How to repair fix Fender Champ 5f2 tube guitar amp noise by D-lab electronics

This amp arrived via mail for repair. It was a recent boutique amp build. Obviously, it did not go well. There were a few issues causing noise/distortion. D-lab to the rescue. A great repair. I hope that the info presented will assist you if you are building such an amp.

[@anthonybeers]

I know this is not popular but I am so glad that I get to use surface mount technology and 4 layer boards with grounding and power planes when I design circuits.

[@geoffrobson2493]

You're videos are fantastic. I have ZERO electronic experience, and I have decided to jump in and build a clone of a 5F1 champ. Seeing your videos helps clear up some questions and give me an idea of how to behave around and handle electronics safely.

[@rciancia]

Well done Terry. A great way to underscore the importance of proper lead dress and other nuggets :)

[@nine-graves]

Nice troubleshooting and effective fixes you did there! Thanks for the clear explanations and all of your hard work besides the repairs (filming, video editing, the cobbler appearance, multiple noise tests, tips here and there, etc.) Cheers mate!

[@yrulooknatme]

the mystery resistor is uncovered... I bet chico thought he was pullin a fast one... awesome to follow your logic....you make it look so easy....

[@TheRadioShop]

Terry that one was a mess!. Good job at running the cobbler off. Thumbs up

[@samuelvargas8344]

Man I wish I could become an apprentice/intern for a summer at this shop. Fantastic work!

[@MichaelLloyd]

I think the guy that built the amp needs to watch the D=lab channel on KZbin

[@leewarren]

Nice job! Thanks for the clear explanations and thoughtful solutions.

[@djfrank59]

It's sometimes amazing how a simple build could turn into a disaster LOL :) another great video!

[@giutarSan1]

Great work, I especially like the "Cobbler" scenes. Lol

[@murphdawg4414]

Super super informative I'm about to attempt same build thank you so much for your tips and Intel it comes easy to understand and clear.

[@charlesmatthias9459]

Great stuff,Terry! I learn a lot from you about tube amps' ! finding faults' in the circuits' and up-grading for (Noiseless) performance.Thanks' again! : )

[@KleyDeJong]

Awesome video!

[@imasubtech6389]

Another great vid Terry! I've got a 5F2 on my bench right now that looks like it was built by the same guy that built yours. Thanks for taking the time to record, explain, and post the video. Cheers!

[@d-labelectronics]

Roger that, good luck with it

[@nymsmacgregor7232]

Great videos, Terry...!! Nyms

[@smstiao-tecnologia]

Hi Tery, good repair and good garden !

[@pumpdumpster]

Thx, great video and explanations!

[@startend7196]

Awesome, very informative video.

[@subcinco]

Dlab you crazy. I'm glad you're in my life

[@LincolnFStern]

You should totally do a speaker hooked up test of the bad versus good 12ax7s. Great vid.

[@overlook77]

Keep up the great vids...

[@voxpathfinder15r]

This channel cracks the living shit out of me, keep up the good work!

[@smstiao-tecnologia]

Wonderful! We will be waiting.

[@tonedriverss8629]

Good tech , good humored guy , always very well done vids , Terry . Yes , too many cobblers around .. hit them hard in the head , hopefully they will learn something here.

[@youcefbouheraoua6160]

Hello, I have noticed that ground lug is close to power transformer. It is best practice to have ground connection close to preamp side.

[@raffyzoo2130]

i am just really glad that you are not my dentist-the way ya poke around in there!

[@jwl9286]

Another fantastic job. sometimes power supply current has to be emphasised. I love the way you pointed out how the 6v6 was the proper Match to the 5y3. Do you think a 5u4 would be okay with the 6v6?

[@Tomcatime]

I would really like to see you work on a Guild Thunderbird. Cause I have one and need help with it. I got my Gibson atlas working by watching your videos so. Thanks and keep it up

[@matthewf1979]

The reflected impedance with the EL34 on the yellow/black connection with an 8 ohm speaker would be 4.4k. Close enough to 3.6k on that universal tranny.

[@allanjohnston8049]

I would like to know more of thst really cool D lab output tester/power instrument

[@islanderwinder]

Great Video

[@DeadKoby]

I know that dude who built this did a rough looking job. My first amp was rough too. My second was better, and my third/forth were beauties and worked great the first time. Sometimes we have to learn the hard way.

[@d-labelectronics]

Roger that man. I agree. It took me many years to get to this point, and I still learn new things every repair or build. TD

[@jteichma]

Hi Terry, great video as always. Why does switching in the caps in the tone switch increase the amplitude of the signal, I thought caps worked more like filters on AC. Is it the amount of DC they let through to the plate?

