#285

[@bblod4896]

I have discovered applying low temperature solder to those power MOSFETs first, then applying heat makes removal of the transistor a breeze (easy). Thanks for the video, Merry Christmas and Happy New Year to you and your family Peter.

[@M0UAW_IO83]

Bit of hot air to pre-warm the board up to around 120C helps a lot especially when you mix in the low melt solder, it's really good for reworking irreplaceable vintage computer boards too.

[@bblod4896]

@@M0UAW_IO83 Yep.

[@8du]

@@bblod4896 I recently acquired some " CHIPQUIK ". I haven't tried it yet but it's supposed to be some good stuff. It should be considering the cost. 73

[@jimgiordano8218]

Another excellent video. I learn so much from you. Thank you Peter.

[@8du]

Nice to see you again Peter. Thanks for sharing another video. Merry Christmas to you and yours

[@TRXLab]

Merry X-Mas

[@dougrea8260]

I really like how concise you are in your descriptions. You are brilliant. I really like your videos. Thanks.

[@TRXLab]

Thank you very much appreciated..

[@grandpaandlucas7054]

your to good Peter you never create any sparks or smoke and you never get burnt or electrocuted. love the video clips. happy new year best 73.

[@TRXLab]

lol no I'm not Electrobuuum ;-)

[@ninaevans4501]

To Peter and Family, WISHING YOU ALL A VERY MERRY CHRISTMAS AND PROSPEROUS NEW YEAR. From Wayne, Nina and Barbara (Waynes mum). Love and respect to you all from Ipswich, Suffolk, UK. 73's good buddy!! ❤️❤️❤️❤️❤️❌️❌️❌️❌️❌️🎄🎄🎄🎄🎄🐧🐧🐧👍👍👍👍🇬🇧🇬🇧🇬🇧🇩🇪🇩🇪🇩🇪

[@TRXLab]

Dear Nina, Wayne and of course Barbara! Merry Christmas and a healthy new Year to all of you. Have a nice season holiday. 73 Peter

[@ninaevans4501]

Wow!!!!! I now have one of those tv/magnifier machines. So my other half (Nina) can now observe my technical brilliance first hand 🫣🫣😁😁😁 I will now drink some good German lager, and wish a toast to better things to come. 73's Good Buddy Wayne & Nina (Ipswich, Suffolk, UK) 🍺🍺🍺🍺🍺🍺🍺🍺🍺🍺❤️❤️❤️🇩🇪🇩🇪🇩🇪🇩🇪🇬🇧🇬🇧🇬🇧🇬🇧

[@joelkist6493]

Fabulous teacher... thanks for your video's.

[@Derrick6162]

Enjoyed the hunt. You are a great technician. ❤ Thanks for sharing. 👍 👍

[@TRXLab]

thank you

[@Derrick6162]

@@TRXLab Happy Holidays

[@mikefinn2101]

Thanks peter for a real nice educational video your very kind and very helpful and truly a pleasure to watch. Love to enjoy your channel I will be looking forward to your next videos. Merry Christmas and Happy New Year. Take care my friend 73s Mike

[@izzzzzz6]

I like those snap on / clip on adapters for the DMM probes! When you did the idle current on the last two transistors (600mA then 1.2A) Are the test leads still connected to the same test point? Oh. I see it @28:37 And It will be easier from the service manual. Thanks Too true about shielding in these radios, people may experience HF on the mic or perhaps even damaged components. I've heard some of the grounding points have board varnish over the connection points on some of these radios (poor production on some of them).

[@lisakay2076]

I love this guy he is brilliant very thorough and extremely intelligent. I would let him fix my radio anytime as i know it would be 100%> the sherlock of radio fixing

[@TRXLab]

Thank you, very much appreciated !

[@Chicoelwahsh]

Amazing thank you for the great work .

[@4nk8r]

Another great year on content . Looking forward the next year . "Let's C what we can do))" happy holidays 🎉

[@boxingday11]

Thanks Peter , have a good Christmas, and a peaceful new year.👍🏻🤝

[@TRXLab]

Happy X-Mas!

[@GoodLuckBP]

I have learned a lot from your videos. Thank you. One of the things I have learned is I can not work on these micro circuits with my hands! Thanks for keeping our radios going!

[@karlfell3768]

I have done this on 3 radios in the lst 18 months. Never any issues with bias settings, just a very common failure point.

[@adamap2796]

Common failure point on the FT991A ?

