How to fix smoking Fender 5F1 Tube Champ guitar amp kit repair D-Lab 

A tip for kit builders, as taught to me by my high school electronics teacher: Make a copy of the schematic you are building, and use a highlighter pen to mark off each component and conductor as you install them.

From Leo: Nice quick fix. I have repaired maybe 1/2 dozen recent production Fender blues juniors that have flame proof resistors on the output tubes that are undersized. All the old ones had bigger resistors. Being flame proof, they do not discolor, they just go open. It is like the purchasing managers are over riding the engineering department. Extra repair cost because someone saved 2 pennies on the resistors.

I watch every video..This can't be true, what a coincidence. I just bought a bad smelling and humming Champ yesterday for (I'm sorry to tell) $15, on a flee market with exact the same issue, and now Terry placed a vid. This helps me again Many Thanks Terry! 👍🏼

Just a weird thought. Did the client ever say that the amp was working before? That wire could be dangling under the board. I had that happen once where something got a little over-soldered on the top, and the wire under the board fell out. You could have 400 volts dangling around in there somewhere haha.

Very interesting episode.... I'd love to build an amp kit one day despite having no electronics experience what-so-ever. I have a Fender Princeton Reverb reissue - bought it new a few years ago... had not played it for even an hour before a power tube went out on it... the amp tech I took it to for repair replaced the Fender original tubes (both of them) with JJs... said it was the 'mid-range' option. Put a lot of hours of them - no problems so far.

Just put in the wire that I missed. Left in that 470ohm resistor and the amp sounds great. What puzzles me is the fact that there is that big orange drop cap that feeds the 12ax7 pin 3, where I have a 1.5k resistor. Well, my amp works fine, thanks to you and this video Terry.

Yes the biasing resistor should be in the 5 watt range, but 470 ohms is definitely NOT too low. It’s a standard value for a 6V6 tube. If you put in a 1K you’re biasing the amp way too cold.

Great video. Can't believe you pulled out an Angel CD! One of my faves back in high school. Converted (with help) a late 50's Voice of Music reel-to-reel tape recorder amp to a 5F1.

Wow i just saw whats left of ANGEL last year .barry the drummer and frank the singer are the original members. You have great taste in music mr D Lab.

I would have lifted that turret board to see if there was a wire under there that had come loose before adding a strap wire over the top. A loose wire connected to high voltage on one end could move around and touch other circuit components and burn them up too.

I was like I just subscribed what did I do? Then he said JJ Tubes. Cheers!

all the jj tube i have used have been faulty 6l6 6v6 6bq5 5y5 12axt 12au7 12at7

I agree about JJ...I have had some bad ones out of the box.

Great video! I missed that jumper wire on my first Marshall 18 watt build. The next build, I had one wire too many!

i saw Angel in concert. great show

I remember seeing Angel perform in Albany back around 1978. They played at the historic old Palace Theater.

Love your videos Terry! I'm wondering, how do you stock and organize your shop? You always seem to have many components and tubes readily on hand... I'd love to see a walk-through video of your shop to see how you keep things organized and what you find useful to keep in stock! ...my hobby has turned into more constant work over the last few years, but I feel like I'm still spending too much time looking for things, despite having reorganized a few times.

Quick and dirty repair.... jus the way we like them. Well done Terry !

I built a 5F3+ Tweed kit from Tube Depot last month. I think (hope) I upgraded the tubes for JJ. I looked at Tube Depot's 5F1 schematics and they call for a 470Ω 1W resistor where that 1/2W 470Ω resistor was in this one. But... after running the numbers in a bias calculator, the 470Ω resistor would make for a bias that's a bit hot (as you noted).

That’s a real shame about the JJ 5Y3’s. They’re the only ones made today as a real 5Y3, all the rest are relabeled 5AR4/GZ34’s

Hi Terry -- please inform the builder to wire the hot from the wall to the TIP of the fuseholder -- and what are those wirenuts doing in there ? Peace

US East Coast heavy metal band from the late 1970s to early 1980s. If I could but understand half of what you say I'd buy that CD even though I didn't like any of their music.

A common theme of of the home built amps is over looked or outright botched wiring. Even on a simple amp to a neophytes eye it looks like spaghetti. Very interesting is stewmac selling what looks to be an expanding line of mojotone kits which is great! Unique about stewmac is a detailed pdf step by step construction manual downloadable for free! My only confusion is they state that resisters orientation isn,t important and the orange drop caps orientation isn,t an ussue!????don,t they have polarity???? Another question mark is the use of predominately yellow wires. I thought the SOP is black =ground, yellow -signal, red- high voltage and green heaters. But still very usefull and informative. Maybe you could have a look and share your thoughts!

When Jan Jurco bought the Tesla factory, we all had hope but Jan's designs have had a bad habit of burning out on the power and rectifier tubes. His preamp tubes are noisy and very inconsistent. Yes, his tubes can be powerful but when they fail so often, even when you find a good one or set, you are making a huge gamble. I personally do not sell or install JJ tubes in any of my repairs. As a matter of tone and longevity, I only use vintage tubes in my vintage repairs! Of course, then I won't have that customer back for 5-10 yrs if their only recording with the amp. Maybe more than a year if their playing steady gigs for power tube replacement (depending on volume).

