#96 Repairing a 1500 Watt MOS FET HAM radio RF Power Amplifier

In this episode we fix a HF PA with burned PCB and have to find the cause why it burned. Therefore we perform a lot of testing.
Native speaker choose 1,5 or 2,0 video speed.

[@zoranconjar6815]

An excellent example of how, with high knowledge and the possession of quality measuring and diagnostic equipment, you can achieve excellent results. Thanks for your time and demonstration.

[@MrCarlsonsLab]

Yikes, I bet those FET's a worth a bundle! Nice that it was just that board. Thumbs up bud!

[@TRXLab]

750 each...,Paul. Happy that these survived... Thanks for stopping by. Hey bud what's going on where are the new vids?? Take care 73

[@hankbizzo5]

Wow 2 of my favorite KZbinrs.. Thank you for all the great content, keep up the awesome work!!

[@mitch3064]

@@hankbizzo5 My thoughts exactly. Call me what you will but to me it is sort of like reading Issac Newton and Albert Einstein writing to each other(yes I know they could not do that). These two along with Dave from EEVBLOG, and ElectroBoom are my favorites, electronic Gurus.

[@andrewmullen5770]

Me too! They both provide so much information and inspiration. In my perfect life i would be doing these things for a living!

[@JustinRuth-km4wz]

Hello Mr Carlson you are amazing man. Listen we deal and work with the 188 ldmos chip ..I'm a big DX guy and build my own amps and modulators... Love your channel and what u do ..ur channle along with this one are by far my fav

[@lyntonprescott3412]

Fantastic repair way beyond my level of competence and understanding, but you explain things so well I can get my head around most of it. I bet you could make my old FRG 7 really sing! 73’s Lynton

[@dennisbauer3315]

That was better than watching a movie, It was good to watch and learn, thank you TRX Bench.

[@glitch1182]

This is amazing. Watching this video and how you methodically progress through troubleshooting the amplifier made me appreciate the work that was involved in its design and construction. I wish I knew enough to be able to build one of these. I don't know where to get a primer on filter networks, and I don't even have faith in my ability to build a power supply of my own design. Someone else's, absolutely!

[@TRXLab]

Thanks for feed back Ahmed. 73

[@patrickpafarnis5798]

Again a very nice instructive video, however I'm a technician but not well-versed in high frequency technic, but your outstanding explanation did me understood everything very well. As I mentioned before with your explanation with the switching power supply, your english is for me as a dutchy, 100% understandable and more clear then a native speaker. Thank you very much!

[@TRXLab]

Hi Patrick, thanks for the feed-back glad that you like it. 73

[@MicheIIePucca]

You have some nice test equipment. The analyzer to view frequency and the SWR as you switch between the bands gives a cool perspective of health all at once. As always I find watching these videos so interesting, and entertaining, while at the same time trying to learn something more each time I watch one.

[@TRXLab]

Glad that you liked it Michelle! Thanks for stepping in 73

[@buckaroobonsi555]

That harmonic suppression is beautiful at that output power level!

[@TRXLab]

Right it is really not to bad. All the filtering is just working fine 73

[@user-uv4xe3cq2y]

I must have missed the AFP re-adjustment that started the whole problem? Thanks Peter for another great video. I appreciate your attention to detail.

[@g0fvt]

Great diagnosis, it is too easy to rush through a repair, well done for checking the low pass filters. 73

[@TRXLab]

Thanks for Feed-back 73

[@PhilipEvans11]

g0fvt hi I have an fm 250w- 300+ and it was given to me with a working amp with driver for spares the transistor blf25 are the same but -I wonder if you could advise me why side is rd in and out as there is 2 bnc on the case of The spare I no power around 30-46vdc input2-4w maybe less I want to add a LPF to it with power and drive

[@g0fvt]

The collectors of the transistors will usually drive the output transformer, the windings of that will generally follow a short path to the output BNC. Even if you get input and output connections reversed you are unlikely to damage the power stage as long as the drive is not excessive

[@YvoMunizAlphaTelecom]

Another great video Peter! Very well explained. I liked your dummy load... I have a EKD-100 for restoring.73's

[@TRXLab]

Hey Yvo, nice to see you and thanks for your feed back! Yeah the RFT devices produced in the former GDR are really rough and good for heavy duty. Hope you will do a video on the EKD-100 nice SW receiver. Take care my friend 73

[@gregorywest2029]

Great video Peter, like the safety test performed. Keep them comming. Thanks, Greg

[@TRXLab]

Hi Greg, thanks for stopping by, Yeah I always perform this safety test after fixing a device with internal 230V power supply. 73

[@jimsutherland501]

The world needs more people like you! Genius

[@TRXLab]

Thanks Jim!