[@smstiao-tecnologia]

Dear Tery, how are you? Very good work on this amplifier, bad contact is always a big problem when it comes to transistor sound equipment or using our beloved valves. Once again Congratulations on your work that has helped us a lot.

[@d-labelectronics]

Thank you my friend. More to come soon. TD

[@bluesman5049]

Respect. Which values should have, these three large electrolytic capacitors. What is their role in the amplifier, and whether they affect the clean tone of the amplifier.Do they have to have strictly defined values or have deviations? I mean this kind of amplifier with this scheme. In general, I am interested in which part of the amplifier is responsible for the clean tone. The lamps in my amplifier are EL84, Ecc81, EZ80. Thank you.

[@giulioluzzardi7632]

That was interesting, was it made with an EL34 or did some-one just stick one in in place of a 6v6? I would really like to see a video by you showing the various glows and colours different valves make when good or bad. Thanks.

[@reportingfromthebunker]

Hi D-lab. I have a Juketone (UK) 5F1 Clone. It has the Cliff style input jacks the same as above. I'd like to replace them with the switchcraft shorting plugs. I was warned about creating ground loops as the cliff type is insulated from the chassis. How do I determin if its okay to use the switchcraft type. As a sidenote I replaced the hardwired speaker leads with a 1/4" switchcraft mono jack so I could attach other speaker cabinets. There was no hum introduced by doing this. Thanks For Any Help. Nikki.

[@Immandil]

It always looks so easy, but it takes years of practice to simply poke stuff around, enlist exactly what to do and do it. Thanks for the video! Out of sheer curiosity, have you ever tried connecting tube amp output to input and starting an amp? If yes, what did explode first?

[@edwhite7475]

what brand of scope is that? i like the screen....easy to see

[@gri7]

Is there Way to test if a output Transformer is shot? My output signal is lost no hum. Replaced output tubes

[@jameswallace5967]

Was wòndering about having a separate ground for the power section and another for the preamp section?

[@thomasdoyle4485]

Im wondering what the 330pf capacitor does between the grid and cathode on the tube socket of the 6V6??? not all the schematics show it... was this added in later amps for some reason?

[@michel333100]

But Terry these particular 6V6's by JJ tubes can handle 500 volts on the plates, but is there a change in impedance with using this tube. Bob at Eurotubes in Oregon told me a few years ago that I could pop a quartet in my Mesa Tremoverb amp and that amp is somewhere around 460 volts on the plates. These JJ'S are not like typical 6V6's. they can definitely take the plate voltage on the Marshall JTM 45 at 416 volts on the plates. but like I was concerned about the impedance. presently I have these in with a GZ34 rectifier. but I have my cab at 16 ohms. I heard on the net that you should run the 16 ohm cab into the 8ohm output of the amp because of impedance mismatch. I need your advice on this. thanks Terry my amp seems to run just fine , but is it safe?

[@JohnvL]

Thanks

[@HarpinJScott]

Great videos Terry! One question: when checking the audio generator with the scope for proper millvolts and frequency, do I need to use a 50 ohm resistor on the scope side? I ask because I hooked my signal generator to my scope and the scope went haywire! I hope that makes sense...

[@d-labelectronics]

Hello, I use a 8 ohm dummy load resistor, parallel the scope across it. Make sure your scopes AC plug is ground isolated (no ground lug), and make sure to get the scopes probe polarity correct or it can short out the speaker output. TD

[@HarpinJScott]

Thanks for the response! I was wondering about the input. You demonstrated it in another video, but it wasn't quite clear. Thanks so much Terry! I've learned so much from this channel!

[@RexLancaster]

Thanks for all the very informative and at times entertaining videos. I am currently trying to reduce excessive hiss from my Selmer T&B Mk3, it also has the same pin 1 to ground tab (joined to pin 2) and plastic jack sockets with 4 solder lugs, the rear ones are linked and also go to pin 1 & ground. Will it be ok to keep those or would I benefit from a change to the switchcraft sockets?

[@d-labelectronics]

Go with the Switchcrafts if they will install OK. You will be happy you did.

[@RexLancaster]

Shall I leave pin 1 attached to the chassis ground?

[@d-labelectronics]

If its running a 6V6, that pin is not used

[@RexLancaster]

It runs 2 x EL34's. Pins 1 & 8 are connected (not 1&2 as I said above) they have no wire connection apart from the one to the jack sockets. I read pin 1 would normally be suppressor grid connected to pin 8 cathode. Maybe Selmer did things a little differently.. music-electronics-forum.com/attachments/7195d1260324513-mkiii.gif

[@LincolnFStern]

The only valid reason for not installing switchcraft jacks is that you can't get them wherever you are. If you work on amps or guitars you should have a drawer full of them. :)

[@jrcenina85]

Hello, thanks for all the posts! Did you ever zero-in on what was causing the pulsating sine wave around the 7:27 mark?

