Ham Radio - Salvaging a burned MFJ 962D versa tuner

Getting this poor thing working again.

Hit me up on the echolink repeater down by my house: W9TE (Node: 519521)

[larryjohnson]

Once again, I have now learned something important. I have learned how to tune my radio with a manual tuner. My friend kinda showed me how, but he was close, and you reinforced what I had been doing already. Great job. You can teach an old dog (me) new tricks.

[Barracuda]

Air dried tooth paste or brasso polish cream and this brush for course cleaning and cotton tips for spot cleaning . The poor ham use corn oil drips in baking soda

[MujoNovak]

what a shit, they should pack a toothbrush inside the packege as standard. I hate that I am a MFJ owner. Made in USA but worse asembly than china in my case MFJ 945E.

[TheRangerDale]

Very good Kevin good move yes I would have done the same on the repair. And yes seems lot of that type of tuner same problem about, But Ebay Sales and buyers, never know on some cases, more and more sales quote NO returns as to Part changers and damage users..well explain and thanks for the effort made Kevin 73's dale

[jonthebru]

Very informative, I'm looking at buying the 300 watt version second hand, I think it may be wiser to buy a new one after watching your video.

[jimself]

Nice video, Kevin. I am working on one, too. 989C. This is helpful information. Hope you are doing OK. Still in Indiana?

[geeess]

MFJ manual: "Understanding power ratings. There are no standardized power rating systems for tuners. The names used (i.e. 3 kW Tuner) carry over from the time when amplifiers were rated by peak power input, and not the true RF power output... The FCC has changed the power rating system of amplifiers, and tuners no longer follow amplifier power ratings." Whatever, right? That burned switch thing you removed often gets stuck slightly off contact.The MFJ-969 has a lot of arcing problems.Tuner still works but slightly erratic at certain spots until it totally carbonizes.

[georgescaruana]

JE VIENS DE FAIRE L'ACQUISITION d'une MFJ -969  Deluxe versa tuner II je ne maitrise pas tout a fait son fonctionnement sur ttes les gammes ...à bientôt  mais c'est une "chouette" boite d'accord . 73 F8FSN

[kbvsb]

Thank you I have the same Tuner and it did the very same thing. Lesson learned .Do NOT hook up a Galaxy radio to your MFJ 962D Tuner. I blame the Radio. All kinds of Spurious and deadly emissions! I am Glad however that it isn't a total loss. With a clean up, good Coax, good Coax length and antenna; A good signal will get out much better than high wattage!

[biringen]

Did you think of modify it from T match to a S match?

[BruceNitroxpro]

I just couldn't take it any longer... around the 13:00 min. point, all I could ask was... WHAT? Have you ever heard of replacement parts? Not sure, even though I have two MFJ tuners, but MOST companies can make money selling replacement parts on almost all models of this gear. To not even MENTION this seems weird. de KQ2E

[walterslover]

I talked to Robert at MFJ Tech Service, here is what he said about the "Self-Resonance Killer™" (MFJ Registered Trademark).

Robert, MFJ Tech:
The “Self-Resonance Killer'' on the MFJ-989C is a device that at times aids in tuning on some bands. It's not necessary to have, old tuner didn't have it. They worked fine.

[sincerelyyours]

Nice repair. I bought a similar tuner off eBay, the MFJ-969 (300 Watt version), for what I thought was a bargain, but it, too needed some work to get properly operational. Mine wasn't burned but its anti-self-oscillation switch was jammed and would not allow the roller to advance beyond it towards the rear of the coil. Seems the hex shaft and associated switch were positioned 1/16" too far forward so the fiberglass parts would strike the coil and not enter it between the windings as they should. I found that the shaft was just missing its rear-most circlip located just behind the coil assembly. Replacing the circlip (actually an "e-clip") and adjusting the switch's copper contact slightly fixed it and now the switch assembly works perfectly. I also found that the roller's forward and rear end stops were off just enough to make the roller stop hard on its sharp edge at the extreme edges of travel instead of on its side axle as it should. While this didn't affect the tuning in any way, it would have eventually caused a ding to form in the roller's edge so slight adjustments to the stops with a file were needed to make to make them work properly. That required removing the coil assembly from the case but that's not overly difficult. While it was out I also oiled the shaft bushings so now it turns quite smoothly.

[davidj.wilcox]

I have a similar tuner, but for lower power. Your fix is just a reminder for MFJ owners and others that the roller contact wheel needs cleaning at least once a year (whenever the receive audio gets scratchy while tuning). I use a can of old TV tuner cleaner.

Dave K8WPE

[markanderson]

I enjoy the videos Kevin - thanks. But for that part, yes you could have tried to fab from scratch, possibly on your new 3D printer :) but - why not just buy a replacement part from MFJ - assuming it's sold/available as a replacement part.

The function is to short out that section of the coil so that it's inductance with its own self capacitance, does not become resonant. Have to know what that capacitance might be to know if it's truly a concern or not. If the part was not ridiculously priced, probably better to restore back to original design... IMHO as they say 73 WB2SMK

[vavad]

I have the MFJ 989C version rated 3 KW
It is interesting the coil size is the same as the 1.5 KW tuner.
Many Ham Radio operators have the same problem at the same spot.
My tuner was smoking right at the white insulator in the middle by the magique switch.
I noticed some metallic shaving was present on the insulator and shorted out the wheel.
It was smoking with only 500 watts.
I removed the magique switch, cleaned up 3 years ago and no issues any more.
73 VA3VAD

[Steve-GMHUU]

Thanks for the video Kevin.
I think I have came across similar coil "self-resonance killers" before. Guessing that MFJ must have found the unused coil tended to resonate around at least one frequency within the operating range. (maybe at higher power levels??).

My old roller inductor matcher sounds a little scratchy these days. Think I will try your contact cleaner trick.

[johncliff]

Hi there Kevin, Good point about puting power through the tuner while rotating the roler mechanisum. I nev had the chance to look inside the ATU for the C11/R210 that was my bread and butter radio when I was a radio opperator R.Signals years ago. We used to spin the cranking handle round at a fair old rate to tune the inductor, then just a quick tweak on the cap to show max out. If the box was anything to go on what the internal components were like. They must have been prety substancial. The box was cast Ali, about 5 1/16" thick. It would have been 14"x7"x5". It was mounted as solid as a rock onto the top carring tray, next to the R210 Rx. The whole set-up was supposed to be portable, carried by a mule. Poor soding animal. Along with a pair of 12volt, 75 AHC Batteries. It would be enough to criple the mule. 73 de John- Aka G0WXU

[j.d.schultzsr.]

Excellent video for you solid state folks. I was first licensed in 62, and I learned to tune up tube equipment without any outboard tuner. After I fried a few pair of 6LQ6s, I learned to tune to the noise floor first. Boat anchors are much easier matched (than solid state) to a properly cut wire antenna, but you still have to be close.
My ARC5 XMTR has a roller inductor inside, for tuning (with the magic eye) to a ZEPP dragged behind a B17/B24.
TNX FER INFO 73 W8IMP AR SK

[chrisandkristin]

Old vid. But I took that anti-resonator bar out of my 962D when it was new. That thing is a known problem. I've run the tuner behind an AL-811 for years and never had a problem with whatever that bar is supposed to do.