6G16 Vibroverb - AM I NUTS?

[XYZGnomon]

When I was 12, I made a string of blinking LEDs in shop class. Otherwise, just general troubleshooting continuity with a multimeter is the extent of my practical experience in electronics.

I just ordered https://reverb.com/item/35712510-mojotone-brownface-vibroverb-style-amp-kit because I like a challenge. I have been following some amp repair guys on YouTube for a while - I've learned a lot! - but I don't feel even remotely qualified to actually go through with the build. However, that's never stopped me before!

I'm here to ask for moral support. If you can think of something you wish you knew the first time you did something, what would that be?

[labb]

Take the schematic and the layout and with a highlighter highlight each and every connection/component as you build.

[sluckey]

Read mojo's amp kit primer and disclaimer.

Realize that you will be working with a schematic and a layout. No step by step instructions. No other documentation.

This will take quite a few days. Having a secure, dedicated workspace is very important.

[CascoSieg]

I'm fairly new to this as well, with some long ago experience building Heathkits etc.
I found it helpful to read 3 or 4 build guides, cover to cover, for various kits amps (Trinityamps, Ampmaker, Mojotone, Metropoulos, etc.) to get a general sense of accepted practices, and also to better understand different tactics for accomplishing the same things. The various resources and instructions on Hoffmanamps (https://el34world.com/Hoffman/instructions.htm) also gets right to the point.
Things I do more consistently now than when I started: test every component prior to installing it, unit test for expected resistances and voltages as I go, start over on something if it begins to look messy.
Best of luck and have fun!

[labb]

Take a read through this. May be worth your time.

Microsoft Word - P1-HO-P1eX Build Guide 05.10.15.doc (ax84.com)

[tubeswell]

Get some good amp building tools


Assorted pliers including small spring loaded wire clippers and needle-nose pliers for working in confined spaces


Wire stripper


A couple of soldering irons (a pencil-tip 40w for most of the soldering and a high-wattage 80+W with a flat tip for high-heat soldering) and solder flux.


A reliable multimeter with high voltage insulated probes/leads and assorted other leads with insulated clips - handy to have one that measures capacitance if you are new to electronics.


Assorted screwdrivers and spanners and/or socket and wrench set


A lamp nut spanner thing


And for the odd bit of metalwork (getting sockets to fit in holes etc)


Drill and assorted bits


Assorted smallish metal files (flat and round)

[Medley]

I built the same kit this past spring. Great amp when it's finished, but check your parts kits very carefully. I found I was missing a number of important components. In particular, make sure that they included the 470R carbon composite resistor. In mine it wasn't included, but the problem was that the small parts box didn't even have a spot for it so I didn't know I needed to look for it. You'll also find a couple of inconsistencies between the layout sheet and the schematic. Nothing major, but be prepared to do a little problem solving.
Also, I found that the 15k grid bias resistor was way too high in combination with the 10k bias adjust pot to be able to get the negative bias voltage high enough to get a proper bias. I ended up replacing the 15k with a 6.8k. You may find otherwise but that was my experience.
Check your components before you install them, and check your work thoroughly as you go along. Good luck.

[dwinstonwood]

A lamp nut spanner thing

 

Also, round-nose pliers for making neat U-shaped bends in wire, and a couple of clip-on heat sinks to protect components when soldering.

[XYZGnomon]

A lamp nut spanner thing

 

Also, round-nose pliers for making neat U-shaped bends in wire, and a couple of clip-on heat sinks to protect components when soldering.

I coincidentally just ordered https://www.knipex.com/products/electronics-pliers/electronics-pliers/electronics-pliers/3532115 & https://www.knipex.com/products/electronics-pliers/electronic-super-knips/electronic-super-knips/7803125, so thanks for the suggestion!

