6G3 Brownface Fender Deluxe: Mojotone Amp Kit Build Walkthru & Tips

Donny Danger walks you through the build of a Mojotone Tube amp kit; specifically constructing a "6G3" Fender Brownface Deluxe replica.
Donny discusses the amp circuit topology, reviews the supplied parts in the kit, proposes some suggested modifications, and gives some "build tips" based on his previous experience.
Note: As legend would have it, this is the type of amp that was allegedly used on the first few ZZ Top albums as well as the seminal blues ballad: "Cat Scratch Fever" by one Theodore Nugent.
00:00 start
02:23 build documentation
03:07 schematic overview
07:50 proposed modifications
17:24 chassis mechanical and grounding
23:49 couple build tips
27:06 supplied tubes and component packaging
29:58 filter caps wiring
31:17 circuit board stuffing
34:45 wiring tip
36:42 heaters and output tube wiring tips
39:20 ac wiring details
41:09 ground connections
43:08 final look over
43:42 biasing notes from startup
47:34 final thoughts and critique

[@RobertNolan]

Last thing I needed was encouragement to build one of these lol maybe i need to do it. This was a very interesting and in-depth walk-through. Thank you!

[@rockdanger]

If it is your first time maybe try one of their tweed deluxe or champ kits that have step-by-step instructions... get your confidence up.

[@RobertNolan]

@@rockdanger it's not my first time around population circuits, I've also done breadboarding, but it would be my first amp build. I think I may be able to handle this one.

[@emmadoodoo2]

I just received this exact kit from mojo with the 1x12 cab. This is an excellent video and will help me with the build. Thanks for posting!

[@rockdanger]

Glad it helped... good luck on the build.

[@goodun2974]

The cabinet was probably made taller than most Fender head cabs so that it could be used for a Bandmaster Reverb as well as a regular Bandmaster. The reverb tank needs to be farther away from the transformers then it would be in a regular Fender head cabinet, otherwise you'll get hum radiating into the reverb transducers, which are electromagnetic, similarly to guitar pickups.

[@rockdanger]

Yeah I've seen one of those band master reverbs in the wild; quite the monster... seems like that was an overkill design on sender's part as lots of modern heads have the reverb pan packed in there tight and seem to make it work.

[@edwardebel1847]

Thanks for this video...been taking all the D-Lab suggestions...nice of you to mention him. The brass ground plane seems to be the way to go. My Blackface Deluxe is in progress...going slowly and carefully. For the brass shim stock, I clamped it to the back of the chassis front with a strip of wood the full length...just drilled right through the brass and the wood. D-Lab recommended a stepper drill bit for the final hole drill, and that worked for me. Thanks again...

[@rockdanger]

Yeah, Terry @ dlab seems to really know his stuff. Highly recommend his channel / videos.

[@goldenboy8167]

Great video! And good timing for me as I am considering building this for my first amp. I was bummed to see that it doesn't include the step by step instructions like their tweed deluxe. Maybe with the help of this video I could handle it!

[@rockdanger]

If you know how to solder it should be doable... recommend checking your finished chassis against the schematic with a highlighter before you power on. Also, would be good if you have a local amp tech to help you out if you get in trouble.

[@edwardebel1847]

I'm building the Deluxe Reverb Blackface and had the same problem with no step-by-step. But I looked at the Princeton Reverb documentation and there is a step-by-step for that, and there are a lot of steps that are similar, like wiring the tube socket heaters. Also strongly recommend D-Lab 5 tips for success with the build. Good luck

[@goldenboy8167]

@@edwardebel1847 Thanks! I was thinking about looking at the other step by steps that Mojotone has as a guide. What is D-Lab?

[@rockdanger]

Yes... if you review the mojotone tweed deluxe step-by-step there should be a lot of common concepts and same general order of operations. They also have a build series up here on KZbin showing a guy stepping thru a blackface deluxe build

[@rockdanger]

Dlab is an ampbuilder channel here on youtube... search and you should be able to find... he's got a ton of great videos up.

