to switch between conventional and heading hold modes (since heading hold can get you in trouble when venturing into forward flight), setup is a little more complicated.

1. Revolution mixing must be off whenever the gyro is in heading hold mode.
2. In heading hold mode, set the rudder subtrim on your transmitter so that the tail servo does not drift (with no stick input)
3. Do not touch the rudder subtrim from here on out, except to correct for minor servo drifting.
4. Test fly, and note direction of rotation with no rudder stick input while in heading hold mode.
5. Change tail rotor pushrod length as needed to stop rotation in heading hold mode with neutral rudder.
6. Minor differences in trim required between conventional and heading hold modes should be compensated using rudder offset (not subtrim) that is programmable with each flight mode on your transmitter.

3. There are advantages to keeping the conventional/heading hold control on a separate switch rather than linking it to your flight mode switch. If you should find yourself disoriented a long distance away, flipping off the heading hold will at least ensure that the tail will weathervane, greatly increasing your chances of bringing the heli back alive.