#214

repair and testing.

[@jeffminnick5209]

While I can appreciate MFJs commitment to the ham community, they are all to well known for "the occasional issue"...Peter, as usual your work is impeccable and it makes my day to see your videos Stay well and 73 Jeff de WD8JM

[@TRXLab]

You are right Jeff the commitment to the ham community is a good point in those times we ling in. Thanks for watching

[@Standing-Wave]

Great video!!!! As usual. MFJ is definitely a brand for those who aren't afraid to tinker. I don't believe they have a quality control department at all. I've taken apart more then a few MFJ pieces that where covered in flux or had cold solder joints, over soldered joints, solder bridges, and sometimes just totally missing parts.

[@TRXLab]

Thanks for watching

[@majorrhys9729]

instaBlaster.

[@enigmarbs2886]

Very interesting video, Peter! I again learned a lot from your repair job... Peter, you are brilliant... Thanks for teaching us all this stuff 👍🏻

[@TRXLab]

Thanks for feed back

[@DonJones-ui2cn]

The author drags out a simple repair until I could not stand to listen any longer. Remove the freaking soldier bridge! GEZZ!

[@johnathanasiou9284]

Great video Peter, appreciate you sharing the thought processes behind it all. Rather watch your quality & informative videos than most broadcast TV these days. Keep up the awesome work!

[@TRXLab]

Thanks for feed back very much appreciated..

[@ot7e]

Great video Peter and thanks for teaching us all this stuff. I remember having an MFJ ATU here 15 years ago, one of the coils was mounted to close to the metallic enclosure were it shorted!

[@TRXLab]

oh not good

[@johntheglass]

an excellent piece of logical deduction( electronic engineering), my 994brt works just fine but tempted to break the seals to inspect the inductors in the bias T. great work

[@TRXLab]

Thank you!

[@masterfranco01]

Great work Peter, and as always a great ham teacher. Thanks.

[@TRXLab]

Thank you

[@bblod4896]

I built a small AM receiver but could not find the needed inductors so I purchased magnet wire and rolled my own. Worked great. Thanks for the video Peter.

[@TRXLab]

of curse that always work as long the resistance is low enough...

[@80Loke]

Always great when you upload a new video, thanks:)

[@TRXLab]

Thank you

[@K33n3]

Another Brilliant Video, I learn something every time!

[@TRXLab]

Thank you

[@paulcollins9839]

Always a pleasure to see your work and your thought processes Peter. Paul de M0BSW

[@TRXLab]

Thank you Paul

[@chrispeters7520]

Brilliant as always!

[@ne2i]

I have the 998 rt and its been back to MFJ once. It works fine now. It's a very versatile tuner. I have the OG SGC and modded it to be able to use bias tee's. pretty easy.

[@w.rustylane5650]

I've got a MFJ 969 Versa Tuner II wit a roller inductor. However, it's only 300 watts. That tuner will tune anything including a bed spring. It even has an internal balun of 4:1 including a dummy load. I really like this tuner. Most all of my antennae are resonate so I don't really need an external tuner. The tuner in my Yaesu 991a will tune all my antennae. Sure do enjoy your videos. W Rusty Lane K9POW in eastern Tennessee

[@rfmonkey4942]

thank you for taking the time to do these videos, ja wunderbar. regards from VK3

[@TRXLab]

thanks for watching

[@earlrichardet2102]

Wow, great work Peter. I thought you may have found the issue when you found the ground in the wrong place, but then to find that the coils were the real issue. Nice trouble shooting!

[@TRXLab]

yeah it is always an exiting journey

[@alexfra77]

Very interesting Video! My Tuner (brandnew) does not have the described problem. Works like it should.

[@eddycuypers7621]

Thanks. Very interesting. So much for MFJ's quality control. for a tuner that is sold for about 459 Euros.

