How to fix Fender 5F1 Tube MojoTone Kit amplifier Simple repair Tips

Many of these kit build Fender 5F1 amps have came thru the doors of D-Lab lately. So I determined that this was a good time to launch a common problem video to assist you with problems that may arise. Fender is the fore founder of tube amps. I plan to support their creations as long as I am capable. Remember guys, this is just a part time gig for me, a hobby. Someday maybe a full time profession. Depends on how well I have planned my retirement! Thanks for watching, I will keep the ball rolling.

[@edwardebel1847]

I feel like I'm back at university...I'm building a Deluxe kit and I'm absolutely positive it would either not work at all or have numerous issues if not for these videos. Latest "lesson" for me is where to land the hot mains wire... I almost feel like I should watch every possible D-Lab video before finishing my kit. THANKS!

[@voxpathfinder15r]

It would be super cool if you could group all the 5f1 related videos into one category so we could easily binge watch all of them

[@ctcards2636]

I agree.

[@brucew9533]

Yes please. And more of them maybe modifying them for different tones.

[@johnstokes2246]

I have been playing with electronics for about 70 years and every time I watch one of your videos I learn something new. Thanks, John.

[@allanjohnston8049]

You have an awesome way of walkng someone through an amp repair I watch these videos sometimes 2 or 3 times watching you work on them It is good I dont live next door, lol, because I would be at your shop daily!!!!

[@DeathCapAmplification]

Great video and tips Terry! Keep em coming! I really enjoy your explanations of WHY you suggest doing things certain ways and how it makes the amps better. Really helpful tips. Thank you!

[@Finom1]

Thank you for sharing your wisdom with us!!! You always make fantastic educational videos with attention to all safety issues!!!

[@Rodedog55]

Thanks for the Video of the 5F1 Champ upgrades. Great clear explanations and nice upgrades here. Kudo's to ya!

[@TheDesertRat31]

I'm loving the 5f1 videos and discussion. I have a boothill kit that has gotten delayed so I'm happy to find all these tips yo add to my notes for when I get time to start my build. I've always planned to go with a 10" speaker and I've also liked the separate power switch as well.

[@robertcalkjr.8325]

Thanks Terry! Nice lesson and thanks for the tips. I have no problem with vintage meters. If I could afford to, I would collect them.

[@wadehicks9270]

Really digging those old meters. The corse I took in electronics came with a Beckmann meter their super nice, great video 👌👌👌👌👌

[@GUNFREAK2000]

These little amps are incredible!! You’ve got me addicted to these things!! I’m stripping old junk radio cabinets and gaining a huge chassis graveyard!! Thanks for all of this knowledge in easy to consume video format! :-)

[@Yupppi]

So many tips and lessons in this single short video that I haven't heard elsewhere. Thanks a bunch. Looking to build a nice little champ, although "v2", by this shop that's improved the old build a bit to meet modern standards (including things like power toggle, but also quality of life like multiple speaker load outputs and tone control :) ), these tips will definitely help judging my work, considering little mods and just safe practice in general.

[@kenhaywood3124]

I love your vids. The safety tips are spot on. Kudos from Ken in NC.

[@rockettcrawford890]

That was a great tip about moving the two input jacks to the outside to wire them before moving them back inside the chassis. I did a 5F1 build this last week and that tip really came in handy. Made it so much easier. I also appreciated the tip about wiring the hot to the tip of the fuse holder.

[@jonpardue]

Nice kit amplifier save and a ton solid of information. Interesting mention the old potentiometer/switch design having a solid metal back to block AF interference.

[@jp040759]

Great fuse tip. Never even thought about the hazardous scenario.

[@kendavis8046]

Thanks, Terry. I don't know if I will ever build one of these, but I am about to retire, so I will have the time. And I've got no problems with your meters!

[@fieldofweeds]

Thanks for all the great info! When I do my build, I’ll follow your suggestions.

[@ois-jy9kl]

I was finising my 5f1 project and I shaw that video a vew month's back .. I remembered the fuse trick descibed at 10:00... I looked for this video four about 3 hours and finally found it 😊

[@jameswallace5967]

Thank yoù for these wonderful vidoes. I replaced the 470 with a 750 ohm cathode bias resistor and was then able to get my 14 watts of plate dissipation. Thanks for the tip!

[@islanderwinder]

Thanks Terry , Great video , Nice tip on the fuse holder .

[@exceptions9263]

Also the switched pot. Does anyone make a pot like that with proper internal shielding?

[@garyp5522]

Great Video. I am getting ready to build a 5F1 and you have a lot of good information on this video. Thank You.