[@montygore1200]

Hi Peter. All of your videos are very informative. This one to me really shows your extreme knowledge. I would love to own this amp. I wonder how many the old guy built. Perfect for a transistor amp. I would really love to own this one. The owner should be thankful for you knowledge and to own such a nicely designed amp. Very nice to see it repaired.

[@N1RKW]

Well done! Good repair and good video, as usual! Thanks, Peter! I found myself wondering through most of the video what could have done that kind of damage, but then you found the SWR protection circuit was out of adjustment and the small, seldom used part of my brain that stores useful information realized that a high SWR situation could mean that there were some seriously high RF voltages playing around inside that amp.

[@TRXLab]

LOL yeah some seriously high RF :-) Thanks for stopping by Adam! Take care 73

[@subramanianr7206]

@@oldjarhead386 yes, very appropriate question and he had not shown the same on the video 🙄 De VU2RZA

[@billharris6886]

Hello Peter for making the nice video, with a thorough checkout of the amplier circuits. I designed some high reliability airborne power amplifers in the past and wanted to add a few recommendations. Since this amplier is for amateur use, the standards I recommend will be somewhat less but, still useful for general guidelines.

[@hamradio599]

I like your DCA55 component tester. It's really useful.

[@hancecrawford]

well done Peter that is good testing to check for earth leakage very important were safety is concerned I used to do P.A.T testing Pats stands for Portable Appliance and Testing.

[@chickennugget3362]

Another great video! I'm going to have to watch it another 6 times for it all to sink in!

[@asz620]

Hello Peter!!!...Very nice work, I really enjoy watching your videos!!!

[@tl2797]

3:49 oh WOW! Thank you for great videos!

[@wadehicks9270]

You do great work Sir enjoy viewing your videos and learn a few things too. Thanks for sharing.

[@TRXLab]

Hi Wade, Thanks for watching. I'm glad that the videos are interesting to you. 73

[@martinda7446]

Absolutely wonderful, entertaining and delightful. Glad to be a subscriber.

[@TRXLab]

Thanks for the kind feed-back Mart! 73

[@TheRadioShop]

Very detailed analysis of the issues Peter. That was a lot of testing to go through. You really did a good job of explaining that. You thing it may have just been a weak link in the board that caused the failure? Or maybe that tiny capacitor shorted?Thanks for the great video my friend.

[@TRXLab]

Hi Buddy thank you. Well really not 100% sure what the cause was as other than the pot for swr all turned out to be good.. May be it was a bad solder point on the burned board but that is not certain. Thanks for watching my friend. 73

[@K1ZEK]

Enjoy your videos and this one was no exception. I read through the Q&As of others and now have no questions. Good job 73 Leo K1ZEK

[@TRXLab]

Thank you Leo! 73

[@JamesP6084]

Very thorough testing very impressive Peter, as usual 73's VK6NJP

[@TRXLab]

Yeah a lot of work to make sure that the PA is working...Thanks for watching Jim 73

[@dinosworkshop6870]

Very concise and very detailed. A terrific video !!!!!!!!!!!!

[@TRXLab]

Hi, glad to see you!! Hope you are okay. Thanks for watching and comment 73

[@iw0hex]

Another great lesson, thanks Peter. 73s de IW0HEX Pasquale

[@TRXLab]

Glad that you like it Pasquale. Thanks for stopping by 73

[@RC-Heli835]

This is spectacular!👍😃

[@dondonaldson1684]

Did you readjust the AFP trip point and make sure that the adjustnent pot wasn't intermittent?

[@herbertsusmann986]

Very nice video Peter. That is quite an interesting amp there. Almost looks homebrew, I guess it was homebrew in more than quantity 1?? Good that you could order a new board. I was thinking you would have to make your own! This kind of amp makes me a little nervous with so much power you can really do damage easily to very expensive parts. Vacuum tube amps are much more tolerant of abuse compared to MOSFETS!