[@TheStephensjoshua]

Great Info. Thank You

[@rockdanger]

Thanks for watching... I was thinking nobody would

[@sharkair2839]

what a cool video.

[@rockdanger]

Thanks brutha!

[@roncarter2188]

Very nice kit! I've heard that the pio caps sound great for the coupling caps from the phase inverter to the power tubes. They came from Russia, I think I'm going to try them in my next build.

[@rockdanger]

Let us know how they work out for ya

[@samchipner1131]

I just did one of these and when you solder your brass plate to chassis I had to scuff the chassis .it seemed to help .my deluxe came out nice . Peace

[@rockdanger]

Good tip! Thanks.

[@goodun2974]

A green kitchen scouring pad will word for cleaning oxide film from brass and other metals prior to soldering; every electronics hobbyist should also have a fiberglas-bristle "scratch brush" for cleaning terminals before soldering.

[@goodun2974]

This is a pretty good tutorial, but, using a transformer mounting bolt for the bias-supply ground is *dangerous to the existence of the amplifier*. Those nuts loosen over time, from transport shock, speaker vibration, and expansion/contraction of the bolts. If that bias ground is intermittent, you can blow up output tubes in a minute and perhaps take out some transformers with it. I know Fender did that way, but it was a poor idea and it's not reliable for the long term. Either drill a hole for a dedicated grounding bolt or solder the wire directly to the chassis (this goes double for the green power cord ground wire; bolting it to the transformer isn't safe and DOES NOT MEET MODERN ELECTRICAL CODE. Mojotone should know better, and should provide a dedicated ground lug. I dont want to see anyone get hurt, nor do I want to see lawsuits from someone getting electrocuted. Also, although your soldering of components to the board looks good, and your wiring layout is generally okay, it's clear from the closeup of the brass ground plane at 41:14 that *your soldering iron is completely inadequate for making those ground connections*. I'm sorry to have to tell you this; but I've got over 50 years of soldering and repairing audio electronics under my belt, and those solder connections to the brass plate are obviously cold-soldered and unreliable. You need to buy a heavy duty, high-wattage soldering iron or gun and redo those grounds, including the bias-supply and earth ground. Good soldering directly to the chassis will make the amp safe, reliable, and low-noise.

[@rockdanger]

I do not dispute anything you say sir... thanks for the input.

[@goodun2974]

PS, what type of solder are you using? Leadfree, probably supplied by Mojotone? Leadfree solder has a higher melting point than leaded solder, and doesn't wet and flow as well as leaded solder does. It's particularly difficult to make chassis grounds with leadfree solder, especially with a marginally suitable iron that isnt hot enough. Also, shine up the brass with a scotchbright pad before trying to solder to it ---- it probably has a greasy oxide layer.

[@rockdanger]

Mojotone doesn't supply any solder with kit... I use good old fashioned lead-containing stuff and try to do my best bill Clinton impersonation., (ie try not to inhale)

[@goodun2974]

@@rockdanger, leaded solder and it's fumes pose little danger of poisoning because the boiling (vapor pressure) point of lead is about 600 degrees higher than the melting point of lead solder. It's a good idea to wash your hands after soldering, and don't handle food at the workbench; but the oxide film that forms on lead solder isn't water soluble and isn't likely to be absorbed through the skin. Some people find the rosin flux fumes to be irritating, and a small percentage of people are allergic to, it but otherwise it isn't toxic. I've been breathing the stuff my entire life with no apparent damage attributable to it. The fluxes used with lead-free solder, on the other hand, are very irritating to the nostrils, perhaps even toxic, not to mention corrosive and electrically conductive.

[@Glensully]

And you didn’t bloody play it

[@rockdanger]

Yeah I did... separate 36min playthru demo is up on my channel... check it out.

[@Glensully]

@@rockdanger i only wish that had a spring reverb :)