Fender Champ tube practice guitar amp repair tips How to by D-lab 

Love your videos Terry. They hold a very special place in my heart. In 1976 I bought a used Fender Deluxe Reverb (black) for $150 bucks from my grocery store job that paid $3.00 an hour. It was not in very good shape, but man, I learned quickly from it, learned to solder, and even started building radios after that. 25 years after I sold the Deluxe Reverb , I bumped into the musician that had purchased it from me. He said that it was still going strong. Keep up the good work, and your great teaching!

Thank you for your help. I repair amplifiers here in Hawaii on the Big Island and there is only one other person that does repairs. So you're videos are appreciated. Thank you. Aloha, Darrell

Nice video, Terry! You're exactly right on the whole "one problem leads to another" when it comes to tube amps. What was supposed to be a simple fix becomes not so simple. Things get out of hand fast.

One of the best amp diagnostic videos I have ever seen...Cheers to you D-Lab!!!

Always looking for a easy fix sometimes leads to a headache!Your right a little help from Bob always leads to a better end.Great videos,you remind of my high school Electronics Teacher ,always showing you why,how,and the right way to do it.Thanks

You are my hero! Please, keep making these videos! I wish there were more people like you in the world who take their time and talent and show the rest of us the tips and tricks that years of experience have over anything found in a book. Thank you!

thank you!!!! i just bought one of these bad boys and i had so many probs. fixed it up for no cost and it plays like a little dream

Fun video with a great variety of issues that can come from such a simple circuit. Thank you sir, love the final Cabernet touch ;)

Like all of your episodes Terry,sometimes I make a rerun of some old ones like this,keep up the good work,regards Colin.

Amazing content!!! Thank you!! You are helping me start my journey! Looking forward to learning much more from you. Thank you.

Good stuff !! I'm getting back into tube amp repair, all these videos help a lot.

fantastic guitar test at the end we really get to hear the amp real world!!! thank you!~

Sounds like the adventures I've had in a few vintage amps.... I did a Blackface Bassman 50.... and when one thing was fixed, another one cropped up. I've had it working happily in service for a half a month now. I seriously think I finally GOT IT.

Enjoying your videos Terry. I've refurbished 1/2 a dozen or so Champs & Vibros and they have all had that 2mfd 25v cap which is also shown on all the schematics beginning with the AA764 Blackface. I've always upgraded it to 50 volts as well. The reason for the high current on the 6V6 is if you check, you'll find that the late 70's and on have PT's with a B+ that's 50-60 volts Over the original specs. With typical home line voltages running closer to 125v than 117v doesn't help either!

These are perhaps the very best sounding amps that Fender ever made ... BIG statement, I know, what with the likes of the tweed Deluxe and the tweed Bassman and the Vibroberb and Super Reverb and Vibrolux! But this Class A or single-ended design, just sounds incredible to my ears, after 60 years of guitar playing ...

Very nicely done; I have run into similar situations where you have a number of cascade problems that must be resolved one by one, patients pays off.

D Lab to D Future😎 Pls keep posing more fix it helps me and motivates me to learn how to fix tube amps...more power wisdom n knowledge to U Sir!!

At the end of the day, the amp is fixed, and you repaired it. Great Video, thank you.

I'm an engineer (BSEE Cal Poly SLO & MSEE SCU) - but choose to work from home. I have a small lab and bought my own software for jobs. I can relate to two things you've mentioned in this video 1) I work three times as much for have the cash 2) it isn't unusual for me to have a glass of nice red wine - I like CA Pinot & Spanish Tempranillo - yummie Just noticed a Ham call sign in one of your videos - I haven't been on the air in so long that I didn't even notice the got rid of Morse code requirements - I was a Tech Plus back in the day - KD6NCR (my S.O. is KK6ONC) I worked at Vandenberg AFB in Lompoc. I grew up in the Santa Maria, CA area - known as the Central Coast.

LOL! "El Junkaramus"! TOO GOOD! Please keep 'em comin', Terry.

The old "house of cards" amp repair. Gotta love it. Terry, please do a video of a customer who wants his amp problem diagnosed over the phone for free without you ever taking a look at it. Have a great week!

Great video. I found it very informative! Even with such a simple circuit, so many things can be wonky contributing to performance issues.

Thanks for the video, Terry! The ending cracked me up, as I was finishing a glass of red wine as the video ended :)

Love this old video...seems much like my amp fix woes... Never ending battle with seemingly simple things...lol

Great Job analyzing the Champ Terry!

