New here and looking to build a tube amp

If you want to build a tube amp you should start with a kit. I am partial to Franklyn Amps so I will recommend the company in the link below. You can also purchase a very nice cabinet from them.

https://www.franklynamps.com/shop/p/5f1-chassis-kit

 

The chassis? Sure, the rest of it not so much... You can't just add a power transformer into a transformerless amp, the filament voltages are very different from tubes used with a power transformer and while you can run it through an isolation transformer that is still problematic.

For the same reasons, standard guitar amp schematics are not going to be easy to adapt to those tubes, so you're going to need to design this amp from the ground up if you're insisting on using the tubes and output transformer from your tabletop radio and that is it's not going to be a simple task and therefore probably does not lend itself well to a first project.

A kit, or at least building a clone of a classic amp, is probably a better place to start for your first build unless you want to spend a lot of time learning what you need to know to design a circuit from the ground up.

 

I would find a radio with a transformer and some more guitar amp like tubes. It would be way easier. Radios out there with 6v6 6k6 power tubes. And 6sn7 and tubes of that family for preamp.
Hammond organ conversion is a well tracked path. I think it would take a lot of research/learning to go with what you got. I don’t know where you live, for me lots of old radios and such on kiji/Craig’s list for 25-45$ That are a easy slide int a guitar amp. Easy to learn what is guitar friendly.

 

Here is a something I bought for $20 it was a radio.
The amp was separate from the radio, this is the amp. Power and output transformer 5y3 rectifier 6v6 power tube. The third sockets had a plug going to the radio. The two wires are the speaker wires Minimally it needs a preamp tube in the place of plug socket. New guts power cord and and a input jack, you are playing guitar. Something like this is the perfect starter radio to guitar project. It is even the right shape to go on a cab for a combo.

 

Welcome to TDPRI

 

Spend some time learning some things here:

https://robrobinette.com/How_Amps_Work.htm
https://robrobinette.com/Champ_Micro.htm

Any idea what kind of amp you want to build? How big is the radio chassis?

 

Having just finished a Bassman Micro as my first build, I can say that Rob's designs and instructions are well documented and sound great. Easily worth the time and effort.

Having repurposed an old chassis, I learned that you likely need to have a chassis somewhat bigger than you would otherwise need. Any holes that do not line up with the new layout may cause adjustments to how things are mounted. I guess if you are going really old school and not using any boards for your components then this may not apply. I thought my chassis was more than large enough because it had more tubes than the new circuit, however the layout combined with the existing holes for things like a cap can, etc. ended up making for somewhat of a tight fit front to back. One side of my board ended up being right under the pots on the front of chassis. Overall it was worth it to me, because even though it would have been easier and nicer looking to buy an new chassis to use I wanted to use the old combo amp with a 15" speaker.

 

Should be plenty of room for a simple amp in there.

I built a 1-ish watt amp head with a 6sj7 preamp (different implementation than the 5c1, but same tube) in an old radio. I liked the sound quite a bit.

 

Here's links to a schematic, layout and parts list for a 5f2a (Tweed Princeton). Great amp, love mine and had fun building it.
https://el34world.com/Hoffman/files/Hoffman_5F2A.pdf
https://el34world.com/Hoffman/files/Hoffman_5F2A_BOM.pdf