Oscillatin’ Television! Excellent!

No way , Angel? Lol saw them in Cleveland in late 70’s.

390v B+ seems a little hot for the 5F1. I'm used to seeing 360v and below, and probably why he needed a 1k resistor to tame the cathode bias.

excellent video

I had to do the same thing to my home built 5F2A amp and installed a 1K/3w.

Thanks Terry. Just built the same amp. Guess what? No sound. No smoke yet. Still has the new amp smell to it. I forgot that wire. Maybe that's why I have no power to my 12ax7. I think I will replace that 470ohm resistor though. Got two questions for you. On the end of my eyelet board and the layout, there is a 1.5k 1/2 watt "resistor" that goes to pin 3 of the 12ax7. Do you recall the value of that orange drop "cap"? I'm a newbe at this, but so far having a good experience. But when can you use a "cap" to replace a "resistor"? BTW that guys build looks so much better than mine. Good vid.

Thanks Terry!

Angel, the Anti-Kiss. Still have my vinyl.

I just threw out a 5y3 & 6v6 by jj. I didnt have them that long either.

Buy from a reputable dealer. All the current tube brands are shipping duds... The good resellers will burn in and test the tubes, the consumer never sees or knows about the duds. I use lots of JJ tubes purchased from a USA based dealer in Oregon. They burn in and grade every tube.. over many years and hundreds of tubes, never a dud...

Hi terry! Nice video! I have a question. The pot, it's alpha? I have noticed that it's turns on at 2 and just reach to 11 (it's like the rotation of the pot doesn't match with all the chassis on sale). Thanks for your time. Regards!

The original 5F1 schematic shows this as a 470 ohm cathode resistor for the 6V6. I understand increasing the power rating above 1/2W - most kits I've seen are coming with a 3-5W 470ohm... But how did you determine that 1kohm is the right resistor?

I tell everyone to watch your channel and subscribe. You deserve more subscribers, always great content and a good guy too. Thanks buddy, keep up the good work.

Hi Terry, love your videos. I always take a photo of underboard links when I build, that is handy in circumstances like this. Also, won't such a change of bias resistor make the valve run cooler enough to change the sound?

The kit I have, but have not yet completed came with a 1 watt 470 ohm, but I'll probably get a different one after watching this. I looked at the schematic for the 5F1 and if I'm reading it correctly, it does call for a 470 ohm resistor... Would you say that it's a design flaw?

Is the cool bias the reason your wave looked so clean even when you cranked up the volume. I thought the champ would clip a little a full volume to get that bluesy sound.

Are you finding that these kits are not having the right resistors and in this case a Jumper? or did the assembler just miss them?

Hello Terry, Thanks for this video! I did the 1kΩ 5w swap on a 5F1 b/c of high B+ voltage w/470Ω. After rolling a few tube sets, I ended up with an EH 6v6 and Sovtek 5AR4 which measured out to be about 11 watts at idle and 93ish % dissipation with a Classic Tone15w OT which I think can take up to 70mA. I Would like to try a lower value resistor although I'm not sure how far over 100% dissipation is "safe" for a 6v6. In one of your builds, I saw that you biased a 6L6 to 40 mA. Is 40 mA a magic number for 6V6 tubes as well? Sounds pretty good as-is but I'm just curious how far I can go with this. Thanks for all of your efforts..

ho it s long time i didn t see a D-lab video ! i was attract by smoke !

Terry, what is your opinion on "starved cathode/anode" pre amp circuits? Are they a waste of time or a quick and easy way to boost a singal?

Nice!! Great video.... :-)

Hello and good afternoon I love your videos they are very intuitive. Quick question for you I have 2 Jensen F12 speakers field coil one is a F12 NC and one is a F12 n s the NS is 700 Ohms on the field coil and the NC is 1000 Ohms on the field coil both are 6.5 Ohms on the voice coil do you think I could use them as a pair or would they sound difference with a 300 ohm difference thank you

Hope Fender didn't supply that resistor in the kit, but OTOH I would expect a kit to contain all resistors. Very strange.

I got out of the tube repair game a couple of years ago, JJ tubes made me quit, they suck big time! I had many preamp and power amp tubes, blow up, puncture, they did not fit the sockets, pins where too small, just a world of problems! Tubes suck now a days unfortunately, trying to make a living repairing amps, forget it!!!

Hi Terry, I heard a youtuber comment yesterday that there are only 3 plants worldwide that manufacture "TUBES"... Could you maybe sometime comment on that?? Russia, Slovakia(??) and China... The context was "branded" and "unbranded" tubes... The Q is related to JJ tubes.... made in China?? btw... Great repair, love watching your logic!

Do not adjust your oscillator, we re in control.lol

1/2 watt?? oh no...

Where’s our video? LOL

Bet ya didnt know Stan Lee could fix amps did ya. Yup