As I mentioned back in December, I’m now finally using the MFJ 941D VersaTuner II antenna tuner I bought many moons ago. At the time, I also noted that the metering wasn’t working. In no switch position, could I get the meter to move at all.
Well, about a week ago, I began to notice that every once in a while the meter would indicate some forward power. This activity usually lasted for only a single transmission, and on the following transmission, I’d again get nothing. Problems like this are usually just bad connections, so having a little time on my hands yesterday, I decided to pull off the cover and see if I could find the bad connection.
The first thing I noticed is that it would be an awful lot of work to actually get at the connections, much less replace a component. The circuit board with the switching and metering circuit is mounted on four standoffs to the bottom of the box, and all of the traces are on the bottom of the board. To get at those traces, I would, at minimum, have to unsolder the wires connected to the meter and remove the knobs from two of the front panel controls. Then I might be able to swing it up so that I could get at the bottom of the board, but that would still be difficult because of all the wires that run to the board from the coax connectors on the back panel and the coil and capacitors of the tuning circuit.
While I was mullling this over, I did a visual inspection of all the connections I could see. They all seemed to be good solder joints, so I rule them out as the problem. One thing I did notice is that one of the capacitors was mounted very poorly. One leg of the capacitor went straight down into one hole, while the other leg was bent. couldn’t see the lead on the straight leg, making me think that this may be the bad connection. Perhaps the coating on the leg prevented a good solder joint to that leg. While it may have made a tenuous connection at first, the shock and vibration experience by the tuner while in use and through several moves finally caused that connection to come loose.
Since I really didn’t want to hassle with disassembling the whole thing just to get at the board, I decided to wiggle all of the components to see if I was right about the loose connection. What do you know? It worked! Now, the meter is reading as it should. That is to say, it swings up when I transmit and the switches are set to read forward power. I have no idea, of course, how well calibrated the meter is. I suspect that it’s not all that accurate.
Since what I did was kind of kludgey, I expect that the meter will quit working again soon. At that point, I really will have to take the thing apart and resolder the connections. Uggggh.
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