The 3TXA, 3TXB and 17TN fobs all suffer from common faults that will render a once working unit inoperable or with intermittent operation.
The 3 circuit boards are similar, the 17TN fob has a more robust design and is the less troublesome of the 3.
Here are the 3 circuit boards....
The most common fault is to do with the battery holder and how it is soldered to the circuit board. There are 3 legs and they are soldered on both sides of the board, various sections of the circuit take power from different legs, thus all six joints need to be properly soldered.
If the legs need to be resoldered remove the battery and press the holder towards the board while soldering, this ensure that the battery is held tightly and makes good contact.
Here are some pictures of "dry jointed" legs and will give you a good idea of what to look for...
The 3TXA and 3TXB fobs use a canister type crystal for the clock signal, ideally this should be glued to the circuit board but it is only held in place by it's two wire leads. It's common for the wire to fracture where it has been soldered to the board.
Sometimes the two tact switches can fail on very old fobs, they can be replaced with new items. Generally though the soldering fails and one or more of the switch "legs" becomes dry jointed...
The 3 circuit boards are similar, the 17TN fob has a more robust design and is the less troublesome of the 3.
Here are the 3 circuit boards....
The most common fault is to do with the battery holder and how it is soldered to the circuit board. There are 3 legs and they are soldered on both sides of the board, various sections of the circuit take power from different legs, thus all six joints need to be properly soldered.
If the legs need to be resoldered remove the battery and press the holder towards the board while soldering, this ensure that the battery is held tightly and makes good contact.
Here are some pictures of "dry jointed" legs and will give you a good idea of what to look for...
The 3TXA and 3TXB fobs use a canister type crystal for the clock signal, ideally this should be glued to the circuit board but it is only held in place by it's two wire leads. It's common for the wire to fracture where it has been soldered to the board.
Sometimes the two tact switches can fail on very old fobs, they can be replaced with new items. Generally though the soldering fails and one or more of the switch "legs" becomes dry jointed...