[@tedfrisk4730]

Job well done Sir, thanks for all info on rebuilding amps..

[@LarryDeSilva64]

Thanks for all the tips Terry. I have my old Beckman digital that still works great and use it on my videos as well.

[@jimcatanzaro7808]

Hi terry I have 20 chassis I made up from scrap and horded parts for the last 5 years I’m going to start building them this year I can’t wait your videos are great been watching for a long time

[@justsumguy2u]

Kit amps can be a ton of fun to assemble, but as you illustrated, not everyone is skilled at it. Your version looks (and works) infinitely better than when you got it, that's for sure!

[@audiotechlabs4650]

Terry, you could open a school to teach 'tronx when you retire! Great tutorial on what to do and what not to do. The 5F1 must be Leo's greatest model! Everyone likes it, me too! Thanxz

[@user-ig4wc1hi4d]

From your brother in Hawaii. Love your videos , and love you so much .

[@johnsimms3957]

Great video Terry!

[@neusprach]

Invaluable information. Thanks for sharing!

[@ctcards2636]

Thanks for that mid thing for making it like a Princeton. I added this to mine with a switch and now I can get 2 different voicing out of the 5f1. ;-) Love your videos, thanks for posting

[@Slugg-O]

Thanks for the tips on tweaking the tone. I'll try larger caps as suggested.

[@panther289]

Thank you for posting this video. I was going to start this kit this week. Now I have a shopping list to make the "improvements".

[@russellesimonetta3835]

Hey stewmac has downloadable instructions to get the amp built without problems. Could save you unnessisary mistakes. Infact i think stewmac kits are made by mojotone. Lots of yellow wires!!!!

[@panther289]

@@russellesimonetta3835 I saw the Stew Mac kits instructions pdf about a week or so back. It seems like a very comprehensive set of instructions. Was thinking of the stand alone reverb unit 6G15 as I just sold my reissue a few months ago. I agree with you about all the yellow wires. Could be the same.

[@russellesimonetta3835]

@@panther289 do the revibe from weber! It has fender trem and reverb. I think it,s the ultimate.

[@halbertking2683]

When it comes to repairing kit amps it's like "Jacking up the license plate and putting a new car under it."

[@sshjaguar]

I bought a variac after watching your videos, it seemed so very important to protect me, mine/and others gear, etc they aren't that much I got my that does 30A for $82 brand new.

[@apollorobb]

The only thing you didn't do as a standard practice that i always do it break the hot side of the line in instead of breaking the neutral with the power switch .Great rebuild on the little 5F1

[@michaelwillis8730]

Excellent video! I regret not buying a friend's 1954 Fender Champ back in 1976 as that we would laugh about how long it would take to startup but it had great tone, that along with that I've been thinking about getting a Monotone 5F1 kit I feel much more confident after seeing your video. On the Beckman meters, I too love them. I bought my first one in 1983 a HD110 model and still use it, unfortunately my company mandates yet provides Fluke meters-warning to Fluke users annually Google the Fluke name and model number and the word "recall" as that there have been Flukes that had problems showing false negative readings - meaning it showed the user that there was no voltage yet there was over 400+ volts injuring or killing the users.

[@daveogarf]

Those green below-board jumpers are terribly hard to see on the pictorial diagram! Why didn't they pick purple, or some other color which doesn't blend into the gray so well? LOVE watching these troubleshooting vids - I learn a lot each time.

[@jzcats42]

I wonder if people with color blindness completely miss them. Green and grey are awful similar in certain forms of color blindness.

[@queefersutherland396]

Beckman?! My dad worked there for like 20 years, I think he'd be thrilled if I picked up some vintage Beckman meters from his era working there, I might go pick some up.

[@preiter20]

Another great video with a bunch of quality advice and tips! I'm still in the early stages of learning so tips on when and when not to make changes to existing components is something I usually don't consider, those decisions only come through experience. Thank you for sharing yours with us. Question, when you rewired the board, did you use solid core wire? If so, what gauge and voltage rating? Does the gauge depend on whether it's a filament wire or for plate wiring?

