How to repair a smoking Fender 5F2 Princeton vintage tube guitar amp

Here is a close to live repair demo on a very vintage Fender Princeton. Initially I was going to present this on SKYPE, therefore camera shots were limited. Later, I decided to do close-ups (gave up on the Skype), and show you better details of the troubleshooting and component replacement. So, you will get a better idea of my troubleshooting, failures/feats. This amp came from Hawaii, so shipping will be higher than the repair cost! I really enjoyed this repair. Special thanks to Chesney on the opening scene, spraying me down with the unexpected sneeze!

[@rciancia]

Terry, this is one of the best videos you have done because you are troubleshooting live and not telling us what you did but showing us. I learned just today that there is a huge difference between troubleshooting and shotgunning..... good stuff bro

[@d-labelectronics]

Thanks man, I really do appreciate your support

[@StuffBudDuz]

@@d-labelectronics Seconding Ron's comment. More like this, please. Great stuff! Thank you, Terry.

[@Mojoman57]

"Be wary of tubes that arrive with an amp," -Uncle Doug 2019

[@julesl6910]

"If this van is a rockin, don't come a knockin' " - Uncle Doug 1985

[@sski]

I love watching you work. You remind me of my father, Master Sargent Stanley Sikorski, Sr. USAF, who was a highly skilled electrical engineer and teacher at Chanute AFB for much of his career. He's no longer with us now, but watching you brings back memories of his methods and skills when he was working around the home shop.

[@rodleger7132]

Terry, please keep the videos coming along with your explaining along the way. This helps tying in theory with real world examples.

[@MuscleDad420]

RIP Aspen Pittman. Have the very same edition of the Tube Amp Book. Aspen signed it "Keep your pins straight, your sockets tight and never lose your bias." Great advice. Btw the owner's story mentioning "Hollywood" and "GIT" raise alarm bells. This was likely a tweed Princeton kept in one of the study rooms at the second Guitar Institute location in Gower Gulch.

[@philnaylor1979]

Thank you for sharing this. It's a diagnosis masterclass !

[@waynekozak1462]

Terry, I love all of your videos, but this was ESPECIALLY valuable because it was in real time but because things were not straightforward. thats how it is, in real life. Whenever I go to repair something, there are always things that dont conform to spec. thank you very much! Wayne

[@iggyward]

That was the best half hour I've had in a long time!!

[@simonkormendy849]

When the output transformer of a tube push-pull power amp stage is connected-up improperly, it basically transforms the power amp into an even more powerful oscillator due to the negative feedback network becoming a positive feedback network.

[@robinr.2233]

Cool that your story time reading is from Aspen Pittman's great book "The Tube Amp Book". He passed away just a week ago. RIP Aspen. G.I.T. 1981, is that Guitar Institute of Technology? Established in 1977 by guitar great Howard Roberts and Pat Hicks. It's now called Musician's Institute (MI) and has contributed to the education of many players over the years.

[@firemanmick]

It is a pleasure to listen to a person who is experienced and knowledgeable in regards to amps rather than the self appointed "experts" who dish out technical gems of knowledge that, with absolutely no technical background, they have gleaned from other so called "experts" with equally limited tecnical knowledge. Please keep these videos coming - they are awesome!

[@martinreid1740]

Really enjoyed watching you troubleshooting this. Thanks for sharing your knowledge. I have learned so much from you.

[@rachelcampanella5426]

I think this is the best vid you have done, Terry. Excellent stuff! I really like the way you showed the logical process of troubleshooting the various problems this amp had. Thanks so much for sharing it!! Cheers, Simon

[@mattdixon333]

Terry, I loved the long video of you talking through the faults and troubleshooting live. Very, very good! I am looking forward to more. Greetings from sunny Australia!

[@preiter20]

Great troubleshooting Terry! I still have so much to learn.

[@stupiddooley2140]

The F&T caps are great, have them in my '66 VibroChamp and '64 BandMaster.

[@batman387]

I learn a lot from your videos Mr. T. Thanks for sharing your knowledge. LOVE the doggie shots. Emi’s too! 😁

[@travistalkington9297]

My first amp build was a tweed 5f2a Princeton from looking at a book and layout. Absolutely love this amp! Love watching this video

[@julesl6910]

Best intro ever filmed

[@waskele.wabbit717]

Don't understand most of what you are doing but I somehow find it fascinating. I wish you were my neighbor I could keep you busy for a while

[@julesl6910]

Is that a sexual comment?

[@deepwater2652]

Loved the canine clip! I've got one of those "sneezers" too!

[@psyolent.]

that was a GREAT video thanks for walking through your diagnosis - fascinating to see

[@simonspeaker]

I know lot of technician, but you are BY VERY FAR, the best of the best!