EDIT: WRONG LINK ON ROUND TIP PLIERS; NEW LINK IS CORRECT

[XYZGnomon]

I built the same kit this past spring. Great amp when it's finished, but check your parts kits very carefully. I found I was missing a number of important components. In particular, make sure that they included the 470R carbon composite resistor. In mine it wasn't included, but the problem was that the small parts box didn't even have a spot for it so I didn't know I needed to look for it. You'll also find a couple of inconsistencies between the layout sheet and the schematic. Nothing major, but be prepared to do a little problem solving.
Also, I found that the 15k grid bias resistor was way too high in combination with the 10k bias adjust pot to be able to get the negative bias voltage high enough to get a proper bias. I ended up replacing the 15k with a 6.8k. You may find otherwise but that was my experience.
Check your components before you install them, and check your work thoroughly as you go along. Good luck.

Thanks! I have some good news and some bad news: The good news is that I will be building a tube amp, and I will hopefully not be in over my head with an advanced project... because I decided to start out with something smaller: The StewMac '57 Tweed Mini, also known as the 5F1 Champ. I cancelled the Mojotone order, which did not have a firm ship date and would take at least a month or longer for some reason. The StewMac kit shipped same day.

The bad news is the StewMac kit is wildly overpriced, since the same kit from Mojotone (I am not convinced Mojotone is real yet LOL) and similar ones elsewhere are a few hundred dollars cheaper. They emphasize their instructions as being unique to StewMac and particularly good, however I watched the video livefeeds on YouTube and there were some questionable orders of operation.

I am going to build it and I'm going to learn something, have fun and have an amp (finally!) in the end, so there really isn't any bad news!

[thetragichero]

everything at stewmac is grossly overpriced. never purchased a kit from mojotone but i've bought chokes and tolex and can caps from em. they're one of the sites where you can sign up for their email list and get 15% off, right? if so do that

[acheld]

StewMac's instructions are very good -- they usually are available for download, so you can check it out pre-purchase.

[Fresh_Start]

Make sure that you find detailed start up procedures and follow them, including using a light bulb current limiter.

Chip

[Latole]

StewMac's instructions are very good -- they usually are available for download, so you can check it out pre-purchase.

I look at them, they are very well made, like Heatkit long time ago.

XYZGnomon practice soldering on scrap pieces of wire before to work in the amp.

[dude]

Building an amp “kit” is like painting by numbers. Make at least two copies of the layout. Follow the layout, on another copy mark a dot on the layout after you soldered each connection, pay attention to how many wires go to one point on the layout, only solder when that point matches the layout, same number of wires to a turret, eyelet, pin, whatever.
Go slow, never rush or work when you’re tired. 9 out of 10 if you follow the layout, you will succeed, check each dot on layout and the board, chassis or whatever you soldered each time you start working. You can never check the dot marks enough.
Someone above suggested highlighting on the layout, that’s good for the third copy. Also, after putting a dot on the layout put one on the actual bd., pin or terminals, you can always remove the dots on the board with a Q-tip and alcohol, use a sharp point marker, black is good.
Have confidence, painting by numbers is all it is in the beginning and being 100% accurate, no room for mistakes but we all make them.
Use light bulb limiter for first start-up, search Sluckey’s or Hoffman’s info for how too info.

[Medley]

I built the same kit this past spring. Great amp when it's finished, but check your parts kits very carefully. I found I was missing a number of important components. In particular, make sure that they included the 470R carbon composite resistor. In mine it wasn't included, but the problem was that the small parts box didn't even have a spot for it so I didn't know I needed to look for it. You'll also find a couple of inconsistencies between the layout sheet and the schematic. Nothing major, but be prepared to do a little problem solving.
Also, I found that the 15k grid bias resistor was way too high in combination with the 10k bias adjust pot to be able to get the negative bias voltage high enough to get a proper bias. I ended up replacing the 15k with a 6.8k. You may find otherwise but that was my experience.
Check your components before you install them, and check your work thoroughly as you go along. Good luck.

Thanks! I have some good news and some bad news: The good news is that I will be building a tube amp, and I will hopefully not be in over my head with an advanced project... because I decided to start out with something smaller: The StewMac '57 Tweed Mini, also known as the 5F1 Champ. I cancelled the Mojotone order, which did not have a firm ship date and would take at least a month or longer for some reason. The StewMac kit shipped same day.