[@Dratchev241]

well they call it mighty fine junk for a reason

[@frankjankovich3512]

Another example of Mighty Fine Junk (MFJ)😀

[@billnicholson2470]

You are quite the detective Peter. Very nice informative video. Thanks de kb7ici

[@TRXLab]

Thank you

[@jurgentraude7669]

Nice job Peter!!!

[@TRXLab]

Thank you

[@r.f.lab-renefilho1453]

Nice job Peter ! Gongrats for great solution !... 73's

[@TRXLab]

Thank you

[@JamesP6084]

MFJ Made From Junk, I had a MFJ 100W tuner that I had to change variable capacitor so it would not arc at 10W capacitor plates way too close, Thank you Pete :-)

[@M0UAW_IO83]

Hmm, I've seen a similar fault, I think perhaps the short pulled too much current through the inductor and cooked off the lacquer inside, making it shorted turns.

[@bbrand6755]

Yes, if the center pins of the switch were grounded then any DC input voltage would haven been directly shorted to ground via the two inductors. They wouldn't have survived that for long.

[@TRXLab]

That the inductor might have cooked is a good theories

[@tiggydorset9041]

My guess was that the dodgy switch wiring was someone elses poor attempt to fix/get around the inductor problem which they obviously missed.

[@AlGritzmacher]

I also had a MFJ-4117 where the inductor burnt up. Those bobbin style inductors have very fine wire and when they overheat turns short out. I replaced the inductor with JW Miller unit that had much larger wire, yet was not much larger, and fixed the problem.

[@thuff3207]

Awesome as always. Thank you for sharing.

[@TRXLab]

Thank you

[@Manawyrm]

Great video! Thanks for uploading :)

[@TRXLab]

Danke Tobias

[@R2AUK]

Thanks for the video. I would suggest to keep some ferrite cores for cases like this one. The ferrite choke you needed could be wound on FT114-43 core, 22+ turns of 0.9 mm enameled wire would do the job. 73s de R2AUK

[@TRXLab]

That would be around 450uH and should work as long the wire resistor is still in the mOhms...

[@M0UOO]

Great video I have had one of these since they were released, the original one were even worse. No pcb board just three capacitors and the fibreglass box nevered sealed very. Mine is sat under the bench. 73 Richard M0UOO

[@TRXLab]

thanks for feed back

[@stony7827]

as usual --- a very good Video, many thanks(!)

[@TRXLab]

Thank you

[@enzobisconti8089]

Well Done!!!!

[@davidwalle5025]

MFJ - Mighty Fine Junk, Mississippi Finest Junk. Great Video. MFJ usually makes ok equipment but not this time. Keep the videos coming.

[@TRXLab]

Thanks for watching

[@WallDiver7]

Great Video..... very instructional!! Thank you! Have you found a way to change the factory default "Target SWR" ? The 998BRT has a mode button to accomplish this, but the 993BRT and 994BRT do not.......... it was never installed!

[@iw0hex]

Great job Peter. 73s Pasquale IW0HEX

[@TRXLab]

Thank you Pasquale!

[@KD0CAC]

Could questions in my mind , the markings on the original chokes - if they may have been correct - but then shorted out & changed values - by the on/off SW. ? My quess that that small wire grounding the SW. may have been solder left by the worker installing the SW. , and it soldered to the ground plain - then when RF power applied - shorted the chokes - changing the values ? Thanks again John

[@stargazer7644]

That side of the switch was intentionally grounded. The PCB was wired so that the switch applies power when on, and ground when off. The weird wire/solder line wasn't doing anything. The problem was the wrong value inductors were used, and the unit was never tested.

[@BobMellor1954]

Thanks Peter, I wonder how many more of these units were sold with incorrect inductance values; great video

[@TRXLab]

Thanks Bob. Yes that is a good question but it might be it was an operator error....not so sure yet..

[@adriangodley]

Hi Bob. I can confirm that at least one more was sold because I have it.