[@raymondcote6669]

Although our trouble shooting is different, outcome is positive. I enjoyed your video even though my radios are larger and more complicated as i align and cal mostly the R388 thru R-391 Collins. Thanks for what you do. Very informative

[@petercornell2002]

Excellent vid Terry, thanks.

[@Generalterz]

Thanks a lot for that video. Even if I don't mess with amps myself (lack of knowledge) it helps me to understand the very basics about how amps work.

[@DennisMurphey]

Very useful video you are really educating us on the realities of Tube amp Diagnosis. I had a nice old Scope, but sold it. Now i wish i had it back so i could see the sound wave. Thank You, Dennis

[@eduardpascal7229]

Great job Sir, U're one of the Best on KZbin. Greatings from Romania!

[@bruceferrero8178]

Nice job man! Enjoyed the class.

[@JammyCrackcorn]

Great Video!! Loved this one!!

[@waynewayne3709]

There's a trusty bottle of thinking juice on the bench... Class!

[@apollorobb]

Crazy how you can hear the oscillation on the video from the output transformer .great Video Terry 73's KC5SRG

[@witeshade]

It's actually pretty normal, although usually on higher power amps. Output transformers actually make quite a lot of noise, it's just that you don't normally hear it at all because the speaker is much louder.

[@scottbc31h22]

Did you notice the shape of the waveform. Looked like a half square/half sine wave. Tells me it's not the same as the input signal.

[@velvetsound]

Thanks for this video - it helped me solve a phase based feedback problem with my new JTM45 build.

[@charlesmatthias9459]

Thanks',Terry,great video!Nice watching you trouble-shoot live! Really interesting.It is obvious that you have seen some of these problems' before! : )

[@daveogarf]

I LOVE a happy ending, Terry!

[@garybevis8691]

As always love to watch your videos Terry. I like the way you cruise thru the circuit, as to say, fun...I have a Tek 922 scope that I converted to a curve tracer, a la Mr. Carlson's Lab. I love that little scope too, BTW. Gary

[@Burgoseletronica05]

Nice video my collegue of profession. Regards from Brazil.

[@caspianwendell]

Now that’s how you make a video, great job!!!

[@peteleoni9665]

Now *this* is a very valid lesson!!! This is real and it shows!

[@jimgiordano8218]

This was a good one, lots of issues. Great job.

[@jakeblues3676]

You’re the best Terry, you continue to remind me of my buddy and mentor George Runyan WB6YEC you also can fix anything and a real diagnostic and trouble shooter. Also a fellow AMer 3870Khz..73’s and Thank You! -.. . .- .- -.... .... -.- -.-

[@GTEK-LAB-TECHNOLOGIES]

Congratulations, you are a colleague of mine, I follow you from Naples (Italy). Heartfelt greetings.

[@roberthurless4615]

Excellent video Terry. And btw, I love big dogs. I have two at the moment, and one medium size. Lol

[@GL64]

Great video. Very informative. More diagnosis vids please!

[@edwardhannigan6324]

Great repair and so informative for us 'newbies'..Thank you for sharing your knowledge..Ed...U.K..😊

[@8xlaxx]

Labrador Retrievers are the best,...so much personality these big, ole galoots! Great video Terry.

[@waynewayne3709]

I've the very same valve amp book 📖 plenty of useful information in there. Very detailed repair work from D lab..

[@raffyzoo2130]

oh, the drama....more please

[@diceman220]

Nice job. I have a 1960 Princeton. Love that amp.

[@jamestaylor3500]

diceman220 man , I also had one not quite as old that I lost when a tornado hit our town,,,,, I really miss that sweet sounding amp! I'm not a terribly religious man but I've been on my knees many nights thanking God no one in my family was hurt

[@josephmartinez3851]

I just want to say I have learned much from D-lab and Uncle Doug. I think I noticed you didn't have a good connection when checking the filter caps at 5:00 with the test leads. Good video, I'm just happy I spotted something or maybe I didn't but still had an idea that was generated from all your great videos...

[@bconman]

Dude, you are the master.

[@0MyWay01]

As much as I love the 2 kHz sine wave test tone. You should have your guitar buddy record some riffs on some recording medium preferably a looping pedal So us guitar players can hear What these amps sound like.

[@hallanvaara6106]

Thanks for an awesome video! Maybe you could have a guitar with an open tuning and then just strum the open strings for a few times? We would love to hear what these beautiful amps sound like.

[@daleburrell6273]

...well, "ya can't please EVERYBODY!!"

[@0MyWay01]

@@daleburrell6273 No but you can try!(D-Lab does a great job) A successful KZbin channel IS an attempt to please everybody as measured by the number of subscribers. I humbly offered a suggestion. Love this channel even built a D-lab designed 6f6 amplifier from an old Regency police radio. Sounds great wide open through a Marshal 4x12 cab.