The bad news is the StewMac kit is wildly overpriced, since the same kit from Mojotone (I am not convinced Mojotone is real yet LOL) and similar ones elsewhere are a few hundred dollars cheaper. They emphasize their instructions as being unique to StewMac and particularly good, however I watched the video livefeeds on YouTube and there were some questionable orders of operation.

I am going to build it and I'm going to learn something, have fun and have an amp (finally!) in the end, so there really isn't any bad news!

Good for you, and probably a good idea. The 5F1 is a basic circuit with not a ton-o-parts as has the 6G16. They also sound great. The reason Stew-Mac's kits are overpriced, IMO, is because they get some of their stuff (cabinets, possibly chassis) from Mojotone, as do many "boutique" builders. They have to make some margin on what they paid Mojotone, obviously. And I can assure you Mojotone is the real deal (I think you were speaking with your tongue firmly planted in your cheek, but just in case...). The Vibroverb kit was the second I'd bought from them, the first being a 5F4 Super I built last year. Their lead times are a bit long (longer since the Pandemic), but that's because they're a really large operation that supplies people like us, but also OEMs, the custom builders, etc. I think I read a while back that they supply cabinets, chassis, etc, to 45% or more of the other builders in the US.
Enjoy your Champ!

[waldner]

XYZ,


I just finished this 6G16 Vibroverb build and it's a really nice kit.  Mojotone does a very nice job of packing and organizing all of the parts.  You do need to have some experience though as there are no instructions.  I've build several of Doug's layouts (which I prefer) and used mostly turret boards (which I also prefer) but I wanted to build a complete vintage style combo amp so I decided to give this a try.   The Mojo kit is a fender style layout with eyelet boards, just like the original amps.  The layout is a bit cluttered and tricky, and the eyelet boards took a bit of getting used to for me, but it wasn't too bad.  I got stuck a couple of times and nice guys like Slukey on this forum helped me out. 


I decided to get everything from Mojo other than tubes, which I have lots of, and speakers, which I ordered separately.  I went with a mixed pair of Jensen P10Q and C10Q for a bit of added sonic complexity.  The Mojo cabinets are very nicely made too.  Highly recommended when you feel you are ready for it.   I've attached a couple pics of mine.

[Medley]

XYZ,


I just finished this 6G16 Vibroverb build and it's a really nice kit.  Mojotone does a very nice job of packing and organizing all of the parts.  You do need to have some experience though as there are no instructions.  I've build several of Doug's layouts (which I prefer) and used mostly turret boards (which I also prefer) but I wanted to build a complete vintage style combo amp so I decided to give this a try.   The Mojo kit is a fender style layout with eyelet boards, just like the original amps.  The layout is a bit cluttered and tricky, and the eyelet boards took a bit of getting used to for me, but it wasn't too bad.  I got stuck a couple of times and nice guys like Slukey on this forum helped me out. 


I decided to get everything from Mojo other than tubes, which I have lots of, and speakers, which I ordered separately.  I went with a mixed pair of Jensen P10Q and C10Q for a bit of added sonic complexity.  The Mojo cabinets are very nicely made too.  Highly recommended when you feel you are ready for it.   I've attached a couple pics of mine.

Hey Waldner, congrats on getting 'er done! Where did you get the faceplate?

Here's picture of mine with an authentic Fender original name plate. I'm still trying to figure out what I want to put on the silkscreen. I've got a bit of an eclectic brand thing emerging and would sort of like to have my own "brand" silk screened into that space on the faceplate.

Nice amp, eh?

[waldner]

I found the faceplate on eBay.

[XYZGnomon]

XYZ,


I just finished this 6G16 Vibroverb build and it's a really nice kit.  Mojotone does a very nice job of packing and organizing all of the parts.  You do need to have some experience though as there are no instructions.  I've build several of Doug's layouts (which I prefer) and used mostly turret boards (which I also prefer) but I wanted to build a complete vintage style combo amp so I decided to give this a try.   The Mojo kit is a fender style layout with eyelet boards, just like the original amps.  The layout is a bit cluttered and tricky, and the eyelet boards took a bit of getting used to for me, but it wasn't too bad.  I got stuck a couple of times and nice guys like Slukey on this forum helped me out. 