[@d-labelectronics]

Nope, the issue went away after installing the 6V6. It could have been due to pin 1 of the EL34 being tied to ground. That is a grid connection for that tube. If there was any 60hz noise floating on the chassis, it could have induced into the tube? Just a guess.

[@jrcenina85]

D-lab Electronics thanks for the quick response!

[@TheDudesdad2000]

Terry, Appreciate this video, since I am building one at the moment. I have an unrelated question regarding standby switches on tube amps. First, are they primarily only used on diode rectified amps? Second, does eliminating the standby switch in a tube amp that normally uses one affect tube life or performance overall? Thanks again for all you do for tube lovers. Cheers.

[@Immandil]

As far as a DIY person can tell, standby circuitry is installed to ensure proper tube heating before attaching high voltage to their anodes. On specifics, I would count on Terry here. To answer your diode question at least partially - Mesa Boogie Dual Rectifier guitar amp has ability to rectify high voltage either through silicon diodes or 5U4 tubes. Standby switch is used there with no regard to the rectifier used. I hope this helps a bit :)

[@silasfatchett5693]

All you need to know about the pros and cons of standby switches at valvewizard.co.uk. If you're building an amp you should check it out.

[@tubetone74]

Terry, do you use crazy glue on the "nail down" of the caps?

[@d-labelectronics]

Nope, I use E6000, clear adhesive

[@drdave337]

Just curious- Where did you get that metal shelving from? It adds a nice touch.

[@d-labelectronics]

It was military surplus. I have transported them with me across the USA!

[@jjcreel9158]

No time for wine on this amp! :)

[@elwrongo]

Great video yet again Terry, I'm hooked. Although I must admit I was shocked at the sudden violence meted out to The Cobbler. Perhaps an audience rating is in order?

[@MrBeblis]

Can everything be grounded to one spot or is it better to ground the power section separate from preamp? Thank you

[@michaelsorenson3887]

Keep all grounds short. The shortest path is generally the best, but look up star ground. You dont need them all on one solder blob, but soldering them to the chassis serves the same purpose. Ground is ground is ground. Just dont make a ground loop where one point would be a higher potential than the other. Just research everything on grounding methods and connect the dots for yourself with what makes sense to you.

[@michel333100]

Hi Terry, I have a question for you. Can JJ 6v6's be used in a Marshall JTM 45 bluesbreaker amp? you mentioned that these 6v6's have a different impedance. can the JJ'S be substituted for KT66'S in an amp like this? would you have to change the rectifier GZ34 for a 5R4 or 5Y3?

[@d-labelectronics]

Hello, the 6V6 tube cannot handle the high voltage that a Marshall runs. They would quickly ark and fail. Not recommended

[@daveogarf]

YAYYY, "The Cobbler"! What a corny character - and all too common. My guess is that his English cousin is "The Bodger". I used to have Resistoroids. Changed my diet and they went away.

[@ZillaYT]

Is this based on the original blackface Fender Champ?

[@crgwfrench]

10:46 to 10:57 why the left finger on the chassis? Scary 11 seconds!

[@jamiboothe]

I have never heard of a single ended EL34 amp. I am fine with being ignorant in amplifier designs, I think they are fantastic power tubes, but to put one in place of a 6v6 is weird.

[@jackcraven4591]

terry, sorry to be pedantic, but 5f2 is princeton. champ is 5f1. good video!

[@matthewf1979]

Jack Craven i was just about to say the same thing. The amps are very similar though.

[@d-labelectronics]

Oops, mis-spoke, good catch

[@sfmag1]

Hey hey hey you need froggie from the ghoul!

[@RobertKohut]

Nice!! That Cobbler is so corny!!...LOL

[@kendavis8046]

What, no sine? :-)

[@kendavis8046]

oops - wine

[@d-labelectronics]

Shot the video at noon Sunday. Wine breaks out after 4:30pm, D-lab rules.

[@silasfatchett5693]

It's always after 4:30 pm somewhere!

[@stratslinger4492]

The Cobbler-lmao!!

[@billdyke9745]

Boo-hoo-tique... Be nice to hear some guitar through these things. Compared to this stuff, the old 3 chord trick is stupidly simple. If it was hard they wouldn't get guitar players to do it...

[@kevingray707]

Prefer just showing the improvements. Could do without all the sarcastic attitude. The Corn man doesn’t add anything to the video.