Genius!!! Loved your video... I have an old fender video champ... 1970 Still holding up well, but looks like it could ready to go at any point... hope there’s someone around as good as you to look it over!!

You make very nice videos Terry with various tube equipment. I recently repaired/restored a 1956 Fender Tweed Deluxe replacing the audio output transformer, caps, tubes and repairing the voice coil in the Jensen Speaker. I used "Goop" to reattach the cone and it now sounds great. 73.....

Terry, enjoyed the video. We REALLY need a D-Lab-type shop in my town. Cheers.

Very informative an educational as always, thanks Terry. Cheers, amigo! :-)

Great video! Always helpful! I have a question, I bought a standby switch for my blues jr and I don't see any videos on how to install, can you help?

Celebrating with Communion wine. Gotta love this guy. 😁

Enjoy the Vino . Great videos TXS. From Ireland hello

Great video! You're so right about one thing cascading into more problems on these old valve amps. But what is a whole lot worse is working on old classic US car. Something that sort of surprised me when working on my '65 Olds Cutlass was that behind the dash is a large (2ft) circuit board that has a big multiplug at one end. The dash instrument lamps etc just plug straight into the circuit board.Any idea how long circuit boards have been used by manufacturers?

"So you wonder why things get so expensive in the repair shop?" Love it! Cause I work in a repair shop :)

glad to see I'm not the only tech that can fix and not play

Really great video appreciate this so much, thanks, D

Nice video... doing that bias was really helpful also.

Good job Terry, on the Vino.

Thank you Terry...great vid...you have to be relentless with electronics...cheers

Just the reason I got out of repairing pianos. "It was just a sticky key!" HA! JUST?!

I love champs great video

Hello Terry, have a question, when reading tube data sheets say RCA they give you a "series column and a parallel column. Which column do I read when working on amplifiers? Thanks

Just finished repairing an earl 60's Gibson amp that was a nightmare. Just like this, one problem after another. Finally one problem was really throwing me off - I thought the owner was gonna kill me cuz I just couldn't figure out what was wrong. I put it all back in the case and tried one more time, and whadaya know? It starts working beautifully! The tone controls were dangling about 5" from the power tube sockets instead of being a bit above like when installed - it had me running in circles... There were in addition almost all resistors and caps over 20% out of spec and leaky... I'm a part time fixer, but I'm henceforth gonna be choosy about my repair projects... Great video, and thanks for sharing!

Great video.. I own a '73 Champ myself. What is the difference between input 1 and 2. Is there any...?

Terry-I got my first amp in 1959 or 1960, it was a Fender Tweed, and I believe it was either a Champ or a Harvard. I know it only had 1 speaker, and I think it was oval. It was pretty small, and of course basic. I'm thinking of building one and trying to figure out which one I had, and/or which one is the better choice if there's no way to tell now which model I had. Do you have any thoughts to help me on this. Thanks.

Terry, any idea what the Fender factory is painting the bias pots with to lock them down? My Super Champ had a dab of red (paint?) holding the bias pot setting from changing. When I retubed the amp the red stuff broke loose easy enough when I rebiased the amp. I'm guessing automotive touch-up paint or fingernail polish. What do you recommend using to hold the bias setting in place?

It's amazing how one issue leads to another in a chain. This has happened to me many times...a customer would bring in an amplifier and describes the symptoms as being just a noisy tube. In the mean time, new set of tubes, jacks, and 5 filter capacitors later the amp is finally working...Oh, I'm sorry, I forgot the bias supply filter cap (which makes 6) :) Then the after everything is working great, the customer cry's the blues instead of playing them. Well, for 75 bucks an hour they can't go wrong...but try telling them that LOL Great videos!!! Keep 'em coming. Frank Ferraro--Audio Craft Electronics

Hi Terry ,, love your videos,, Did you check the plate and filament voltage on that amp.. A 1K bias reisistor seems high for a 6v6gt class A amp. I checked the schematic and the plate voltage should be ~ 350VDC. But even at that voltage the bias should be very hot with a 470r bias resistor as the plate and screen are only separated with a 1K resistor. The Fender tweed champ should have around 330-340V on the plates but the screen sits lower as you have a 10k resistor between them,, so the bias with a ~500r resistor is more reasonable.. To my understanding,, high plate and screen voltage with a high bias resistor value is not the greatest solution for a class A amp...The RCA 6v6gt sheet says ~ 50mA total cathode current at 250V plate/screen with a 5K reflected load, With 315V plate and 230V screen the total cathode current should be around 36mA with a 8.5K reflected load.