[@Jennifer_Prentice]

Yay loved the video. Great job I approve of the Tidiness of the rebuild lol :). You could not publish too many of these id end up watching them all :). Thanks

[@deepdance111]

For Me....the Best!!! channel to present repair Guitar amp ...Greeting From Poland :)

[@RobBeckett5361]

Great video. Clearly explained

[@andrewclemons8619]

Great video man I learned a great deal

[@Wildman9]

Another fine job Terry.I have a 5F2 amp,made by Allen amplification.Similar circuits for sure great little amps.In fact when I'm jamming with friends ,they always tell me to turn it down.They are quite loud for only 10 watts.Most of their amps are 50 watts of more,and this thing keeps up with those easily.It's got a 6L6,so I'm thinking this thing has to be at least 15watts or more,plus you can change the tube to a EL34 per specs.What I like is this thing weighs only 20 or so pounds.Easy to haul around,my back sure likes it too. I like these videos, you always show your quick tips on what and not to do.Have a good one.👍🎸🔌

[@whatsstefon]

Sounds nice. I've got a box of unmatched output tubes that I was going to use for a 5F2 style amp using 6L6 or EL34 tubes. In single ended form, these tubes are good for about 10 to 12 watts. Which, in reality is enough for 90% of us.

[@dinosworkshop6870]

Great rebuild video!

[@kerryg4119]

I don't like the newer auto-ranging meters. Give me the vintage stuff although I do like the newer capacitance meters. I like to run my main power to my switch and then to the fuse. It's just one more assurance the power is isolated when I'm checking a fuse. Great video Terry. Lot's of good tips in this one.

[@billmiller7138]

You want that cap on the 12AX7, seems it was on most if not all Fender 5F1s. I added it to my clone, nice improvement.

[@tomsteger1]

Excellent video--thank you!

[@ali2ndmail]

Great vid Terry. I admire the effort you put in. It looked hard to work on such a small chassis and that board. I don’t know why the kit doesn’t use a turret board with stand-offs, which would have been nicer. I have a British made kit which uses a nice turret board.

[@DeadKoby]

My last two kit builds, I just followed the layout diagram... patiently, and I got 100% working at first fire-up. If you've NEVER tried one of these kits, I did one on my channel if it helps, but if you can, work under the supervision of someone who's had practice doing this.

[@tomk1tl]

I built my "home made" Fender 5F2a amp from Fender schematics/layout and no issues. I have been doing tech work for more than 30 years so this was easy for me. I also built a stand-alone reverb 6AG15 unit also from Fender schematic/layout and works great ! You do an excellent job at explaining a lot of things especially to "new-bee" builders, etc. Good work Terry ! ! ! !

[@johnsimoes2172]

Nice video Terry

[@MrsG7swr]

I like how you approached this and the thought put into the work done to get some electrical safety into it, and that fuse wiring I hope the ket seller updates that PDQ. Would you consider fitting a class X or above across the line cap to an amp like this? or do you not think there is any benefit? I am very slowly working on an electrical restoration of a Czech built 1950's radio and it has a non safety across the line cap in it so I am trying to decide on if I will go for ceramic or ploly across the line (caps made for the job mind) I think / feel my application needs one as RF is there.

[@christophermarsden9386]

Built the Hoffman amps 5F2A and had no serious issues building it. Loved the turret board that was supplied, it looks better and seems like it will be easier to fix than an eyelet board. One question, would the cap mods for the PS section and the audio section work for the 5F2A?

[@Justplast]

D-Lab your No1 in my book from Down under OZ :)

[@whatsstefon]

Nice work as usual. Is it relatively safe to exceed the maximum capacitance rating of the 5y3 rectum frier? You're only exceeding it by 1uF. But I'd assume it's okay. Probably wouldn't stick a 47uF in there as the first cap though. Good tip for wiring the fuse holder. My scope recently blew a fuse from a recent thunder storm. Upon pulling it out, it gave me a little kiss. I opened the scope and wired it the other way around. Lastly, regarding that cathode bias resistor, I see so many of these clones come to me over biased due to using the stock values, and it seems some amp builders who make these clones think I'm talking rubbish. So, they ignore me by the time I explain that voltages from our mains is higher than it was when these were designed. Plus, they're charging boutique amp prices for these builds. Measure the bias and fit the correct value bias resistor. Somehow, I'm the crazy one.

[@Wade6242]

Great stuff sir

[@daveogarf]

A question, Terry. Why did you go back to the pot-mounted AC switch, rather than clearing a spot on the front panel for the installation of a toggle switch? Your argument for isolating AC from the audio path was well-reasoned and logical, so I wonder why you left it the way it was?

[@Bigjoedo66]

Great Video Terry! Does anyone make a better quality Volume pot with the power switch mounted on the back?

[@jeffcamilleri1422]

You're a legend dude.

[@davekimball3610]

Nicely documented and very educational. One thing I noticed was that your current when you first powered it up after rebuilding it was a bit higher than the current you showed on the Weber site. Is there a certain tolerance that you or in general is expected or allowed?

