MFJ Deluxe Versa Tuner II O-Ring Turns Counter drive belt

Discussion in 'Radio Circuits, Repair & Performance' started by WQ6N, Aug 10, 2020.

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  1. WQ6N

    WQ6N Ham Member QRZ Page

    I have a very nice MFJ Deluxe Versa Tuner II that I use RV mobile. The turns counter is a O-Ring drive belt which just broke. Current TC is a 3:1 ratio. Reaching out to MFJ they suggested the mechanical TC-11 TC. This counter has a fairly large rectangle zero reset button that required enlarging the pin push hole of the O-Ring TC. After I did this, the gear was still 3/16 too high from the inductor coil shaft gear they provided. One cannot raise
    the inductor due to the drilled faceplate. There is a possibility to lower the turns counter but that would require enlarging the TC window. Didn't want to compromise the faceplate any further so reached back to MFJ and they said that they will send me another TC.
    This time, I received a beautiful TC-12 with a 5 digit read out. Talk about fine tuning. Much to my dismay, there is not enough real estate on the Versa Tuner front panel to mount this TC. So back it went with the TC-11.
    I have asked MFJ to send me replacement O-Ring drive belts and that will have to do. I will take OD and thickness measurements and will post.
    Everything is possible to mount the TC-11 but it would require more front panel modification than what I wanted to deal with. Hope this lesson learned will help some one else. I would also like to note that it was not difficult to remove the tuner front panel which is needed to replace the O-Ring or gearing. In fact, the roller inductor just has to be loosened and not completely removed as suggested in other threads. Cleaning the roller contacts is highly suggested though.
    Since the ratio is 3:1 its not hard to get into the ball park on the roller inductor. I just use the old school method of listing for the highest audio signal and fine turn from there. A broken TC drive belt is certainly not a deal breaker.
    KA9JLM likes this.
  2. K9YLI

    K9YLI Ham Member QRZ Page

    If the O ring is small, less than 3 or 4 inches diameter, go to a big hardware store and buy a new O ring. If its a longer belt , then digi-key and mouser have all kinds of belts for tape decks etc. round and square and many diameter and lengths.
  3. WQ6N

    WQ6N Ham Member QRZ Page

    I found the broken O-Ring. Doing the math, it looks like 2-3/8in OD with a 1/16in CS.
    I would bet that a 2-3/8in OD with a 3/32in CS would work fine
  4. N6UH

    N6UH Ham Member QRZ Page

    I superglued mine back far so good!
  5. WQ6N

    WQ6N Ham Member QRZ Page

    Well superglue is kinda interesting... I did get the new belts in from MFJ, great service. and they measure more like 2-1/4in OD with a CS of 1/16in.
    In any case the Turns Counter is working. I did add a couple of spares just in case that are sealed and inside the tuner for safe keeping.
    I had full intention of cleaning the roller inductor with isopropyl alcohol . There is no way to do this without taking it all apart.
    So I gave it a bath with the alcohol instead and wiped down with a microfiber towel. I can finally say the tuner is back in business. It will go back into the pelican Go Box waiting for the next RV adventure.

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