Mojotone 18 watt TMB using chassis and transformers from a Valve Standard

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wade
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Mojotone 18 watt TMB using chassis and transformers from a Valve Standard

Post by wade »

Long time guitar builder I am now going into deep water. I have been inspired by Uncle Doug and guys here on 18 Watt. A lifetime ago I was studying electronics even then, tubes were not covered in any of my courses.

I have an Epiphone Valve Standard that I am tired of repairing. I have purchased a Mojotone 18 watt TMB small parts kit, will try to use the transformers from the Epiphone and this will be my platform to begin to learn the art of building tube amps. I would appreciate if anyone can recommend a really useful book specifically addressing design considerations/explanations of the guitar tube amp.

I started with this.
1a.jpg
The layout of the Valve Standard’s face plate is well suited for the 18watt TMB. Only had to add two holes, one more for another input jack and one for the pilot light.
1.jpg
All the wiring is complete. I am afraid my work with dressing and wiring is not as pretty as the builders here are. I can see that is an acquired skill.
2x.jpg
11axs.jpg
After a quick test of voltages with the tubes out, I put some old tubes in for a smoke test. To my surprise everything is working, both channels and all volume and tone controls. There is little to no hum. The amp has great volume. I will be checking all the voltages and computing plate current to learn how to do this…I am following Uncle Doug’s videos on this.

I will say, based on the many heath kits that I have built many years ago that the instructions and documentation from Mojotone could stand a bit of improvement.
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Last edited by wade on Sun 08/08/21 7:28 pm, edited 1 time in total.
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JMPGuitars
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Re: Mojotone 18 watt TMB using chassis and transformers from a Valve Standard

Post by JMPGuitars »

Welcome to the site!

Glad to hear your first project is going well. I highly recommend reading the instructional threads in my signature below. Also read the safety page linked on the homepage.

A word of caution: Uncle Doug is a mixed bag. I'm not personally a fan. Some of his advice is dangerous (potentially lethal), so please be careful with his videos. Some of his info is good, but there are significantly better sources if you want to see tech videos on youtube.

Reading through this website will give you a plethora of information. You can also check out Randall Aiken's website, and Valve Wizard (Merlin)'s website. Both are great. Merlin also has a good book regarding amp design.

Another popular book is Design and Construction of Tube Guitar Amplifiers by Robert C. Megantz.

If you want to see some much better videos on youtube, check out Mr Carlson's Lab. I don't remember if he has much tube stuff on there, but he has a LOT of great content.

EDIT: Rob Robinette's site and bias calculator is also good stuff: https://robrobinette.com/Tube_Bias_Calculator.htm

Thanks,
Josh
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wade
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Re: Mojotone 18 watt TMB using chassis and transformers from a Valve Standard

Post by wade »

Josh,
Thank you very much for the references. I read your instructional threads before I began my project. I have attempted to implement your recommendations on the ground scheme. Will hold off on my questions until I spend some time searching the site. Again thank you very much for your input. As a long time member of a guitar builders site I know it gets very tiring answering the same questions over and over.
Wade
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Re: Mojotone 18 watt TMB using chassis and transformers from a Valve Standard

Post by JMPGuitars »

wade wrote:
Sun 08/08/21 8:10 pm
Josh,
Thank you very much for the references. I read your instructional threads before I began my project. I have attempted to implement your recommendations on the ground scheme. Will hold off on my questions until I spend some time searching the site. Again thank you very much for your input. As a long time member of a guitar builders site I know it gets very tiring answering the same questions over and over.
Wade
lol, that's why I made those threads. ;) ;)
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'I installed a skylight in my apartment yesterday... The people who live above me are furious.' - Steven Wright

Modern Ground Schemes
Soldering Technique
B+ Voltage Reduction
Amplifier Tools & Parts Info


Web Design: DolceVittoria.com
Guitars / Amps / Effects: JMPGuitars.com
(anti)Social: Facebook · Instagram
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