[@ea77hj]

26:16 - That strange tin piece under the center of the switch is short with the edge of the plate (Ground). That is all. 73, EA7HJ

[@NamasenITN]

I missed a final conclusion: is a design issue? Were the values of the inductors wrong? I noticed you did have a schematics in front of you: was it from MFJ? Thank you for your excellent video.

[@TheMaddogronh]

Another fine video,, but one question,,,,,, What did you do about the first problem with the DC input on the tuner that was not working right when you moved it ? Ron AC7RH

[@TRXLab]

nothing as it is not needed..

[@LarryKapp1]

I bought an MFJ DC distribution strip once and the main terminal binding posts were installed backwards - the RED was on negative and the Black was on positive. The soldering inside was horrible. I sent it back instead of trying to fix it.

[@TRXLab]

oh that is scary

[@w.rustylane5650]

It's hard to fathom that MFJ would manufacture a Bias Tee with the wrong parts. But then, even persons working in the manufacturing field could have a bad day and choose the wrong part for insertion into the product. It seems to me that even in the manufacturing of Yaesu radios, a person could not use enough heat sync paste on parts which eventually burns out the finals. W Rusty Lane K9POW in eastern Tennessee

[@stevejoos8953]

It looks like the two chokes in the Bias-Tee only have one turn of wire. Why not just cut the shrink tube off of the 2 chokes, re-wind it with about 8-10 turns of magnet wire, and then put new big shrink tube back over, and re-install ? I just got a Bias-Tee today, and checked it. Both chokes I have in my Bias Tee are the exact same physical size as yours, but you can clearly see 8-10 turns of wire under the shrink tube. Each is about 51 uH, and about 105 uH together.

[@roseelectronics4582]

Great! Great! Great!

[@vidasvv]

WOW, great catch ! TNX 4 the upload, 73 N8AUM

[@peterfardell9267]

I presume you checked out that suspected bad solder joint on the PCB. Did it need a solder "reflow"?

[@georgebecht6357]

Peter, What happened to the odd wire from the middle terminal of the switch to the PCB ground?

[@TRXLab]

i have taken it out

[@RGB06084]

I guess this is why MFJ is affectionally known as Mighty Fine Junk!

[@stargazer7644]

The circuit didn't match the schematic. That switch was wired to ground the bias lead via the inductors when it was switched off, and to apply +12v when it was switched on. The pad that had that weird sliver of wire/solder was already connected to the ground plane on both sides of the board. That's why it was showing a dc short between the dc pass pin and ground when it was turned off - it was designed that way. You can follow the PCB traces at 36:58 and 26:12 . The invalid inductor values were the entire problem. Typical MFJ quality control. Did you go back and fix that intermittent power input connection on the tuner?

[@TRXLab]

yes you are right but still that could be an operator error as well..

[@frantech6935]

My friend owned the ham store in Houston. They received product from MFJ that didn't work out of the box a lot. I recall he sold a G5RV wire antenna and it was returned because it didn't function. He gave it to a mutual friend. My friend opened it up and found the wires were never soldered from the factory. I got a 998 tuner brand new from him which didn't work out of the box. The quality from MFJ is not good. Mighty Fine Junk

[@TRXLab]

yeah it is sometime a pain in the back if you are the quality control of the factory...

[@montygore]

Hi Peter. Did you decide if the wire on the switch was installed from the factory? Thank for the videos.

[@TRXLab]

Well I think that was a production fault..

[@sinusgolf]

mfj products are well ingineerd,but the production is mainly by hand,so sometimes there are some issueus of course

[@adriangodley]

Hi Peter Excellent video as always. I have the same bias tee with exactly the same issue. Could you share the part number of the chokes you used in you repair. Thanks Adrian

[@TRXLab]

muRata 18473C; inductivity: 47 uH max (DC): 1.65 A max resitor: 55 mOhms

[@adriangodley]

@@TRXLab Thanks Peter

[@blackknight1397]

@@TRXLab i didn't see you do it but did you put the center connections of those inductors back into the board and solder? or leave them soldered together off the board?

