Tony's building thoughts

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Published on Friday, 20 September 2013 03:00
Written by Gordon Anderson
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Hi everyone:

For those of us building or contemplating building a Microstar 2000 transmitter, whether a single stick or a two stick, I have run across a couple of things that you might find useful:

  1. Pushbuttons: I used a snap action pushbutton from Digikey, C&K # 8121, that has a definite snap feel to it. However, the press on plastic button cap does not allow the stem of the switch to fully depress. I sanded 0.030 inches off the bottom of the plastic cap so the stem could be fully depressed. On the other hand, a couple came through with a long stem that I filed down so the plastic cap would not be sticking out too far. Each button cost $7.00 and the caps just a few cents each. The caps are available is several colors but only black were available when I ordered them. I think I like the all black plastic items better than a multicolored array.
  2. LCD: The LCD that came with the encoder kit I bought from Kees had the connection at the end of the unit. This caused me to have to crowd the LCD close to the gimbal making the location unsymmetrical in the space between the gimbal bezel and the edge of the case. Big deal but it bothers me a little. When you order the kit from Kees make sure the LCD has the connector anywhere other than at the end. It was too late for me to switch because I had already cut the opening for the LCD in the front of the case.
  3. LCD Mounting: I tried a couple of approaches to mounting the LCD including a stack of washers to separate the LCD far enough into the case so that the trim window will fit flush to the front of the case. I ended up fabricating a plywood spacer that I sanded down until the LCD was exactly spaced to allow the window to properly fit. I used 2-56 flat head stainless steel screws to hold the LCD in place. I will have to use some kind of glue or silicon to hold the window onto the case. I also placed an insulating piece of plastic at each end to provide support for the nuts rather than have the nuts come in contact directly with the LCD PC board. Any ideas about what to use to attach the window to the case?
  4. Trim and Channel 6 and 7 Control Pots: The best trim and control pots are the ones that are no longer made by Bourns that had the 1/8” shaft with the lock nut that could be adjusted to place drag on the shaft to hold the setting. I placed a small but very stiff compression spring on the pot shaft between the pot and the pot mount to apply drag. It feels OK but a better way might be available if some of you put your thinking caps on. For the rudder trim and channel 6 and 7 controls I used plastic units I scavenged from some of the eBay parts transmitters I bought. I took them apart to clean and lubricate them with some Ace pot lubricant I still had. The wafers and wipers looked very good probably because they are not cycled as much as the primary controls.
  5. Restoring the Case: I had to fill a bunch of drilled holes and slots that were in the case. I filed a bevel on both sides of the slots and slightly countersunk both sides of the holes so that the epoxy filler would not fall out if the bond ever failed. I attempted to duplicate the bumpy surface of the surrounding vinyl by cutting a piece of another old transmitter case and clamping it to the case. I placed the epoxy from the inside just enough to fill the opening. Unfortunately, the epoxy ran out from under the clamped piece of old case and it would not come off. I had to very carefully sand off the excess and then file down the excess from the inside of the case until it was flush. What worked better was to back up the holes with a piece of masking tape. The tape prevented the epoxy from spreading out onto the outer vinyl surface but it did not provide the bumpy surface I was trying to achieve. I tried to get a bumpy finish with the vinyl spray color I used but it flowed out smoothly. These spots are not easy to find but if you look closely at some of the pictures I sent in you will spot them.
  6. Finishing the case: I used a vinyl spray from a company called SEM I bought at an automobile paint supply store. It comes in a wide variety of colors. I tested it by applying fuel to it; it is fuel resistant. I used stainless steel 2-56 and 4-40 machine screws I bought from a company called SMALL PARTS INC. Check them out. The screws and nuts I bought in packages of 25 were dirt cheap compared to buying screws from a hobby shop for a couple of bucks for four. I used the flat head screws rather than the typical pan head screws because it looks so much better with all the screw heads flush with the exterior of the case.
  7. Switches: If you look at the recent pictures I sent in you will see that I reduced the length of the toggles on all the toggle switches because I am very concerned that I might accidently hit one unintentionally while flying. It makes them harder to flip but that is what I wanted. I used a Noble switch from another parts transmitter for the Run/Cal switch, rather than a locking SPDT toggle switch because I had an extra and I like the way it looked behind the antenna mount. In the Cal position the switch cover is held open by the pin in the cover. It is easy to tell if the switch is in the Cal or Run position.
  8. The Gimbal: At first I was going to use the World Engines Expert 3 axis plastic gimbal from my old WE transmitter but I damaged the rudder knob trying to get the knob apart to replace the pot wafer. It is one of the best plastic gimbals because the rudder knob is so good and the plastic is fiberglass filled and very stiff. It uses the ½” pot wafers which are as rare as hen’s teeth. Next I was going to use a Kraft 3 axis gimbal I bought on eBay but it had strange pot resistance values. I did, however, scavenge the rudder knob as a spare for my Silver Seven. Next I came across a Royal Omega two stick transmitter with Ace look alike metal gimbals and proceeded to fabricate a hollow stick to hold the Kraft rudder knob, but then Kees dropped a note to us that he found Bourns 6639 pots that have some very good qualities, among which are very smooth feel, low turning torque and extraordinary long life. I bough two to use in the Omega gimbal. Then I found the Proline gimbal that I fitted with some more Bourns 6639 pots on all three axes. It was a tight fit but the rudder pot just fits inside the case without shorting out the pins that stick out the back of the pot. I also made new centering scissors with long spring arms so I could adjust the tension by moving the springs in or out. The sheet metal frame of the gimbal allowed me to mount the aileron and elevator trim pots to it. The one thing I revised was the outer pivot because the stock pivot caused binding. I made a new pivot from a ¼” turned down brass screw that fit precisely in the nylon bushing, but had to float the pivot pin and nuts and washers on epoxy so that the pivot pin lined up exactly with the axis of the elevator pot shaft. The elevator pot held the assembly in alignment while the epoxy hardened. Smooth as silk.
  9. RF Deck: I used the XPS Proffi 4000 RF deck because it is available without the plastic case because I wanted to mount the deck totally inside the transmitter. Access to the bind and program button and view of the LED is through a small hinged hatch. The hinge came from an old Super 8 movie camera and the latch is a miniature hatch latch made by DuBro.


I know that this is a very long post but I hope that some of the trials and tribulations I went through will help those of you building or contemplating building a Microstar 2000 transmitter. If any of this raises questions let me know. I will try to answer all of them. Yes, I now have two metal gimbals, one fitted with Bourns 6639 pots and a Kraft rudder knob with a new CTS cermet pot wafer that I am holding for a spare for my other Ace Silver Seven.

Tony Staten Island.