[@TRXLab]

Hi Herbert, yes as I said at the beginning it is a semi professional PA and was build a couple of times. It is based on a Motorola application note for the mos fet's..That is the reason why you still get spare parts for it from the USA. Thanks for stopping by 73

[@GaryLordsWayMinistry]

I think the guy who ran the amp lost his antenna and threw the match out of the final stage of the transmitter's load network to the antenna and it fried the final stage of the transformer PI circuit when it got out of tune when the antenna went up in smoke. So we found that the swr protection section didn't work properly to cut power off to the output section of the power to the finals due to a bad pot trimmer. But what caused the high SWR to begin with the operator most likely. Not selecting the right band for operating of the band of output of the radio.

[@worroSfOretsevraH]

Nice video! I really would like to take a look inside that 1200W RFT dummy load. Thanks, 73.

[@TRXLab]

Hi, well there is really nothing exited to find only the full capsuled dummy and rough fans.. Thanks for watching 73

[@stevenandros4586]

Very enjoyable video (still watching it). The SWR detection circuitry is likely between the LPF and the antenna connector. In that location it is unable to protect the FET's in the event of a LPF failure. I have a pair of those FETs for sale should you want a spare. Cheers and 73 - Steve KG4LJB.

[@TRXLab]

Hi Steve, thanks for feed-back! All the best and 73

[@Chipz0r]

One hell of a way to keep the shack warm. 73

[@TRXLab]

LOL yes that is right.. 73's

[@Gw0wvl]

This is why i prefer Valves to High power transistors, For instance The cost of a GS-35 valve is a fraction of the cost of a high power transistor and a lot more forgiving...... Great video , But Ide take a high power valve over a transistor anyday :-)

[@TRXLab]

Yes you are right valves are a lot more forgiving... Thanks for watching and comment 73

[@Gw0wvl]

Its my pleasure, I always watch your videos, Your knowledge is superb... Thankyou..De Gw0wvl ... 73

[@andrewrae2813]

Excellent video as usual. This channel recommended by Mr. Carlson's Lab.

[@TRXLab]

Hi Andrew thanks for watching and feed-back. Paul is a very nice person!! All the best Cheers

[@sputzelein]

Very good explanations. Networkanalyzer: would be interesting to know what komponents you need for it.

[@TRXLab]

Hi, thank you! You find all about the network-analyser in video #77. 73's

[@1112223333111]

those mosfets are super tough, good to 50:1 swr at full load.

[@TRXLab]

Yeah this MOS-Fets are monsters :-) 73

[@glaros0]

Dear Peter, I've really enjoyed this video, very instructional and well explained. I think I will see it again, I enjoyed it a lot. So, perhaps the cause of the problem was the setting of the variable resistor (51:49) that senses the reverse voltage level? Best, 73, Kostas

[@TRXLab]

Hi Kostas, glad that you like it and thanks for comment! Well the reverse swr voltage was the only finding after all that testing. But still it could has been a cold solder joint on the burned PCB as well but that we will never know.. All the best 73

[@subramanianr7206]

@@TRXLab but I am not convinced De VU2RZA

[@Mrjm5411]

Enjoy you videos Peter. Would you consider a video on the Rhode & Schwarz CMT setup and use? Thank you!

[@TRXLab]

Hi, thanks for stopping by. Well yes hat video topic is already on the list only time is the issue.. Cheers.

[@19ac471]

hallo peter, ich habe jetzt einen eintrap in meinem besitz. Haben Sie vielleicht weitere Informationen zu dieser Endstufe? Ich würde gerne wissen, wie hoch die maximale Leistungsaufnahme ist. und ist es gegen zu viel eingang und hohes swr geschützt. bvd Stefan PD5S

[@mylesl2890]

i missed what caused the failure?

[@jonka1]

I didn't see if you adjusted the SWR protection circuit with high power. Did you leave it at the sensitive setting from earlier?

[@magicwoody]

schönes Output Signal.. sehr nice 73

[@douro20]

Can this transmitter handle being keyed down around the clock?