[@hectorpascal]

What was the value marked on the chokes? From the beginning, the extra grounded switch connection looked obviously like a solder spash to me.

[@stargazer7644]

The pin the solder splash was on was already grounded to the ground plane. The splash didn't matter.

[@hectorpascal]

@@stargazer7644 Surely it was the splash that grounded the pin on the edge of the ground plane? Otherwise I don't see how it EVER could have worked!

[@TRXLab]

That is a good point.

[@stargazer7644]

@@hectorpascal If you look at the pin that had the splash on it, 36:58 26:12 it has no traces running to it and is grounded to the ground plane on both sides of the board. The pin to the left of it is also grounded to the ground plane on both sides. It is designed to connect the bias wire through the inductors to DC ground when in the off position, and to +12V when in the on position.

[@hectorpascal]

@@stargazer7644 So the schematic at 22:15 was wrong!? Maybe! - since either C4 or C5 also seemed to be misplaced. But could this circuit change contribute to L1/L2 failure at switch off, due to discharge to ground of any high value DC feed line capacitors inside the tuner? Unlikely if the inductor coil wire is thick enough - since inductors impede transient current change, and I doubt the voltage rise would be significant.

[@daveturner5305]

Is it possible that the case of the switch was meant to be earthed? If so would it make any difference to performance?

[@TRXLab]

no not really

[@sveinfarstad3897]

Super :)

[@johan-fredrikgrgaard2869]

The short in the switch burnt the inductors enameled wire so that the coil is shorted for HF, why not cut open the inductor and se what happend?

[@TRXLab]

hm most likely not because I got feed back that the unit initially worked...

[@stargazer7644]

That "short" in the switch was to a pin that was intentionally grounded on the pcboard - so it made no difference.

[@berndb.5097]

Unfortunately, some MFJ devices don't work out of the box. I have already noticed this several times :-( 73 Bernd

[@stargazer7644]

I always do a shake test on all MFJ items new out of the box before powering them up. There's usually one or more items loose rattling around inside. Their QA is a joke. Opening them up and looking for obvious problems is always a good idea.

[@berndb.5097]

​@@stargazer7644 Shaking is also an excellent idea :-))

[@transmaster]

The stories I could tell about MFJ.

[@TRXLab]

i believe that

[@cathrynm]

What a weird symptom. I have one of these, and jave not seen this problem, at least not so far. (Finger's crossed.)

[@TRXLab]

Yeah sometime it is weird so finger crossed

[@cathrynm]

@@TRXLab Nice to see you got it working. I was warned about these, but I'm pretty happy with mine. I mounted it up on a mast near the feedpoint of my dipole, and I've been using it to tune up on strange bands I can't otherwise use, like 90Meters. I have an amp, but I don't run power through it, mostly. I'm not sure how far I want to push it, really, since it's a pain to get to it if I burn it up.

[@k2icc]

After reading some comments, I believe MFJ is not that bad at all. Few of the ones that makes Ham radio to still exist, with affordable equipment. The problem is the lack of a good quality control. There seems to be technicians with great experience, but also long time workers in the assembly line that are not technicians, but know the equipment they work on inside and out.

[@TRXLab]

Thanks for comment

[@OldSal-d8h]

I’ve heard quality control issues. Hope the one I buy won’t have these problems. 73 de N9NY

[@OldSal-d8h]

Thank you Peter. Appreciate your providing us with a wonderful video! 73 de N9NY Gregg

[@DonDegidio]

Hi Peter, I have the same problem with my 998RT. Is the number on the choke 18473C? Just want to see if it's the same as yours. Stay safe. 73 WJ3U

[@TRXLab]

Unfortunately the number is not readable but it is a muRata and taking your number it makes sense inductivity: 47 uH max (DC): 1.65 A max resitor: 55 mOhms you can use it...

