Its been an interesting couple of days here in the Zed Man’s shack. For starters, several nights ago, I attempted to change the inductor setting on my beloved MFJ-986 Differential T antenna tuner; when I cranked the inductor knob, the turns counter didn’t move.
WTF??
Yeah, I knew what it was. It was the early Rube Goldberg designs used on several of MFJ’s early antenna tuners that had adjustable inductors.
Per the photo, you can see that the pulleys mounted on the inductor shaft and the turns counter are connected with a very thin rubber belt, which basically is an “o” ring. The belt has moderate tension on it, and despite its Mickey Mouse design, actually works reasonablly well at keeping the inductor tracked as you tune it. Unfortunately, time and the elements catch up eventually with those thin rubber belts, and they break — which leaves me where I was in this week.
I have become a very big fan of the Differential T style tuner, and over time, I’ve purchased three of them (if one spare is good, two spares is better!). With my main tuner down, I went to the attic to seek backup tuner 1.
My original MFJ-986 has the old style black front panel, and black case. Backup No. 1 was the same age tuner, and unfortunately, it suffered the exact same problem — the rubber belt connecting the turns counter to the inductor shaft was broken. ARRGH!
Backup MFJ-986 No. 2 is a more recent version of the tuner with the brown front panel. On later MFJ tuners, they (finally) replaced the rubber belt with nylon gears to connect the inductor shaft with the turns counter — a substantial engineering upgrade! I put that tuner in place, and found the tuner’s metering was completely dead. No power indicated, forward or backward. Bummer.
So with the tuner in place, and two offline, I decided to look for replacement O rings for the two tuners. My first stop? The car parts store.
I knew better than go to one of the national chain stores. Those kids only know how to find parts when they have the year, make, and model of your car. I needed a good parts counterman.
I found him at Tatum Auto Supply. I showed him my original broken-but-taped-together O-ring, and asked him to find a suitable replacement. He disappeared to the back, down a maze of narrow aisles stacked high with thousands of boxes of parts.
He returned a little while later with a single O-ring — it was a good match for the one I brought in, just a little thicker. I prepared to tell him I wanted 3 of them but in mid-sentence he injected, “This is the only one I have.”
In fact, he couldn’t tell me what his O-ring was supposed to fit. He just found it back in a drawer in the back. No part number, no price, no nothing. No idea how to find another one. When I asked him “how much,” he handed it to me across the counter. “Take it.”
The new O-ring worked and I installed it. Then I wondered if I could use a thin, similar-sized rubber band as a belt. I found some suitable rubber bands in our desk drawer, and found one that worked.
I’ll probably call MFJ and order two replacement belts if they’re available. Just in case, lol.
SMOKING IN THE RADIO ROOM. I changed up the operating position when I had to address the antenna tuner problem. The tuner was on the bottom of a stack of three pieces of gear; it was beneath a Kenwood TS-530S and the Drake PS-7 power supply. I took the Kenwood off the operating desk and placed the PS-7 on the desktop, put the Drake TR-7 on top of that, and put the MFJ-986 on top of that.
Of course, the operating table was a mass of keys, paddles, and cables normally, and all these changes increased the cable chaos by a factor of 10. While tuning around on 10 meters, I heard the power supply grunt a deep GRRRRRRRRR. WTF?
In seconds, smoke filled the shack; both wires of a small two-conductor cable were glowing red hot, the insulation drippiing off the wires onto other cabling. Instinctively, I grabbed the red hot cables, though I didn’t hold it long. I realized it problem was a direct short to ground, so I quickly shut off the main DC supply and let the smoke clear and the wiring cool.
One of MFJ’s early design flaws on some of their keyers was the use of a two-conductor mini-phone jack to provide 12vdc. The problem was that when you plug the power to the keyer, you have a momentarily short. There’s no way to plug the power in without a momentarly short. Anyway, a DC cable I created months ago was still laying on the desk under a pile of other cables. I’m not sure what I did, but that connector shorted to ground.
I use an MFJ-1118 DC power distribution strip in the shack, and one of the “upgrades” I made was to replace the wimpy ass 15 amp fuse for the switched outlets to 40 amps. The fuse is inside the strip and that makes it a pain in the ass to replace; raising the fuse rating meant you could have a momentary short and not blow a fuse. I was a little surprised my “momentary short” failed to trip the fuses in the DC strip. Maybe the small diameter of the wiring limited the current draw.
QRP AND ME. I’ve written here before about how much fun I’ve had with the Xiegu 6100 HF radio. Connected to 13.8 VDC, the radio transmits 10 watts. It really is a nice, very compact QRP radio. I wish it had bandstacking registers like my PROII.
While rooting around the shack I located my older QRP rig, a Chinese made mcHF transceiver. The rig has advanced features including DSP, but is limited on transmit to 5 watts. I used it a couple of nights to check in to my Georgia CW traffic net, and it did an admirable job. Tonight I used my IC-756PROII.
RETURN OF TEN-TEC. My original shack layout changes included moving the Ten-Tec Omni V+ back to the operating position. That radio is wider than the Icom, Drake of the Tempo 2020, and it just wasn’t going to look right.
I decided I need to move some junk out of the way and open up the right end of the table. It will give me room for the Ten-Tec and another radio or two. I also have my Yaesu FTDX-3000 I’m not using now, and it deserves a place on the operating position.
73 ES CUL ….. de KY4Z SK SK (dit dit) …