I decided to get everything from Mojo other than tubes, which I have lots of, and speakers, which I ordered separately.  I went with a mixed pair of Jensen P10Q and C10Q for a bit of added sonic complexity.  The Mojo cabinets are very nicely made too.  Highly recommended when you feel you are ready for it.   I've attached a couple pics of mine.

Cracking good job! Thanks for showing it!

[waldner]

I built the same kit this past spring. Great amp when it's finished, but check your parts kits very carefully. I found I was missing a number of important components. In particular, make sure that they included the 470R carbon composite resistor. In mine it wasn't included, but the problem was that the small parts box didn't even have a spot for it so I didn't know I needed to look for it. You'll also find a couple of inconsistencies between the layout sheet and the schematic. Nothing major, but be prepared to do a little problem solving.
Also, I found that the 15k grid bias resistor was way too high in combination with the 10k bias adjust pot to be able to get the negative bias voltage high enough to get a proper bias. I ended up replacing the 15k with a 6.8k. You may find otherwise but that was my experience.
Check your components before you install them, and check your work thoroughly as you go along. Good luck.

Not sure if this will help you but I was unable to get mine in the proper bias range either and Sluckey helped guide me to increasing the bias rage resistor, which is the 1K on the small board in series with the diode.  First I tried going to 1.5K and that wasn't quite enough, so I went up to 2.2K and that was perfect.  Now mine is putting out about 17-18 watts and sounds great.

[XYZGnomon]

Things are starting to arrive in boxes! I have all of my soldering gear now, including two diameters of 60/40, wicking, snips, round pliers and THIS!

[Latole]

First soldering iron. Start by learning how to solder.
Don't learn on you amp project. Bad solder are aways a issue for a beginner

[dwinstonwood]

I like to work in a well ventilated area when soldering, especially with lead solder.
Some people use fume extractors: https://www.amazon.com/Fume-Extractor-Soldering/s?k=Fume+Extractor+Soldering

[pdf64]

I like to work in a well ventilated area when soldering, especially with lead solder.
Some people use fume extractors: https://www.amazon.com/Fume-Extractor-Soldering/s?k=Fume+Extractor+Soldering

My understanding is that lead fumes  / gaseous lead inhalation when soldering, is a complete non issue.
The operator protects themselves from lead by following good hand hygiene. eg use of barrier cream before each work session, and washing hands after each work session, and before eating, drinking, smoking, using toilet.
Fume filtration / extraction is to mitigate the hazard of occupational asthma, due to inhaling flux fume, primarily rosin based types.
Tin lead solder with non rosin based flux works great, is much safer to the operator, and is readily available.
But doesn’t smell as nice 

[PRR]

> and THIS!

What, a black & white LCD monitor?

There's a huge difference between a 2mm 4 second puddle for hand-solder, and the all-day yard/meter-wide solder lake for felt-hatters or PCB wave-dipping. Also between 40hr/week wage-work and hour/month hobby labor.

Rosin allergy is a very real thing. Rare, but if you have it then you maybe should not solder.

[XYZGnomon]

QUESTION ABOUT WIRING:

Do you guys approve of the StewMac 5F1 layout for the mains? It seems to contradict what I have seen on popular YouTube channels, and I'd like to get a consensus here before I solder it in.

EDIT:

I am specifically talking about this method of wiring in mains (omitting the accessory socket) from Uncle Doug: https://youtu.be/dIR6AT1etXM?t=1277 START AT 21:17

EDIT 2:

Psionic Audio contradicts Uncle Doug here: https://youtu.be/LEmicVit420?t=798 START AT 13:18

Should I put the fuse before the switch or the switch before the fuse???

[sluckey]

You paid a premium price for a quality kit that has excellent instructions. Because of your knowledge and experience level, I highly recommend you follow the Stewmac instructions EXACTLY. There's nothing wrong with the way Stewmac wired the mains. Stay away from youtube until you complete this kit.