Another great video Terry! Don't have to give an excuse for the wine drinking cause I would too if they let me at work! Oh and don't listen to the haters they are all just jealous that they don't have your talent!

Hi Doctor!! excuse me I have a Fender Twin Reverb 65 made in 1990 but I have a problem with my amp. the reverb effect does not work at all and I don't really know what I get to do? do you think is only clean inside of the Reverb Tank maybe have to much dust inside or That is wrong if I try to do that? and what kind cleaner spray I can use for the amps and guitars controls? thank you so much!

Love this guy!

Nice interesting video Ted, if you don't mind me asking, for the scope view, where would one hook up the probes, at the speaker + - or before the OT?

I think you'll find that most vintage amps run at a voltage that is higher than spec due to the 9% or better increase in wall voltage ( from 110v to 120v or even more) and will throw cap voltage rating out of spec , that being said what harm is there in having a higher voltage rating for a bypass cap , if the uf rating is the same ?

LOVE YOUR VIDEOS MAN ;)

Recently re-capped a Vibro Champ. It also had a 2uf @ 50v bypass CAP. Mine was located on the first half of the V1. Looked original to the amp. Something tells me this CAP was an intentional install. My amp sounds great after re-capping with 25uf 25v CAPS. Wondering how many other Champs are carrying a 2 uf @ 50v? Thanks for the upload.

Nice video, good info. You're a funny guy

I know this is an old vid, but learning cure is always present..Top fix and info..Ed..u.k..😀

Top drawer!!! Thank you!

Which type of signal generator did you use in this video? It looked like the size of an Ohm meter.

That sure is a clean champ

Terry, all you're stuff is great! I recently replaced a 470ohm bias resistor with a 1k on my champ project as you suggested. It will take you about one day to learn to tune and play three chords on your guitar. Just sayin'...

Pretty nice video Terry! Just made me to subscribe! Can you make a video about to poking inside the amp with an oscilloscope to find bad components? Greetings from Hungary!

Terry, if that bias resistor had not gone up in value and was still 470 which is the correct stock resistor, the idle would be even higher about 57.4 mA. Is this because other component values have strayed over time to cause the voltage drop at that point to have strayed higher over time? Just trying to figure this stuff out, thanks for the great tutorials!

I use a 6mm (.253 cal) bore brush used for cleaning rifle barrels, with a tele volume knob glued on for a handle to clean jack socket sleeves. They tarnish with weather change and fuck up the earth to shield connection. Cost less than $10 to make...

HELP?!. Sir, I purchased a new Fender Rumble 25 Bass amp, 3 weeks later I plug in, turn on ....and no sound? Amp makes power up sound at speaker be when pwr switch is depressed. No loose plugs, knobs, and never dropped. Plz help.

what was the fix to the triangulated sine wave form?

I understanding wy you drinking wine after repair! It's a victory liqued! Santé

Cheers man, you've earned :)

Great video. Thank you

Hey Terry, do you have any videos on troubleshooting pots not working when it's not the pot itself that's faulty? On a fender handwired amp

You're so right about the underlying problems! I cleaned my 12AX7 pins and sockets and thought wow, it's all fixed! Not. After watching your videos, I found some caps that looked pregnant, one had a piece of rubber about to blow out the end, and another was leaking. I learned there's always more to it than you think! Thanks for all your help!

Terry you crack me up sometimes! I don't know where you live, but I wish I lived by you as you would be fun to hang out with. I recently finished my 1st amp build, a fender champ/early Princeton/Uncle Doug clone. I think it came out rather well. I had initially purchased an old broken Hammond L100 to convert to a guitar amp, but soon realized I didn't know enough about amplifier circuits to do it. I started watching various people (you are one) on RU-vid, and well, I think I can do it now. That will be my 1st PP amp. I am making a video of the champ and will send you a link. Let me know what you think. Thanks for making your video's, Tom

Thanks for the video. The best advice was the Robert Mondavi assist at the end. I've got one amp that been on my bench for a couple of months that's a Jose Cuervo type. Finally just ordered the power amp from Peavey. Dead short in the DC section. Replaced all the transistors, caps, and resistors. It's a good thing I've got a day job to pay bills. My real question is: What type of signal generator are you using? Does it have square, sine and notch wave?

How much does a tube-checking-device cost? Because Im wondering if its worth installing it in an amp.

Great video,s Terry. Better than NETFLIX!! 😁 Can you show us how to get rid of hum in Fender Vibrochamp amps?