[@DonDegidio]

@@TRXLab Hi Peter, I have used my DE-5000 to test the two 18473C in series and it reads 3.2 uH. I lifted one leg on each choke to test. I removed both and tested each. One is 2.6uH and the other reads .023 ohms but no inductance. Using formula 14Mhz * 6.28*3.2uH I get 282 ohms impedance. I think that is the reason it does not work. WJ3U

[@TRXLab]

Absolutely right Don you caught the bugger :-)

[@DonDegidio]

@@TRXLab Hi Peter, I also checked the muRata website and it does list the 18473C as 47uH. Must be a mislabeled batch. I found some axial 100uH chokes that should work and ordered them.

[@TheEmbeddedHobbyist]

That DC blocking circuit in the tuner looks like it was fitted, as the unit did not have that option fitted as new. I would be very suprised if that was a factory mod. workmanship was just to bad. I never trust any unit that shows signs of people being in there before. nice fix

[@user-xj8oh6fo2f]

Actually it was installed by MFJ. You could google a lot of pics of MFJ 994BRT internals. All look the same.

[@TheEmbeddedHobbyist]

@@user-xj8oh6fo2f bugger me thats bad. How can you sell something with a mess like that. No wonder they seem to have bad press

[@TRXLab]

yes the should do it a bit better...

[@pherdantler707]

Would have lied to have seen an 'autopsy' of the iniductors. They might have been ruined by excessive RF power applied to the unit which may also have melted the solder connection on the switch.

[@TRXLab]

true but the video is already much to long...

[@Digital-Dan]

Friday PM or Monday AM product.

[@TRXLab]

lol yeah most likely

[@OleF112]

I am sorry for saying this but MFJ got worse and worse over the years. I saw very often corrosion inside because of bad seals, sometimes after only 2-3 years. I think that this failure is so unique, i would sent a notice to MFJ. That has nothing ti do with warranty, that is a thing of them believing in their own products. They could proof it by sending a brandnew BIAS unit. Peter, another good investigation comes to and good end, well done, great vid! 73 de Olaf

[@TRXLab]

Thanks for feed back Olaf. Yes quality control should be improved...

[@1967deek]

It's MFJ bad solder joints or solder shorts are the morm it was clear as soon as we seen inside

[@TRXLab]

Thanks for watching

[@doccybug]

Good morning, great videos as always. I have sent you an email regarding a Icom7800 that belongs to a family member in Denmark. Kind regards vk3ajk - Melbourne , Australia

[@TRXLab]

thanks! e-mails yeah have a backlog of appr. 150

[@tortsen2]

Diese kleine Metallklammer wird beim MFJ-4116 als Brücke anstelle des Schalters benutzt, ich habe heute nämlich einen SG-230 mit so einer Platine versehen, ist absolut identisch nur ohne Schalter. Was die Verarbeitung vor allem die Löt Qualität angeht, absolut unterirdisch. Ich habe alles nachlöten müssen. Ich vermute hier wurde eine Platine benutzt die für einen 4116 vorgesehen war und beim Schalter einbauen ist die zuvor entfernte Drahtbrücke irgendwie mit eingearbeitet worden. Hauptsache der kleine rote Quali-Aufkleber war mit Handzeichen versehen aufgeklebt. Was die Spulen angeht, sind bei mir die gleichen verbaut, ich habe keine SWR Probleme. Ich habe sie allerdings auch nicht gemessen. This small metal clip is used as a bridge instead of the switch on the MFJ-4116, because today I have equipped an SG-230 with such a circuit board, it is absolutely identical only without a switch. As far as the workmanship is concerned, especially the soldering quality, absolutely underground. I had to re-solder everything. I suspect a circuit board was used here that was intended for a 4116 and when installing the switch, the wire bridge that was removed earlier was somehow incorporated. The main thing was that the small red quality sticker was affixed with hand signals. As far as the coils are concerned, I have the same built in, I have no SWR problems. I didn't measure them either.

[@TRXLab]

What clip do you mean?