[@lincolnmicrophonellc]

Nice work! Clever to pull the feedback, I'll pocket that one.

[@whatsstefon]

When I replaced my friends OT on his Bassman so we could use different cabinets with different resistance, I fired it up, and it was that one time I didn’t bother connecting a dummy load and scope. Nah, I went straight to the speaker. That’s the first and last time I’ll ever do that. The level of feedback coming through the amp was insane. Made me jump. In your video, I could hear that tone coming through the dummy load and knew that’s what it was immediately. It’s a familiar and traumatic sound for me, ahah haha haha.

[@infectionsman]

I repaired an amp that always had a pleasant volume to it. Turns out the OT had a slight short on the primary that caused it to attenuate the volume kind of like the "Cerrem's mod". After I rewound the transformer I hooked it up and just casually did the old Pete Townsend windmill chord strike. I swear the amp was 5x as loud nearly blew my pants off and scared the crap out of me!

[@Barracuda48082]

I was guestimating your next statement on the oscillation..rev polarity or out of phase audio xfrmr...great work.. The ole gray sponge here still can recall somethings..hihi. ..about my antique tube portable am radio.. 110 vac or 10 eveready 9 v . heirloom from 2 gens back..care to go thru it and swap the buzz for music?

[@kc9kepextra460]

Terry, just stumbled on your video! Great stuff, and it’s appreciated. Here’s a great question for you, if you please .. How do you calculate your charge for such a repair? Gracias!

[@paulmoreton3083]

Terry this was an excellent video as ever, can't help thinking if you had hit the red vino at the start you may have solved it even faster! Loving your work though and great to see a true live master in action! Off for a vino myself now. Cheers Paul in the UK

[@d-labelectronics]

Thank you my friend. Im attempting to up the quality of the presentations

[@motorjock0478]

Hey Terry, I enjoy watching your video's. I wish I had half as much knowledge as you have about electronics. Do you have any update on your attempt to obtain the property next door? A couple of years ago, I purchased a 1996 Fender 2x12" Hot Rod DeVille tube amp. and upon removing the back panel, I could see that the original filter caps were still in the amp. I didn't want to remove the circuit board, so I cut-out the old caps and left the original wires, and soldered the new F&T caps to them. That seemed to fix the issue of excessive hum on the normal channel, but when I switch to the high-gain channel, I am still getting way too much hum/buzz. Do you have any suggestions for what I should do next to hopefully fix this issue? The only test equipment I have is a digital multi-meter, and a little audio probe I made from a Radio Shack mini amplifier speaker.

[@Nirky]

Nice story, love that playful snow pig.

[@TheJostenso22]

I was lucky enough to get the feedback loop wired up backwards on both of my custom builds. Man does it ever make a squeal if you have a speaker hooked up.

[@johnsimms3957]

Excellent!

[@choctawhatcheekid309]

I always add some series resistance in the filament chain to lower that voltage to 6.3 volts on my vintage amps. It also reduces surge current at start up. If you have ever watched Mr. Carlson's Lab video about how much current those filaments draw at start up. It is almost 2 amps per 12AX7 tube lot of stress on that power transformer.

[@jerkerfridh8189]

Great hands-on troubleshooting! Thanks to You and M.Caldeira I've revived two radios with cap issues. However, I was accompanied by a couple of beers and a cat, do You think I should move up to red wine and a dog before having a go at my guitaramps? Keep up the good work Terry! Cheers from Sweden!

[@dwebster50]

Terry , thanks for posting ....my interest in building a 6v6 push pull is gaining interest. You dogwood videos and generally you make it fun Alberta Dave

[@Davesintexas]

WONDERING about the three wire connection? I used your method of wiring till I saw the Hot Lead being wired to the On/Off Switch and then Back to the Fuse. I heard that if wired as I have always wired that if the amp goes down and the fuse isnt blown someone may try to change the fuse and get zapped if the amp is still plugged into power, What are your thoughts?

[@giovanni4070]

A regular Sherlock Holmes, master of deduction and solver of riddles.

[@tubefixxer]

Fantastic troubleshooting Terry. WA4VDB

[@doobymaster6997]

Just a comment about those green/yellow jumper leads. I’ve had issues in the past ‘cause they’re usually just crimped clips to thin stranded copper (usually through the vinyl insulation). Some don’t make contact, so always a good idea to peel back the insulation on the clips and solder them (then you don’t have to worry about a possible bad connection there).

[@Robert-Smith]

I know this is an older video but could you tell me what the difference between the 5f1 circuit and the 5f2 are. Thank you love your videos big fan thank you.

[@Robert-Smith]

Hi Terry I really like your videos and have learned a lot thank you. I have a question about filament voltage when testing without tubes. When testing the instructions say you should get around 7.5V but I am only getting 3.5V could you please suggest what might be happening here again thank you very much.

