After a long break in the 1990s, in the early 2000s I decided to return to amateur radio. Unfortunately, room availòability and roof access issues prevented me from using my trusty Kenwood TS-830M, which I bought when I was 15 or 16 with my life savings. So I decided to buy a so-called "quad-band" transceiver, a transceiver that covered all MF and HF bands, VHF (50 MHz and 144 MHz), and UHF (430 MHz). I then purchased a second-hand YAESU FT-100D from a well known shop in Asti (Italy), that many of us, Italian radioamateurs, are undoubtedly familiar with. It's a very comfortable radio to use, still valid today, with a few flaws, it's true, but also many advantages. Over the years, some problems have arisen, common to all devices of this type, including a problem with the optical encoder that controls the VFO. It happened that, when continuously rotating the VFO knob, the frequency would vary somewhat in spurts, that is, regularly for most of a complete rotation, then it would lock on one frequency and then resume varying normally. To solve this problem, the simplest thing to do is to replace the VFO's optical encoder, which I found to be a fairly simple operation, certainly within the reach of many radio amateurs with some familiarity with mechanical assemblies. This doesn't require extensive electronics knowledge, as long as you know how to unplug, and plug in back, a connector.
Required Materials
First, we need the spare part. I purchased it a long time ago from the Italian distributor of the Yaesu brand because it was easy for me to quickly get one for another purchase, but you can also buy it from any electronics component distributor. The price is more or less the same, just under thirty euros, if I remember correctly. Be aware that the model you purchase from a generic distributor may not have the connector pre-installed; if you're unable to find and install the connector yourself, buy the official Yaesu spare part, which, as I said, won't cost much more.
The encoder you need is this: COPAL RES20D50-201-1D (instead of COPAL, you might find the NIDAL brand; don't worry, it's the same thing). These encoders were originally made in Japan, but production recently moved to Vietnam.
That's all there is to it with the spare parts. As for the tools, you'll need a Phillips screwdriver. Hear ye hear ye: you don't need a soldering iron!
Recommendation
Hey, I know that when I start with recommendations, I'm as annoying as my old Aunt Rita; read them, don't read them, do what you want, just as long as if something bad happens to your radio, you don't come whining to me... When working on electronic boards, or even just getting within a few inches of them, you must wear primary electrostatic discharge protection, namely the infamous ESD wristband, which must be connected to electrical ground via a power resistor with a resistance between 1 MΩ and 2 MΩ. Furthermore, the surface you're working on must also be "ESD safe," meaning at least static-dissipative, and connected to electrical ground in the same way as the wristband. Finally, the surface should be smooth and soft so as not to scratch or damage the object you're repairing. In short, if you don't already have one, buy an ESD wristband and an ESD mat and connect them to the electrical ground. The resistor should already be included in the kit you purchase. Remember to wear the bracelet properly (the metal part in contact with the skin on your wrist) and always; don't be like me and put it aside at the first opportunity and then forget about it...
Caution: ESD-induced failures aren't always destructive; they often only cause "soft failures," failures that appear sporadically and under certain operating conditions, such as when the DX you've been waiting for your whole life calls your callsign. Again, don't panic: you'll certainly have another chance to connect that ATNO1 in another thirty years, plenty of time to even buy an ESD protection kit in China.
Step-by-step instructions
If I've done everything right when publishing this article, there should be a video, somewhere here below, explaining the steps required for the repair. (Edit: Yes, I did it, it's at the end of the page...)
- Remove the faceplate from the radio as usual.
- We need to remove the soft ring (rubber or something similar) from the VFO knob. I lifted it slightly with a plastic screwdriver and then, pulling this way and that, in a couple of minutes I was able to remove it from its support. In the video I remove it in a flash, but don't trust me; there's a trick.
- On the side of the knob, you can now see a hole containing the grub screw that secures the knob to the encoder shaft. Loosen the grub screw enough to easily slide the knob off the shaft.
- Contrary to what was described in the tutorial I referenced, it's not necessary to remove the other knobs from the radio's faceplate. I didn't know this yet, so in the video, you can see me removing them. Save yourself the trouble.
- Unscrew the screws on the back panel of the front panel and open it. You can disconnect the connector for the wires that lead to the contacts between the front panel and the radio, allowing you to work more freely.
- We can gently pull on the small connector mounted on the encoder wires.
- To remove the encoder from its housing, we'll first need to remove the nuts and washers from the shaft. It's not difficult, but it might be helpful to take a photograph of the assembly so we can replicate it during reassembly. Before removing the encoder completely, note its original orientation in its housing. The recess is D-shaped, so the new encoder will only have one mounting position.
- Now, let's place the replacement encoder in its housing, paying attention to its orientation, install the threaded ring, and put all the assembly pieces back in place.
- Connect the encoder connector and the connector on the front panel's rear panel to the front panel's circuit board.
- Close the rear panel, tightening the screws without applying excessive force.
- At this point, if you have any doubts, you can temporarily replace the faceplate on the radio, turn it on, and verify that the new encoder works. Then turn the radio off, remove the faceplate, and continue with the assembly.
- Mount the knob onto the encoder shaft and tighten the locking screw.
- Replace the rubber ring on the VFO knob.
- Congratulations! You're finished, and the VFO works like new.
I really hope this tutorial is helpful, and I'd love to hear from you to let me know if everything went well or if I need to clarify anything in the tutorial.
Notes
1 ATNO, acronym for "All Times New One," is a DXCC entity connected for the first time.
References
M0YKS, FT-100 VFO Rotary Encoder Replacement, September 29, 2007
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