[@PapasDino]

Nice fix Peter. Even though the PA voltage is ~50VDC did the builder include a safety interlock? I'm used to working on my venerable Drake L-4B tube amp and cringe at seeing a open amp like that just from my experience! ;-) What did you end up setting the SWR threshold at for kicking the amp out of line? It's interesting to note that there was no apparent damage to the pot(s) in the sensing circuit and ever more interesting that one could have changed value sufficiently to allow the amp to operate into a high SWR condition and thus the over-current situation. I'll bet the moment it blew was exciting! 73 - Dino KL0S

[@TRXLab]

Hi Dino, no the builder did not include a safety interlock but with 50VDC I'm not really scarred. You still have to take care fore sure as you don't want to touch RF with 1,5KW but it is different to tube PA's with up to 5KV circuits...I set the swr threshold to 2,5:1 and cross fingers that there is not an additional hidden fault which didn't show after all testing. Yeah it is always the problem with semi professional devices as you can't really check the values against production values. The pot for itself was working okay on ohm test without any drop over the range. I was not present when the amp blew but what I have heard it was somewhat frightening...Thanks for stopping by 73

[@mariamkarnaugh8861]

I did not get the cause for the damage - although I watched the whole video. Did someone use the wrong filter settings resulting in a high vswr which was not detected?

[@quadrant2005]

I think a Mica Capacitor failed

[@wab1954]

Great video!! Maybe I missed it but did you check the SWR protection circuit after you repaired the amp?

[@TRXLab]

Hi, no you don't missed it, I have done it off camera it is set to approx 2,5:1. Let see how it works. Thanks for watching 73

[@LynkedVideos]

I wish my German were as good as your English. I just noticed your suggestion for native speakers to choose 1.5x or 2.0x speed. Well, I don't find that necessary. Ich finde deine Videos fantastisch. Your repair was methodical and thorough. I especially liked the addition of a mains test at the end. The threshold voltage on each MOSFET was 1.39v and 1.41v. What difference is acceptable? Beste Gruesse, Michael / KJ7WC

[@TRXLab]

Thanks Michael for the kind feed-back. It is not the bias voltage what's matters but the current! The different voltage is only because the transistors are not matched.. All the best 73

[@izzzzzz6]

Rule No.1 don't play with the pots and cans unless you know what you are doing. Sometimes the pots become corroded and no longer give the correct resistance, just turning it a few times can clean it up but sometimes they need changing out.

[@ernest4all]

Danke fuer deine video! Sehr gut! Danke schön.

[@TRXLab]

Thanks for watching Vielen Dank und schöne Grüße 73

[@waynejourdain]

very informative

[@wadehicks9270]

Meant to ask you how much current will those finals handle on their outputs thanks.

[@TRXLab]

There is a powers protection at 50A for total current. Hope that gives an idea.. 73

[@Slartibartfas042]

Probably Scenario might have been: SMD multi-layer ceramic condensor dying for micro cracks by heat or maybe even from excessive voltage (maybe by VSWR misalignment?) and then being burned off in a few seconds at that rates could lead to excessive oscillation of your Amplifier. That would then lead to massive over voltages which then are sparking over and burning the massive hole into your PCB. Don't you think?

[@tomsmolcnop6358]

Irish Vikin

[@mje3055]

very nice

[@DonDegidio]

Peter, Another nice video. Two thumbs up. :-) WB3BJU

[@TRXLab]

Thank you Donald! 73's

[@gastarbieter]

what is your full time employment? Can you please do a little video on your education and work experience?

[@MrKeithsplace]

Kaboom, at first glance, not being a tech but electrician, I would have guessed that as a lightning strike.

[@TRXLab]

one could think so

[@drstrangelove09]

problem determined and fixed at 52:17

[@TheBucc69]

very nice 🙂

[@GraviranjeBeograd]

Sir Have u ever repaired Co2 laser RF Amplifier. thx

[@stefanogangale4780]

good mrf157 mached par??

[@jeffminnick5209]

Another great job Peter. ... sweet amp!!!

[@TRXLab]

Thank you Jeff 73

[@douro20]

This is why I say no one should be using solid-state transmitters in broadcast! Another reason is what happens when a transmission tower gets struck by lighting... I wonder how well SiC MOSFETs would work...

[@subramanianr7206]

You are absolutely wrong in your assumption. De VU2RZA

[@wgdavis5353]

What is a tarrisster?? ♠W.G.

[@jihad355]

good job and nice video

[@TRXLab]

Thank you

[@DAVIDGREGORYKERR]

Should the board that the output transformer have been made of ceramic material so the problem doesn't happen again.

[@subramanianr7206]

Ha..ha..ha.. De VU2RZA

[@stevenfeinsmith3567]

No closed captions????????????????????????????????????????

[@buckaroobonsi555]

I guessed the problem after I saw the initial damage. Nothing else looks like damage from massive stray rf energy not on living tissue and both on electronic parts. The voltages and currents on the ac and dc inside the unit are not that high not compared to a tube amp. I have seen rf burn and blast wholes in things before. The fact that the output transformer took the brunt of the damage and most of the caps where left in tact is telling.

[@TRXLab]

Yes you are right it was in indication for that. Thanks for watching 73

[@notfallmed]

Great,tnx. DO5NET Peter 73

[@TRXLab]

Vielen Dank fürs reinschauen 73

[@notfallmed]

Immer wieder gerne, klasse gemacht, Top, Grüsse Peter

[@JustinRuth-km4wz]

These i believe arw srf 157

[@doctorbills790]

Nice job but I don't think you ever found the cause of the failure...

[@TRXLab]

Well it simply happens very often that it is not possible to find the root case. Sometimes it is simply a part ageing issue. But anyway you have to try it and do the best you can to avoid to blow an expensive spare part. This amplifier is still working after repair... Thanks for watching ..73

[@lesjohnson9740]

Thank's TRX yet again , Les G4XMX.

[@TRXLab]

Thank you Les! 73

[@TKomoski]

The Best 1

[@TRXLab]

Thanks Tom. Cheers

[@TKomoski]

very good

[@billharris6886]

This particular amplifier probably failed for 3 possible reasons: (1) The operator was running too high an output power. (2) High power was used during high VSWR. and (3) The copper clearance on that output transformer board is insufficient. The board thickness and copper clearance should be about 3 mm to reliably handle the expected RF voltage levels. The transistor checker will only check the basic functionality of RF power transistors. A common problem is partially blown die bond wires, which will vastly affect the transistor impedance and output power capability but, will check good with this type of tester. The path from the power amplifier to the RF output connector on the unit front must have an insertion loss of 0.3 dB or less and a return loss of greater than 20 dB within the pass and of the filter. Failing to meet these specs makes the amplifier less stable and generates extra (unwanted) circuit heat.

[@subramanianr7206]

Valid points... thanks for the observation De VU2RZA

[@billharris6886]

@@subramanianr7206 You are quite welcome, just passing on things I learned when redesigning RF power amplifiers for increased reliability for Collins Radio some years ago. De AC8AQ.

[@subramanianr7206]

@@billharris6886 hi, that's really wonderful. Yes, we must be in a position to make a conclusion to what would have caused such a catastrophic failure if not fatal in the sense torching the entire shack. I do have a board with MRF157 which are known for ruggedness. SWR protection circuit not hitting in can be sceptically thought of any average ham, I believe. Thanks again for your response 👍 De VU2RZA

[@billharris6886]

@@subramanianr7206 After looking at the video a second time, it looks like the failure was caused by an RF bypass capacitor on the bottom side of the output transformer board, that developed a high resistance short (a few ohms). There should have been about 10 RF rated, low ESR capacitors bypassing that trace for the amount of power this amplifier is rated at. This is a problem I see regularly; the maximum ratings of the components are ignored and "gut feel" is used instead during the design phase. The other design problem seen regularly is: mis-application of a component, such as using solid tantalum capacitors on a power supply line. Just one (or a few) prototype unit was likely built up before the design was launched into Manufacturing. The prototype unit was likely never exposed to "Real World" testing (such as the antenna arcing during voice peaks) and the components held up because they performed better than Spec for the duration of Engineering's hurried tests, done to meet an unrealistic design schedule. Most high RF power amplifier designs have inadequate protection circuitry and/or the circuitry reacts too slowly. With the power levels used in this particular amplifier, the protection circuitry needs to effect the overload condition in 100 usec or less. This is because RF power transistors (especially bipolars) perform best when operated close to their breaking point. The protection circuitry needs to detect average and peak overloads, then throttle back without ringing. These are not simple designs, and are on par with the design of a nuclear power station if the amplifier is used in a mission critical application.

[@billharris6886]

@@subramanianr7206 The MRF157 looks like a really nice device from the Datasheet. I never designed any power amplifiers with FETs, they were just starting to come out when I worked for Collins. Due to their higher input impedance, they are much easier to work with as far as broadband matching goes. In a push-pull configuration, I wouldn't try to get any more than 900 watts from the pair. Transistors that large would absolutely demand a copper heat spreader between the transistor case and the aluminum heatsink; the aluminum just can't conduct the heat away fast enough.

[@IFIXCASTLES]

Blown out by someone that keyed up too long...like one of those chuckers...

[@mattmoreira210]

_Somesing_ is _vrong_ _wiv_ _zis_ comment. :/

[@samuelsmith6573]

Matheus Moreira comment is spelt VI's der K as in komment! Ya!

[@mattmoreira210]

LOL! I was being sarcastic.

[@OldSweetTed]

I always appreciated my repair folks, but even more so after following along this diagnosis & repair!

[@TRXLab]

Thank you Jim! All the best and 73

[@maracas8692]

Which mosfets use this amp, and what 's the voltage supply for this amp? thanks

[@Pieh0]

They look like MRF157's, even though they are 600w fets, but it's bound to be something in that range.

[@subramanianr7206]

50-55V. But it can work on little low and high voltages. De VU2RZA

[@justinruth9729]

This guy is next level technician...period prolly the best on entertainment

[@billharris6886]

A good power amplifier will have protection circuitry that monitors forward power, reflected power, input power, output power, output device DC current, output device power dissipation, and of course output device junction temperature. In most cases, the protection circuitry should reduce input drive to properly protect the output devices. The protection circuit should never abruptly cutoff power because, this can generate damaging transients. Instead, it should fold back ouput power like a power supply folds back current when the current limit is exceeded. With the amplifier you are working with in the video, the manufacturer may have set the cutout point at a specific reflected voltage on the directional coupler (which relates to a reflected RF power level instead of an actual VSWR ratio). For best reliability, output power should start folding back at VSWR ratios greater than 1.5:1.

[@kingsqueak2221]

So thorough and takes a lot of time to put a careful video together as well. Very useful. I'm only just starting to understand so many concepts with amplifiers and information like this is very helpful. Thank you for doing these. All of this to talk to OMs, makes our hobby seem kind of silly really. :-)

[@TelstarElectronics]

OMG... all those protection circuits... and it burned a 2" diameter hole in the board! Not a very good design. And what caused that burning? Better find out, or it'll just burn again.

[@carlos735]

The experts in RF Amplifiers are very rare and you are one of them, you got a new subscriber

[@KH07734]

I spent 4 years learning electronics in grade school. I use basically the same process you use to troubleshoot. My eyes are less than normal lately so Ibtake a bit longer to complete the tasks.

[@WB2GPU]

Your analysis and process of elimination is great. The only problem here is that there is no explanation for the blown board. It takes hundreds of amps to burn a gaping hole in a board that is mostly copper on both sides. Since it is a high current arc from the Antenna jack to ground, it would appear there may have been a nearby lightning strike. The protection circuits could do nothing to stop this. I don't believe the energy came from the internal power supply, I have to believe it would have folded back or popped a fuse. It would need to see a direct short and only limit the current to max for many seconds or even minutes to burn like that. That was a done in milliseconds.

[@andrewandrosow4797]

1206 and bigger capacitors were often short-circuit in my hobby devices - i suppose, it was because I don`t have an infrared soldering station. 4:14.

[@tubeDude48]

EXCELLENT !!!

[@TRXLab]

Thank you

[@eduardosomoanocrematy7802]