[@Robert-Smith]

Ok I think I figured it out myself I was using chasis ground and checking the pin when I was supposed to measure across the pins.

[@Wim37u]

Thanks for sharing.

[@richardleerodgers5303]

Great Troubleshooting

[@waynewayne3709]

I've got that vavle book in my pile of books.. Very good.

[@knottreel]

Very likely the cleanest bench in the civilized word, with one possible exception being Mr. Carlson's lab.

[@f.k.burnham8491]

Great repair video. I do need to ask- why did you leave the old blue paper caps in the amp instead of replacing them? Almost all of them I find are bad.

[@d-labelectronics]

The owner wanted to maintain the tone quality of the amp. I measured the coupling caps for leakage, look fine

[@thierrycaudron3266]

Bravo très beau travail et merci pour ton aide bonjour de France cordialement Thierry

[@fernandodossantosmusica]

Super Nice job

[@DeadKoby]

I use F&T caps, as well as CE Dist house. Some swear by Sprague Atoms... but I can't stomach the price. Any thoughts?

[@infectionsman]

F&T are great, no need to break the bank

[@dhpbear2]

I've viewed up to 18:45. My guess is the polarity of the replaced output transformer was reversed!

[@TheDesertRat31]

Regarding modern wall voltage. I used a 12v center tapped transformer as a bucking transformer to create vintage voltages. It can give me line voltage, and then I can switch it to go be me either ~110vac (tweed era voltage) or ~117vac (blackface era voltage) depending on what the wall is giving.

[@andysparks7381]

what do you use for a dummy load when you’re testing an amp?

[@RobertKohut]

Nice!!

[@davidsigglekow1349]

Your too good for your own good lol ! Great work sir!

[@rodleger7132]

Love that Dog!

[@sounddesignerinc.1770]

Your a genius!

[@donaldfisher8556]

Terry is a really enjoyable video. Hey tried to donate to your channel but hit a wall when I hit the donate button. Could you confirm it's working. I'm hoping the issue isn't the Canadian money LOL.

[@thomasseaton8320]

Can you recommend a place to buy good sockets for Fender style amps online? I built a Stewmac Princeton kit and the sockets are trash.

[@evananderson8452]

Another great job. A shame you had no wine.

[@jvin248]

I did a google on 'Fender Princeton Mods' and a quick scan it appears a couple of those items you found different than the print lined up with one or more mods. Might be a good giggle if you do your own google knowing what's in that amp.

[@mr.selfdestruct2917]

I've been told to only use dummy loads if there is a signal is that true can I power up an amp without dummy loads if there is no signal?

[@W4TRI]

Would you consider working on a modern radio? I have a Yaesu FT-817 that needs a final board replaced.

[@d-labelectronics]

Hello, sorry my friend, I can barely keep up with current repairs, several months behind

[@Dmcinc]

You are Master!

[@robertedwards3147]

I like using vintage test gear on vintage amps/ radios etc

[@fabinhoosmar]

Esses capacitores de amplificadores e rádios antigos, é bom trocar, mas vale sua aula de conhecimento para os novos

[@timmitchell8524]

I noticed you did not dummy load speaker output?

[@Periskop1]

399 volts at idle while normal for push pull Princetons, is way too high for tweed Princetons in my experience.Also too much filtering may seem okay technically but it changes the tone character of these amps,making them feel/sound tighter which in a way is not bad but just different sounding than the original circuit with less filtering.Also, spec sheets for 5y3 rectifier tube has 32uF as maximum allowed capacitance.Now there are two paralled 22uF caps giving around 44uf combined capacitance for the 5y3.

[@Barracuda48082]

Oh, the book said fixed with wine..must have evaporated.. 😋

[@kornami8678]

If it utilizes negative feedback and the output transformer was replaced, the leads of the output transformer are reversed. Just flip the wires on the primary. What you had with the wrong transformer connections was a positive feedback circuit which is another name for an oscillator. And sure enough you had a square wave oscillator.

[@blueribb99]

Did you check or replace the 10K resistor after it had 200+ volts across it ? I know you cut power pretty fast but 200+ volts across a 10K resistor, means that 1/2 or 1 watt resistor was handling over 4 watts for a short time. E squared over R = Power. Nice fix by the way.

[@donaldfilbert4832]

I know !! I worried about that too ! Plus - that is probably where the smoke came from - and that can't be good for it !! ;)

[@blueribb99]

Metal Oxide resistors have small vent holes on the ends as far as I remember and handle surges much better. The 1-watt metal oxide resistors are about the same size as the old carbon resistors. Aren't the metal oxide resistors usually blue in color ? (his wasn't)

[@bigmac965]

Around 6:25 what's all that background racket? Sounds like people are rioting outside your door! Are you safe in there?

[@d-labelectronics]

There was football practice in the school yard behind my house, Yes, I caught that too!