[@gregjohnson5194]

Your the best Terry

[@jamesgoodin1008]

I hope this makes sense, I’m very new to this. Do the resistors between the first, second and third capacitors need to bumped up in size since the caps were increased?

[@bradrebar101]

Hi Terry really enjoy the vids. Ive been working on a 5f1 and there are a lot of different versions of this amp. Grounding is shown as one way in some versions and as another in other versions. So, what I'm hearing is that the filter cap grounds should be separated from the "signal" grounds? Is there a book that you could recommend to a new amp builder? Thanks!!

[@macgvrs]

Now, it may not be appropriate for this amp, but what are your thoughts on using varistors in the case where you need to use a solid state rectifier in place of a tube?

[@BenPrevo]

If you can find it -- the indirectly heated 6106 is a great sub for a 5Y3 -- the 5V4 as well

[@thomasplooij9795]

Can someone help answer this question of mine? I am changing the caps in my old amplifier and i was wondering if i van replace ceramics for film caps? Does the type of cap hava an influemce kn the sound??

[@christopheraustin8827]

Hi Terry, question for you on the power-up test with the 1k ohm 6V6 cathode resistor. On the power-up test, was it connected, or was it still a floating lead? You said afterward to solder it in. I am just curious, as I am still learning. Cheers!

[@radioengineering8247]

Vintage test gear rocks! It does just as good a job (sometimes better) as the modern shiny units, at a fraction of the cost. In addition, most of the older test gear can be repaired fairly easily - not so with the modern stuff!

[@algio3041]

Would the caps still be underpowered for a diode rectified power supply? I followed uncle Doug’s p2p build and he upped the first cap from 16 to 20uf and left the other two at 8uf. I just ordered all the parts for it some I’m wondering if I should go ahead and put another order in with the higher value caps. Edit for clarification: I’m using diodes because I’m doing a conversation of a champ 600 reissue. The transformer doesn’t have the necessary winding tap for a tube rectifier.

[@vhm14u2c]

@13:33, you mention about using 5y3 rectifier only. If the power xformer did not have a 5v winding, can the 5y3gt be substituted for a 6x5gt?

[@BrianMcNamara1]

Hi Terry My 5F1 amp was buzzing like crazy when I had the black AC wire going to the switch. I re-wired the switch by sending the white AC wire to the switch and the buzzing was gone! It seems that the black wire on the switch must have been inducing a hum into the volume pot. Not sure why Mojotone says it doesn't matter which wire goes to the switch...clearly the white wire is the better choice.

[@matthewf1979]

I don’t think that’s a Mojotone kit. Unless they really cheaped out, that looks like a cheap Ebay kit. I always follow the ORIGINAL Fender layout with the brass ground plate under the jacks/pots. Never have an issue with noise/ground loop. The only changes are the modern center tapped 6v heater wires, which some late tweed amps do have. A cathode bypass cap should be on V1. A 1uf to 8uf really bumps up the gain and limits the bass response. The 50/50 on the 6V6 cathode is fine for 6 and 8 inch speakers. If someone wanted, a custom 10” cabinet is available from Mojotone, then you could increase the V1 and 6V6 bypass caps to 25/25 and 100/50. Using those values with a stock speaker size turns a Champ into a fart box. In my opinion of course. Thanks for the Video, Terry. Great work as always!

[@russellesimonetta3835]

I like the ground buss ala marshall style. Those brass plates develop corrosion over time and screw things up.

[@jameswallace5967]

I'm building a scratch 5F1 and put in an on/OFF switch too.

[@brucemillar3015]

What about diodes and a series resistor to emulate the characteristics of the 5Y3 rectifier tube?

[@ericmorrison794]

Dlab rocks if you want it done right be like dlab and uncle doug.you are the gold standard

[@allsafe1]

Can anyone help ,I am confused by the input jacks i have the pin connections withe the tip being the middle pin ,ground obviously to the part connecting to ground . I have however seen that the outer pin is the tip and the switch is the middle position as is shown in the diagram on this video. Are there differing connection protocols for these switched mono jack sockets .

[@hugomejia593]

Important !Don't forget to connect a speaker cab to not fried the tubes cheers

[@ProfTrout]

Thanks for another great video D Lab - didn't get what you meant about fuse holder safety - you said diagram was wrong showing hot on side terminal then said if hot was on centre post it could shock you through the fuse when unscrewing it, seems like you contradicted yourself, did I get that wrong?

