The Big Twitch!
The first thing you should know about troubleshooting the Big Twitch is that I will help you if you don’t find the problem. And, as all of us recognize, it is impossible to fix something if you don’t know what is wrong. Problems often show up as symptoms in a part that is not the problem. So don’t jump to conclusions.
Glitching, searching, whatever you want to call it, is not serious, and easy to fix.
A servo that shakes back and forth, or twitches without explanation.
The conversion from electrical energy to physical energy takes place in a part of the system called a potentiometer (pot for short). The symptom is usually the result of dirt in the pot. In this case, dirt can be a microscopic spec of dust or miniscule drop of moisture.
Please note: If your transmitter is inside the house, or is held closer than 15 feet from the boat, a signal feedback can cause servos to twitch. So make sure to test for this problem with the transmitter at least 15 feet from the boat.
There are four pots in your two channel electrical system. One in each servo, and two in the transmitter (one for each channel).
First of all, steering servos are the most vulnerable to twitching. So we will start there first. But troubleshooting for a twitchy sail servo is just the same.
- Remove the receiver (under port deck on velcro) so that you have it above decks where you can see it well. On the receiver (also called a battery eliminator circuit), you will find three plugs in the side. One reads “bat”, and the others say Ch 1, and Ch 2. Into these receptacles are plugged the two servos (3-wire plugs), and the lead from the switch/battery (2-wire). The black wire of all three plugs should always be to the right as you read the writing on the receiver.
- Ch 1 is usually the steering servo, and Ch 2 is the sail control servo. This first test is to determine whether the twitching is the cause of the transmitter pot, or the servo pot. Switch the two servo plugs in the receiver, so that they are plugged into the opposite channel.
- IF the twitching stays with the servo, then you know the pot that is dirty is in that servo. If the twitching moves to the other servo, then you know that the culprit is the pot in the transmitter that controls that channel.
Once you know which pot is the problem, the fix is not difficult. You will need to open the device that contains the dirty pot. Note: Dirt in the pot is not considered a warranty issue because it is not a fault in manufacture or material.
If the transmitter is the culprit, do this:
The transmitter has 5 screws on the back – remove and open the case. Go to the control that is giving the problem, and find a small round housing. In the end of this housing you should find a small hole. Spray a non residue contact cleaner in the hole (find at a stereo store or Radio Shack). After spraying, exercise the stick back and forth, with the power on. The problem should clear itself.
If the servo is the culprit, do this:
The servo has 4 screws on the bottom. When you remove these screws, be very careful to remove the bottom section, leaving the top section (gear housing) in tact. Remove the circuit board from the bottom and find the small round housing as above and treat it the same.
These symptoms can return. Sometimes it is dust remaining in the case from manufacturer, or you sail in a humid atmosphere (like on the water). Once you fix the problem, you will no longer fear the unknown. Sometimes, continued exercise of the affected channel will clear the “dirt”. Other times, you will need to “operate”.
This article was written by Steve Lang of SailRC.com.