[@redacted2763]

@@adamap2796 Yes, can confirm that my 991A encountered the same failure.

[@TRXLab]

Unfortunately, some of the little pesky pots are bad and thus misaligned...

[@adamap2796]

Very enjoyable video Peter. I own an FT991A, I wonder if this will prove to be a common failure of the radio.

[@redacted2763]

I had the same failure on my 991.

[@TRXLab]

It is not a common failure but some bad pesky potentiometer causing it.

[@adamap2796]

@@TRXLab 👍

[@Roberto.P]

Great teacher! Thanks for sharing!

[@wolfhawg]

Hi Peter. Thanks for another interesting video. Merry Christmas. 73s.

[@TRXLab]

Merry X-Mas

[@CHUCK.H57]

Thank YOU ! your videos are always very informative and clearly explained. Much appreciated.. Chuck, ND5CH

[@TRXLab]

Thank you Chuck!

[@iw0hex]

Antoher great repair Peter, thanks for sharing. Happy Christmas time my dear friend. 73s Pasquale IW0HEX

[@TRXLab]

Thank you, Pasquale, and happy X-Mas to you and yours! 73

[@michaelclutton8446]

Thanks for another very interesting video

[@kentaylor6563]

Hi Peter is this a common foult ? I have a ft991a with no op. On VHF and UHF. Still under warranty.

[@hancecrawford]

Merry Christmas Peter and family and Happy New for 2024 thanks for another interesting video great repair, Peter strange the both 47 Ohm were gone on both driver mosfets peter applying that temperature grease is very important

[@TRXLab]

Merry X-Mas

[@klartajanssen4368]

Hi, just Gavin Problems with my 991a. There was a burning smell yesterday. And now, in the HF bands I only have 50 watt. So I am wondering what a repair as shown in the video would cost.

[@TheGmr140]

Nice video, nice lab, and repair 😊

[@dondonaldson1684]

Those PA's are very hard to change out. Great job Peter, and excellent job with alignnent. Those potentiometers are terrible. If the radio is bumped or knocked, the alignment can easily be messed up. Glad you put a precision pot in place.

[@bearofbarham]

Hi I have a Yaesu 991A, and it works, apart from transmitting, it creates a carrier but no audio at all on any bands, any idea what might be wrong with it, I also have an Icom 725 which is 1mhz off frequency, is there an easy way to bring it back inline, many thanks, Excellent videos and skills.

[@josegermanparra6064]

Many thanks for this excellent video. Could you give more details on the R&S testing unit you used ?

[@TRXLab]

well, a normal CMS52 radio tester..

[@w.rustylane5650]

I have the Yaesu FT-991a and I hope it does not screw up as it's less than a year old. I've heard about transmitting on another radio that's in close proximity to the 991a will cause a resistor to burn out. So I make sure I don't use my 2 meter radio when the 991a is on. I never have both radios on at the same time even though they are less than a foot apart. So far so good. I have a Ham friend that transmitted on a radio next to his 991a and it blew out a fuse in the 991a. I'm always careful about that. Cheers from eastern TN

[@TRXLab]

if you transmit into a radio next to you with some power, it definitely burns your front end, no matter what brand it is...

[@la7yka]

As I can see on the VHF/UHF PCB, there is a reflection bridge between the antenna connector and the amplifier section. I presume if the amplifier is using fold-back, there should not be possible to destroy the final dual MOSFET due to high SWR. Any points of view with respect to that?

[@che59v]

Thank you for shearing the information, Merry Xmas to you.

[@TRXLab]

Merry X-Mas

[@ThaVoodoo1]

Great repair video. Can a high VSWR cause the transistor to fail?.

[@TRXLab]

only under certain seldom circumstances

[@jimjaeger8968]

I've got a problem with that same board. Low SWR, read internally using the radio's meter. It's hooked up to a test load so it is exactly 50 Ohms. The SWR reads 3.1 at 50 watts. It reads about 2 to 1 using 25 watts. I had to send it back to the factory. It is essentially a new radio. I just got it back from service too. They replaced both HF finals. It didn't seem to have this SWR problem when I sent it in. No explanation how a new radio could have bad finals. Now after watching this video I am not so certain the two problems are related. If I caused it I wish I know what I did. I have two of these radios. The other one was in the shop for repairs too. Luckily it was covered under warranty. I was never informed of the problem's cause. I did ask them why it failed and what failed but got no answer. I really like the features of this radio. I'm not so sure about the quality of build and component design though. When they work, they work well. When you get so many failures from a new radio one has to wonder.

