Mystery Gyro G401B (HK401B) modifications

The Mystery gyro G401B (sold by DealExtreme, HobbyKing, xmseller, etc) requires some modifications before using it. It's a $20 gyro $14 gyro, so don't expect it to have the same build quality of a $150 Futaba GY401 :P Two major problems were reported in the G401B forum threads:
  • The gyro circuit board is not firmly attached to the plastic case, causing problems to the gyro operation.
  • The solder joints of the tiny switch for digital/analog/normal/reverse mode can break off the board when flipping the switches.
Items required:
  • Hot glue gun (I used a small 10W dual temp gun)
  • Small piece of soft foam - 2.5cm x 2.5cm, about 0.8cm thick (1" x 1", 1/3" thick)
How to fix: It seems like a lot of work but this is actually a 5-minute job:
  1. Unscrew the gyro case lid and carefully remove the circuit board from the plastic case.
  2. Add hot glue to the solder joints of the switch block (both sides) so it is secure on the board. If you add too much glue, it will be harder to put it back (I had to carefully trim the excess glue with an x-acto knife).
  3. Apply hot glue to the servo solders on the board, so the wires are held not only by the solders. Don't let the hot glue gun touch the wires as they will melt.
  4. While you're there, apply hot glue to the solder joints of the two vertical circuit boards.
  5. Apply hot glue to each corner of the case and insert the board again. Use something long and thin (like a small screw driver) to press the board against the glue so it gets fixed on the plastic case.
  6. Insert the square piece of foam when screwing the case lid back. It will help keep the board in a tight, fixed position.
NOTE: Steps 3 and 4 are optional and might be considered overkill by some. I did them anyway as I didn't see any disadvantages.

Gyro circuit board, before applying hot glue:

Board glued and gyro ready to be closed:

Soft foam:


UPDATE 02/Dec/2010: Trainboy64 has posted a nice video on YouTube showing basically the same thing: