#96 Repairing a 1500 Watt MOS FET HAM radio RF Power Amplifier
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- čas přidán 3. 06. 2016
- 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. - Věda a technologie
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.
Yikes, I bet those FET's a worth a bundle! Nice that it was just that board. Thumbs up bud!
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
Wow 2 of my favorite CZcamsrs.. Thank you for all the great content, keep up the awesome work!!
@@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.
Me too! They both provide so much information and inspiration. In my perfect life i would be doing these things for a living!
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
The experts in RF Amplifiers are very rare and you are one of them, you got a new subscriber
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.
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
That was better than watching a movie, It was good to watch and learn, thank you TRX Bench.
I always appreciated my repair folks, but even more so after following along this diagnosis & repair!
Thank you Jim! All the best and 73
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!
Thank you very much Nicholas! 73
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!
Thanks for watching Randy! 73
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.
Glad that you liked it Michelle! Thanks for stepping in 73
Nice work, Peter. Thanks for sharing the repair with us.
Thanks for watching Rober. 73
Great video Peter, like the safety test performed. Keep them comming. Thanks, Greg
Hi Greg, thanks for stopping by, Yeah I always perform this safety test after fixing a device with internal 230V power supply. 73
An excellent,methodical and complete repair, Peter. Very enjoyable to watch. Thank you. 73.
Thanks for watching 73
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!
Thanks for feed back Ahmed. 73
The suggestion for the changing of the video speed was spot on. Thank you. It actually helps in other ways. Somewhat often people on CZcams talk a little fast for my old brain, so your speech pattern, at 1.25 help smooth things out, and not be too fast for my comprehension. Your English is fantastic. My ability to sprechen Sie Deutsch ist sehr klein. Maybe 30 words left over from learning a bit from my girlfriend while I lived in the city of Bitburg for a few years. Nice addition to learning some of the language was that her father was a distributor for Bitburger Pils. 40 years of not using it hasn't helped.
Thanks for the kind feed back Mitch and really glad that you liked the video! Hope you still enjoy Bittburger lol. Ich wünsche einen schönen Sonntag 73
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.
Thank you very much, as always, Peter!!! Great video as always!! That is one impressive amplifier!!
Thank you Brian! 73
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
Thank you John glad that you like it...73
Another great video! I'm going to have to watch it another 6 times for it all to sink in!
Another interesting video viewed, great job as usual Peter.
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.
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. :-)
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!
Hi Patrick, thanks for the feed-back glad that you like it. 73
This guy is next level technician...period prolly the best on entertainment
That harmonic suppression is beautiful at that output power level!
Right it is really not to bad. All the filtering is just working fine 73
Extremely thorough test, really learned a lot and enjoyed! Thanks - Lloyd W9NLA
Thank you Lloyd 73
Hello Peter!!!...Very nice work, I really enjoy watching your videos!!!
Good explanation of troubleshooting. Thanks for sharing your work. Impressive!
Thanks for feed-back and watching 73
I always like to keep an eye on you my friend to see what you are up to :) Another great job Peter.
Cheers
John
I'm always glad to see you here my friend! Thanks for watching Cheers
Ooo what fun. Looks like maybe an arc over from high SWR caused a thermal runaway. Great video!
Great diagnosis, it is too easy to rush through a repair, well done for checking the low pass filters. 73
Thanks for Feed-back 73
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
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
You do great work Sir enjoy viewing your videos and learn a few things too. Thanks for sharing.
Hi Wade, Thanks for watching. I'm glad that the videos are interesting to you. 73
Thank you for this interesting and detailed video. Great troubleshooting.👍
Very impressive work.
3:49 oh WOW!
Thank you for great videos!
I like your DCA55 component tester. It's really useful.
"Magic Smoke Escaped" I Subscribed and Hit the Bell the second I heard you say that :) . I personally have seen a 1 inch high flame come from one of those SMT ceramic capacitors; those little caps can do a lot of damage. You are an amazing technician and we are all blessed to watch you in action. God Bless You TRX ! 73 Lawrence VA7LTX
Thanks for sub!
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.
thanks trx bench i always learn from your videos keep up the good work
Thanks for your Feed-back. 73
Another great video Peter! Very well explained.
I liked your dummy load... I have a EKD-100 for restoring.73's
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
That is one bad to the bone amplifier! Very nice equipment there.
Great explanations and good job on the troubleshooting.
Thanks
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.
Really a Nice video again. Thank you and best regards Peter
Absolutely wonderful, entertaining and delightful. Glad to be a subscriber.
Thanks for the kind feed-back Mart! 73
Very concise and very detailed. A terrific video !!!!!!!!!!!!
Hi, glad to see you!! Hope you are okay. Thanks for watching and comment 73
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.
LOL yeah some seriously high RF :-) Thanks for stopping by Adam! Take care 73
@@oldjarhead386 yes, very appropriate question and he had not shown the same on the video 🙄
De VU2RZA
Excellent and informative. Thank you.
After going step by step watching this.... you did everything right. I suspect a roach climbed between that circuit and created a ground fault for a long enough period while the amp was not engaged on. But long enough to create a little mini heating element and the burn occurred. What I don't see in this circuit design is a fuse between the main PSU and this burnt circuit which would have blown at the current a roach would draw. The only flaw in the circuit design was lack of a fuse element after the main PSU to protect the entire system from fire hazard. I will be placing a correct fuse in my own system which is very much the same as this unit but half the output and of course 48 volts. Thank you for posting this video. It was very informative not only for repair study but concept design as well! Good job on the entire video and thank you. If it wasn't a roach then it may have been an arc caused by too much solder on the main (RED) wire that may have melted during or at the end of operation... then while the operator was asleep and the unit still powered... MAGIC SMOKE? He or she wakes up and suddenly the amp will not function.