[@sw6188]

Cost cutting. Even some 'big' manufacturers like Yaesu are doing it. I suspect the market for amateur radio is declining so makers are forced to cut costs to stay in business. A high VSWR as shown on the radio may be due to a problem with the reflectometer. Start by checking the components in that section. If they are Ok then it's time to look at voltages from that circuit and see how they stack up. Also look at whatever is in the RF path from the reflectometer to the antenna connector.

[@TRXLab]

Sometimes the bias gets to high due to bad potentiometers..

[@sw6188]

@@TRXLab Not something I had considered. Can you explain how that would affect the VSWR reading on the radio?

[@t1d100]

What are those unique probes/test leads, please? I checked the comments, but didn't see them listed. Thanks.

[@TRXLab]

which one do you mean?

[@t1d100]

@@TRXLab It's the meter probes that you used for the entire video, mostly... Red and black... On creme/tan... I didn't think that they look like Probe Master, but they do look high-end... They have right angle plugs... And they accept unique long reach pincer adapters. I wondered what those are, too. Thanks for the extra effort to reply and chase it down...

[@t1d100]

See @ 5:58.

[@TRXLab]

@@t1d100 well the test leads are originally Agilent/ Keysight and the Probes are Hirschmann www.buerklin.com/en/p/hirschmann-test-measurement/test-leads-and-test-probes/pruef-2610-ft-rt/35F1186/?segment=b2c

[@TRXLab]

@@t1d100 well the leads are originally Agilent/ Keysight and the probes are Hirschmann www.buerklin.com/en/p/hirschmann-test-measurement/test-leads-and-test-probes/pruef-2610-ft-rt/35F1186/?segment=b2c

[@notfallmed]

Hello Peter & thank you 73 🙂

[@TRXLab]

Danke Peter

[@MK2Dirtbag]

Looks like the same final as in the FTM-400, but much harder to replace...😳

[@redacted2763]

Bingo!

[@TheMisterNomad]

Your video is enough to convince me I don't want to attempt to fix anything INSIDE my FT-991A. I need to have the Silicon Labs CP2105 chip replaced on my main board as my radio is out of warranty. Does anybody know a facility in the U.S. that can do a hot air surface mount chip replacement?

[@ouijim]

Another outstanding repair. Thank You. What was actual cause of failure? I suppose faulty components or procedure during build and assembly. Also some amateur radio operators run radios at maximum power always disregarding duty cycle limitation. Wish more care was taken at factory as radio at $1200 US is major investment for most of us ; )

[@TRXLab]

Bias to high

[@xxdarkehammerxx6121]

How can I contact this guy for repair job?

[@jean-francoisgrun7524]

Awesome video as always! They should definitely put better potentiometers at the factory. Thank you and merry Christmas! 73 de VE2VHE

[@TRXLab]

Merry X-MAs

[@deytalima4920]

hi peter, ..hope you are healthy and happy..i have a yaesu FT847 radio, but it can't transmit on 143,000mhz..hope you can show me that way🙏😇

[@sw6188]

I see on the Siglent bench meter "DC Current". Direct current current. 😂

[@TRXLab]

lol

[@pixeluser175]

The 'A' in '991A' means 'Again'.

[@charliem.9998]

Peter is our man ... thank you so much ... Fröhliche Weihnachten für Dich und Deine Familie ... 73s de DL6RDE / AA1KD, Charlie

[@TRXLab]

Vielen Dank Charlie für die Treue! Frohe Weihnacht!

[@stylerxxl1]

Ich habe bei meinem 991a auch ein merkwürdiges Problem - UKW klappt 1a (dafür habe ich ihn immer benutzt). Auf Kurzwelle in SSB kommt nach etwa 2 Min. Betrieb keine Leistung mehr aus dem TRX .. sehr unangenehm - kann ihn auf KW nicht mehr nutzen ... 73s de DL9HD

[@TRXLab]

das kann leider verschiedene Ursachen haben..

[@radioholicy]

oooh noooo! my radio... now i'm affraid

[@TRXLab]

lol

[@rubusroo68]

mini volcanoes on smd components never good news lol

[@KevinBasilMagnus-sy7rm]

GENIUS 🎉 JUST GENIUS🎉 Thankyou. 9V1KM KK7QGL Singapore

[@TRXLab]

Thank you for the honor!