Thank you for this. Are the speakers connected as well ( in parallel ) as the scope?

I like your style! boom!

What spray product do you use on the pots, Terry?

I have run across plate load resistors making noise several times. Doing your test, the static on the trace makes finding those easy. They make an intermittent static once the amp warms up. There is no other way to test them other than swapping them out.

Learn to strum a simple 'C' & 'G' cord...as always great job!

Doc Terry can we put a Clutch Capacitor to boost d amp over drive much better?!?😅 Hey Doc i watch ur video at work everyday here in our car dealership ! more power Doc...

for a diy 6l6 single guitar amp , what do you recommend for plate voltage and cathode resistor and bias current .

You can't get too much more simple than a single ended Fender Champ amp. Some of them do have some maddening multiple issues though, especially when someone tries to hot-mod it, and gets it wrong. I have even seen factory mistakes in the pre-1985 stuff. .003uF caps in place of .03. That tremolo circuit never worked right for over 50 years, with that cap in there. Just for fun, take me through an Engl Fireball. I have been through one, and I really just want to see someone else suffer through Engl's inaccurate schematics. Enjoy the mislabeled components, unlabeled components, and various relay circuit lines that go to nowhere, have no IDs and just leave you guessing. Best advice, pretend there is no schematic for it, and work from theory of operation. I don't use an Apmlitex anymore. Mine blew up a Telefunken YL1350 Engineering sample prototype. I happily sold it and upgraded some vintage tube testers & a couple curve tracers with regulated PSUs, and test sockets for use with Kelvin lead DVMs. Now I am working on a PIC based tester, and an Arduino based tester. One of the best investment I made was a good quality, but dated LCR bridge. What a versatile time saver those are. I even bought a cheap Asian spare. I have a 371B curve tracer, and am working on high power RF & ham radio gear too. Anyone with the big power linear amps usually has more money than musicians in these parts. Same with most people who own Marantz Model 7,8 and or 9, Conrad Johnson, Mc Intosh, etc. That work kind of picks up some of the financial slack for the guitar amp work. Musicians here are very underpaid too. The good ones spend their summers in Europe and make 20-100X more for a show.

Hi, i really like your videos. thx a lot! 1 question: what resistor value did you installed to get the bias down to 34ma? the original was 520 ohm, but i couldnt see the value of the replacement resistor. thx....Stefan from Belgium.

Spot on

My 1970 fender champ also has a 2uf capacitor in same place. I replaced the 25uf caps but can I swap the 2uf for a 25uf?

I had a Bronco try to kick my butt one time. After fixing a Super Reverb, Carvin, and a Marshall, one of these little simpletons drove me crazy! I kept finding little problems, but the one that was causing the issue. It ended up being the ground to the chassis of the 6V6 cathode resistor. It looked good on a quick visual, but was loose. A reflow fixed it.

Enjoyed the video, Lighting is a little dim. I sure hope you charged more than $50!! LOL I have 2 small amps and a pedal I need repaired but afraid to get the bill!!

You are awesome! Too bad I have a Fender Acoustasonic (Non-tube) having intermittent hum issues. A tap on the amp sometimes makes it quiet. It has been a great acoustic amp. Any Ideas? Randy

I never trust lock washers for grounding. Usually the jacks have a ground tab and bridging these with wires to ground is a sure fix.

One of these days I'm going to drive up there to Michoacan and teach you a guitar chord; in the meantime, you think about which one you want to learn...

I would like to know how to figure out the year on the champ I have the same champ amp Ab764 but no ser number Schematic has I-FD on it Don't know what that is CBS musical instruments Last numbers on output former is xxx-3-28

What kind of mini tone generator is that? Looks like the size of your multimeter. I like that thing.

awesome video..d-lab. My champ lights up fine..Its a new Fender Champ XD..but no sound comes out of it..can tell from this 7 word description what's wrong with it?

Wow! I always wandered what Ned Flanders does for a living! Great job :-)

Nice work, but that is not a lock washer, it is a toothed washer on the input jacks. FWIW, I also will have a glass of cabernet sometimes when I am working on an amp in the evening.

Thanks for the insight... and for sure.. you gotta have a celebration glass of wine.. I know I do )))

Kinda new to this..which pin on the 6V6 tube is the resistor hooked to??? Thanks..

Hi Terry. What value power resistor are you using for the dummy load, and how would you determine which value is needed?

Got 75' vibro champ with a high pitched squeal at 0-3 then again from 7-10 changed tubes (new) ,, any ideas... ???