LOL yeah may be...Thanks for feed back
Thanks for these vodeos Peter lots of good info here.
Glad that it is useful for you Grant. . Thanks for watching 73
The world needs more people like you! Genius
Thanks Jim!
Wonderful amp quality
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
Thank you Leo! 73
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.
Very thorough testing very impressive Peter, as usual 73's VK6NJP
Yeah a lot of work to make sure that the PA is working...Thanks for watching Jim 73
thumbs up man, i want one of those 10 kw tube amplifiers for broadcasting ;)
Great video
thank you Peter!
Thanks for watching Dennis! 73
This is spectacular!👍😃
Another great lesson, thanks Peter. 73s de IW0HEX Pasquale
Glad that you like it Pasquale. Thanks for stopping by 73
É bonito ver um verdadeiro técnico!!
Thank you 73
Very much enjoyed your video thank you regards steve
Thanks for watching and feed-back 73
SWR protection circuit was out of adjustment, great job and 73! YO5CAT
Thanks for fed-back 73
schönes Output Signal.. sehr nice
73
Danke fuer deine video! Sehr gut! Danke schön.
Thanks for watching Vielen Dank und schöne Grüße
73
Thanks for sharing.
Thanks for watching! All the best and Cheers
Peter, nice one again.Big thumbs up.Well that kind of pots are really bad, I've lot's of problems with them, since that I always use Bourns pots one critical circuits.The fault on the pot could be related to heat that it get's from the RF board, and with time it's gone deteriorate till complete failure.Again good job.
Hi Nuno, thanks for feed-back. Well there are a lot of crappy pots on the market and the Bourns really first class but the used are already precision pots and not that bad. But the permanent heat is a problem to all components..Again thanks for watching 73
Those FETs are huge!
and cost a bug of money
Excellent! very nice!
Thanks for watching 73
Great video - very instructive. 73 from VK6HIL
Thanks for feed back 73
Great repair. All that power output would make me real nervous though.
LOL no fears here.. Thanks for watching 73
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.
Hi Steve, thanks for feed-back! All the best and 73
Interesting and informative video Peter.
73 de Malcolm M6MYB
Thank you Malcolm 73
Nice video!
I really would like to take a look inside that 1200W RFT dummy load.
Thanks, 73.
Hi, well there is really nothing exited to find only the full capsuled dummy and rough fans.. Thanks for watching 73
good job and nice video
Thank you
Great video and some awesome test equipment.
I thoroughly enjoyed that very well explained test procedure.
I could be wrong but I don't think you reset the Pot to trigger the Thyristor for the AFP LED after turning it fully clockwise.
Thank you
One hell of a way to keep the shack warm. 73
LOL yes that is right.. 73's
Very good explanations. Networkanalyzer: would be interesting to know what komponents you need for it.
Hi, thank you! You find all about the network-analyser in video #77. 73's
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!
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
very informative
EXCELLENT !!!
Thank you
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.
Excellent video as usual. This channel recommended by Mr. Carlson's Lab.
Hi Andrew thanks for watching and feed-back. Paul is a very nice person!! All the best Cheers
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.
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
very nice
those mosfets are super tough, good to 50:1 swr at full load.
Yeah this MOS-Fets are monsters :-) 73
very nice 🙂
Another great job Peter. ... sweet amp!!!
Thank you Jeff 73
Can this transmitter handle being keyed down around the clock?
you could scroll around the 12M band to see where exactly that filter is tuned and then possibly re-tune it.
Enjoy you videos Peter. Would you consider a video on the Rhode & Schwarz CMT setup and use? Thank you!
Hi, thanks for stopping by. Well yes hat video topic is already on the list only time is the issue.. Cheers.
I Have watched your video very good what software did you use to measure output power at the end thank you
I didn't see if you adjusted the SWR protection circuit with high power. Did you leave it at the sensitive setting from earlier?
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.
Very nice video. 73. AB2ES/7 in Oregon USA
Thank you Bill 73
Sir Have u ever repaired
Co2 laser RF Amplifier. thx
Peter,
Another nice video. Two thumbs up. :-)
WB3BJU
Thank you Donald! 73's
Great video!! Maybe I missed it but did you check the SWR protection circuit after you repaired the amp?
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
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?
Irish Vikin
Hi, nice video! Question - where from did you get that new board for such old PA? Where from did you knew what bias current must be?
Hi, as I said in the video the PA is based on a application note from Motorola, there you find he suggested Bias. Parts can still purchased here www.communication-concepts.com/ar347/ Hope that helps . Thanks for watching 73
Master Repair. All case are tested.
Danke Karsten
Hi Peter, Another great repair job done there. I had to see the funny side to that great big hole in the filter bord. It reminded me of a comedy record that was out some years back and a bed sheet gets ripped open by someones feet going through the sheet. Out comes a voice" Who look at that hole". You would have to have heard the record to see the funny side to it. Not funny would have been the cost if the power Mosfets had blown. Any how a good repair job done Peter. 73 de John - G0WXU.
LOL yeah very good should look out for the record...Yes the IC is very pricey but we were lucky. Thanks for watching 73