[@KeepsOnBurning]

Great video! Terry, you should learn to play some easy electric guitar riffs.

[@cloudconnect]

I don't have your level of knowledge Terry, but I believe you might be wrong about those back-up diodes on the rectifier spiking current. Since they are placed in series, not parallel, they still get limited by the voltage drop and internal resistance of the rectifier tube, and would appear to not affect the delayed warm up and current flowing ability of an indirectly heated GZ34.

[@CC-te5zf]

What are your thoughts on modifying the negative feedback loop, such as a trimmer pot or some way to dial in the resistance for a particular tone? Thanks!

[@d-labelectronics]

I prefer no negative feedback, adds life to the sound

[@videolabguy]

Thank you for the bias calculator page. Is it me, or have modern kit designers never built a kit? I have seen SOME modern instruction sheets that are so atrocious, failure is guaranteed. It almost seems intentional. Not that you find many people younger than 50 building kits these days. Who can afford them?

[@RobertKohut]

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

[@ewerton8463]

this is a lot more interesting than the radio videos

[@d-labelectronics]

Yes Sir, sorry I will try to keep the mix mostly tube amp repairs, just had a load of radios hit the shop back then

[@chadhawkins2520]

I think a 1uf bypass cap on that preamp would give you more middy sound. 25uf is pretty much a full range boost on that circuit. 1uf should roll off some bass and tighten it up a bit

[@mikesimmons1307]

In this video, you stated not to change the rectifier tube. what would happen if I were to change the preamp tube(s) to lower the voltage going into the output amp?

[@DennisMurphey]

Another 5F1 repair video awesome and more new tips great stuff. I had a old Knight Signal Generator but gave it away, stupid, are there inexpensive high quality tools you can recommend to fill up my bench with stuff i need to setup and diagnose on my 5F1 Amp conversion. I am close to applying power thru tubes. If you see a mushroom cloud over Virginia just light a candle for me. Dennis

[@DennisMurphey]

i have gone thru all your 5F1 videos and made detailed notes of the testing and mods and things to look for. I had powered my 5F1 conversion from an Eico Signal Tracer and had no sounds. I am using a 6X5 Preamp because I had it. I have the 12AX7 and 6V6 tunes as described in your videos. I am so afraid i will blow this up so i am going to follow the no power testing 1st, then Heater power testing, then HV power testing, I hope i find a simple issue as you have in your videos. Extremely useful stuff great appreciate it, I will send you a tip for wine when i get this baby playing. Thank You for all you do. Dennis is ti possible corrosion in the tube socket could inhibit power flow. I reused all the old sockets??? How can i clean them, fine sand paper on a tooth pick???

[@DennisMurphey]

Blew up the 6X5 Rectumfier tube! oh no! I had miss wired the socket {twice} and it must have damaged the tube. Ordered another tube. Oh Man!

[@michaelstokes4497]

Back of the fuse holder and power should/could have some sleeving to prevent accidental electric shock while working on the amp. The rest of the circuit is isolated by the transformer from direct connection to mains supply.

[@danielsaturnino5715]

But Terry, I saw an old datasheet on the interwebs stating max 32 mf of filtering for the 5y3. Can I damage my rectifier by increasing the filtering like you did?

[@crazyuncleduke8012]

Boeing should consult Terry to sort out their problems. :-)

[@russellesimonetta3835]

The under board jumpers get all first time amp builders.thats why i like to just make turret boards. Don,t need backer board. It is elevated above the chassis and i like to drill a little hole next to jumper lands. Route the wire up through the hole and you csn verify the jumper is in and soldered to the turret.

[@bryanbailey6963]

How much time did you spend rebuilding this amp? I've been given one to work on that has a terrible hum, so I am also thinking the best path is to pull it all out and start from scratch rather than trying to chase down the hum.

[@johanneskirchmayr]

which Kit would you recommend for a 5F1 build??? Mojotone??? Weber??? Hoffmann???? Thanks a lot, I am a complete beginner....

[@ArceAngel]

one smart fella

[@PerryCodes]

Plug it in and play it!! What good is a rebuilt amp if it doesn't make some noise!?! Looks beautiful btw.

[@JohnvL]

Thanks again ;-)

[@andrewclemons8619]

Nice hakko

[@kubockferre5532]

hi id like to know how much voltage on the plate of 6v6 thanks

[@boctok55]

What gauge wire did you use to replace the old wiring? The reason I'm asking is that I'm working on an old Laney and the wiring in it seems like it is really small.

[@d-labelectronics]

22ga for the 12ax7 wiring