Dear friend forgive the daring to write to him on his channel but I would like your opinion technique of the problem of my Yaesu FT-450. Here I explain what happens with my Yaesu FT-450. A few days ago I made the mistake of trying a radio from a friend of mine when my FT-450 was on receiving, they had two different antennas but the separation between the antennas on the roof are 3 meters. When I was testing the radio in transmission I felt a burning smell from my friend and I realized that it was coming from my radio, at the moment I turned it off and when I turned it back on it had changed many things like: - TRANSMIT BUT DOES NOT GIVE ANY OUT POWER IN (AM) MODE ON ANY BAND. - THE SYSTEM (ALC) DOESN'T WORK, NEVER MARK ANYTHING ON THE DISPLAY, BEFORE IT WORKED VERY GOOD. - ESPECIALLY IN 6M (50MHZ) BEFORE HAD 100 WATT, NOW ONLY HAS 10WATT AND WHEN CW OR SSB TRANSFER FEELS MY VOICE OR NOISE IN THE RADIO HORN. - THE INTERNAL RADIO TUNER ANTENNA DOES NOT ADJUST IN SOME BANDS AND HIGH SWR WITH GHOST ANTENNA DUMMY 50OHM ADJUST 1: 1 ALMOST ALL BANDS, I REMOVED THE RADIO TUNER ANTENNA AND CONTINUES WITH THE SAME PROBLEM, THE PROBLEM IS NOT THE INT-TUNER OF THE FT-450. - BEFORE ALMOST ALL BANDS DRAWN 100 WATT CW AND ALMOST 90 WATT SSB. NOW HIM RESULT WITH LOAD DUMMY 50OHM PER BAND IS: 160m ... fm .... 100 watt cw .... 100 watt am .... no carrier no power fonia and digital .. 100 watt ----------------------------- 80m ... fm .... 100 watt cw .... 100 watt am .... no carrier no power fonia and dgital .. 100 watt ----------------------- 40m .... fm .... 70 watt cw .... 70 watt am .... no carrier no power fonia and digital ..40 watt ----------------------- 30m ....... fm .... 70 watt cw .... 70 watt am .... no carrier no power ----------------------- 20m ....... fm .... 70 watt cw .... 70 watt am .... no carrier no power fonia and digital .. 40 watt ----------------------- 17m ....... fm .... 50 watt cw .... 50 watt am .... no carrier no power fonia and digital .. 30 watt ------------------------ 15 m ........ fm .... 80 watt cw .... 80 watt am .... no carrier no power fonia and digital .. 80 watt ------------------------- 12m ......... fm .... 80 watt cw .... 80 watt am .... no carrier no power fonia and digital .. 50 watt When I transmit on the phone you can hear it on the radio horn ------------------------- 10m ......... fm .... 50 watt cw .... 50 watt am .... 10watt fonia and digital .. 50 watt --------------------------- 6m ......... fm .... 20 watt cw .... 20 watt am .... 20 watt fonia and digital .. 20 watt, When I transmit in fonia it is heard in the radio horn. He also seems to be crazy, he makes noise and he seems to have serious problems. I RESET HOME OF THE RADIO AND CONTINUE WITH THE SAME PROBLEM, THE PARAMETERS THE HIDDEN MENU IS CORRECT, THE RECEPTION IS CONSIDERED GOOD IN ALL THE BANDS AND MODES. I CHECK THE BOARDS OR BOARDS AND ALL ARE IN GOOD PHYSICAL CONDITION, NONE COMPONENT SEEMS TO BE BURNED. BEFORE MAKING THE ERROR MY RADIO WAS WORKING NO PROBLEM WITH 100 WATT IN ALL THE BANDS AND THE AUT INT ALSO WORKED NO PROBLEM. I HOPE THAT WITH THESE DATA YOU CAN GIVE ME AN IDEA OR OPINION OF WHAT PROBLEM THE TEAM HAS THOUSAND THANKS IN ADVANCE. note :Now I have realized that when I press the ATT or IPO key that is only for reception it falls even more the power in all the bands, in addition I tested it in reception 6m 50mhz and it has problems also at the reception . BEST 73.- EDUARDO CO8LY

[@thefreese1]

I kind of skipped through the video . Did he change out that potentiometer on the overcurrent board ? I would have changed them both .... That was a great Video . I'm building a LDmos amp using a Gemini style chip . Actually a BLF188xr .... Only thing I didn't like about this amp I saw was the single choke on the output board , but other than that , This is a well made, clean , amp....

[@hornsby5533]

RFT KAM-1300 does a good job. 😁

[@trcostan]

I don’t like the way that transmission like transformer board is built. The spacing is very close!

[@izzzzzz6]

you could scroll around the 12M band to see where exactly that filter is tuned and then possibly re-tune it.

[@delangaming5384]

Why most of foreigners they took to much time of ther blog.. To much talking even short problem on board

[@toastnotoflondon8500]

Excellent and informative. Thank you.

[@SquantoTerror]

Great video once again! I really enjoyed your explanations and walking us through the procedures to test and repair this amplifier. Very well done! 73!

[@TRXLab]

Thank you very much Nicholas! 73

[@justinruth9729]

Wonderful amp quality

[@johngulliver6151]

Great video again I really enjoy your videos you are a very good engineer and your commentary is very clear to follow I sit and watch always with interest .Thanks again for posting

[@TRXLab]

Thank you John glad that you like it...73

[@repairfreak]

Another interesting video viewed, great job as usual Peter.

[@randyterrell2261]

Peter, great video. Been playing with high power solid states PA's for years but still learned a lot of the newer techniques. Good job!

[@TRXLab]

Thanks for watching Randy! 73