[@tortsen2]

@@TRXLab Ich meine diesen kleinen gebogenen Draht, der den Kurzschluss verursacht hat. Schade dass ich hier kein Bild reinstellen kann, habe Fotos davon.

[@wolfhawg]

MFJ strikes again.

[@TRXLab]

every now and then

[@stevec5000]

I guess he's never seen the sloppy assembly work from MFJ? It's best to remove the shorts and solder bridges and go on without wasting a lot of time.

[@happymark1805]

it's MJF,also known as More Fucking Junk, so you can expect poort quality components, bad soldering and very poor quality control

[@bblod4896]

True.

[@rowifi]

Best watched at x1,5 speed

[@TRXLab]

correct

[@richiet3841]

Mighty fine junk. Martin's reputation is unchanged for decades. His firm has NO QA dept and it seems he hires kids off the street to perform soldering. Almost every piece of test equipment or gadget from MFJ is suspect. Have a screwdriver ready at all times. Also his designs for interfaces were great.... In 1972... Who uses DiN connectors for keyboards? The SWR analyzers use 10 AS batteries and you can blow a diode just by turning it on if the UHF button is pushed in. A known issue for decades.

[@tubeDude48]

Pull the switch *ALREADY* geez!!!

[@bushpig59]

I agree I hung myself three times😳

[@Mr_Meowingtons]

The interface for this tuner is absolutely ridiculous literally what's wrong with just having a control cable that goes from your Shaq to the tuner?

[@stargazer7644]

Because it is far more convenient to run power up the coax. Some rigs can even do this automatically.

[@petermartin6031]

MFJ - money for junk!

[@TRXLab]

Thanks for watching

[@bukucsjozsef9630]

This is MFJ factory dis/quality. My MFJ-259b has ugly solders, flux and resin everywhere. Itself MFJ products are great but the build quality poor.

[@TRXLab]

Thanks for feed back

[@herbertsusmann986]

MFJ is known for poor quality parts and poor quality workmanship. They are a low budget manufacturer for sure. If that tuner is rated for 600 watts RF I would worry that those inductors you put in can handle that level of power. I would take off the heat shrink from the original chokes and look for any damage to the windings from overheating. Was there any inductance value marked on those original chokes?

[@TRXLab]

Thanks for watching

[@ptronix]

I remember having an Mfj atu here 30 years ago, none of the connections to the coil were soldered! Quality control a joke. Hence "made from junk"

[@TRXLab]

Thanks for feed back

[@bushpig59]

I’m sorry I’m Normally the most patient fellow in the world but this video I’m sorry it took waaaaaaaayyyyyyy to long for your explanation of a very substandard device. Yes I was thrilled to see a possible dry joint and a short to earth I had seen this in the first nano second and yes your a proud American (maybe from my Oma’s place originally) And yes you have impressive Radio Shack with every possible test device. But do you have 4X1000 or an 807? Anyway it was interesting for the first ten minutes. I know your proud but I have ADD and I almost necked myself. I don’t want you to change your ways but I am trying to be honest.

[@TRXLab]

Thanks for feed back. The good thing is you have the freedom to stop watching and skip my video for something else.

[@blackknight1397]

oh yeah, and dont be a dick

[@user-dr4wj7qm7w]

By

[@notkomermerski7277]

Yeah, it looks like it's assembled by a bunch of blind kids in a dark cellar

[@TRXLab]

Thanks for comment

[@petenikolic5244]

Bridged contacts "but not to ground " to prevent a floating contact. Typical MFJ construction you know what MFJ stands for i wont put it on here

[@Ace411275]

Mighty Fine Junk

[@petenikolic5244]

@@Ace411275 your getting there

[@karlfell3768]

MFJ = Junk. None existent quality control. The chokes were cooked by the big ugly short to ground. Given the size of the cores I would have been tempted to rewind the chokes by hand. Karl

[@TRXLab]

Thanks for watching

[@stevec5000]

MFJ is very poor quality, just look at the work they did connecting power wires to the antenna tuner board!