Even though I don't disapprove of Stewmac's wiring, I would never do it like that. Here's the way I would do it, but don't listen to me either!   

[XYZGnomon]

Here's the way I would do it, but don't listen to me either!   

I promise, I won't do it like that. 

[acheld]

Yah, YouTube is not your friend now.  Stewmac's instruction (which are excellent) is your buddy.

[XYZGnomon]

Stewmac's instruction (which are excellent)

...isn't as perfect as you might think. They supply brown/blue/green power cord, but show black/white/green in the instructions. Also, I think the order of operations is a little weird; if I had done a couple of the solder joints their way I would have had to solder underneath and behind something.

I'm happy to learn from others and take good advice, and that's why I joined el34! Keep 'em coming!

[sluckey]

Brown = black = 120v
Blue = white = neutral

[PRR]

US cords used to be black/white. (Black was once FAR cheaper, and I've worked in all-black systems.)

The rest of the world gravitated to blue and brown.

The US cord makers withered, and we have been buying "World" power cords with the blue and the brown.

Electrons are color-blind. And your wires are not going around the house to the far bedroom, all inside the one chassis. Just be consistent.

Green is green. Even if they add a yellow stripe.

[XYZGnomon]

I found another inconsistency between StewMac's instructions and reality: the keys show as between pins 1 & 8 (correct) and the fastener holes between 3/4 & 7/8, but the alignment of the fastener holes don't match the Belton sockets IRL; they are between 4/5 & 8/1.

They're clocked wrong in the instructions - 45 degrees out! That means I have to follow the numbers and ignore the graphic staring at me... or do I follow the graphic and ignore the numbers?

EDIT: I ADDED A PHOTO FROM THE SAME PERSPECTIVE AS THE GRAPHIC.

[PRR]

Follow the numbers.

[sluckey]

You found nothing. The fastener holes have absolutely nothing to do with the key. Heck I have some sockets that are mounted with tension rings that allow the fastener holes to be rotated anywhere around the actual socket.

The key is always located between pins 1 and 8. Look at the socket from the bottom. Find the key. The first pin that is clockwise of the key is pin 1. Continue counting clockwise. It's nice to have the pin numbers stamped next to the pin but don't rely on those numbers. I've seen some numbers whose location was quite confusing as to which pin the number is associated with and could lead you down a rabbit hole. But the key location will never lie to you.

[XYZGnomon]

The first pin that is clockwise of the key is pin 1. ...the key location will never lie to you.

Thanks! That answers my question, but they still screwed up the graphic enough for me to ask the question before I proceeded. I'm glad I asked, because you just gave me enough information to understand it in context, which is important.

[sluckey]

You will notice the key on the little tubes is a wide space. Looking at the bottom of the socket the first pin clockwise of the key (wide space) is pin 1. Following the key is the "key" to a successful socket wiring. 

[XYZGnomon]

First time go. It works!

[XYZGnomon]

All of the AC & DC voltage values from the book were within 10%, and some were EXACTLY the same number.

In the end, I made 3 minor modifications:

1) Fuse/switch wiring
2) Speaker jack to Switchcraft 11 & plug to 280
3) Chickenhead knob off at 6 o'clock (Goes to 11!!!)

Things I wish I could change:

1) Terminal strips buried under the fuse and pilot lamp housing
2) More green wire - I used every last inch, and I was lucky I cut it the way I did
3) Power transformer nuts aren't covered by my Klein 5-in-1 nut driver
4) IEC socket would have made the wiring less complicated
5) Some of the assembly sequence steps assume I have smaller hands

Things I learned:

1) I don't have three hands
2) Each pretty solder joint is a small victory
3) Trust the tube socket indexing key over the graphics in the instructions
4) People have wildly differing opinions about what right looks like

[shooter]

Things I learned:

I find those are just as enjoyable as the sound from a good working build!
and you do have a 3rd hand, it sets between the 2 you have, typically used for speech, but it'll hold a wire, solder, extra parts......

[sluckey]

Things I learned about tweed style chassis:

     NEVER BUILD ANOTHER AMP IN THAT STYLE CHASSIS!