Cheap donor amp for 18watt build

[_ej_]

I have a populated 18watt board and all the hardware for a build minus the chassis and transformers. To buy a chassis and transformers I'd be out at least $300. I figured there might be a used tube amp I could snag for around that and get at least a head cabinet out of the deal. Any old Bugeras or VHTs that would work?

I understand that the quality of the transformers wouldn't be amazing but the reason I have the 18 watt board is because the 18 watt I built wasn't for me (I reworked the build as an AC15).

It seems a shame to just leave all the parts in a bin when having another amp around would be much better.

[ok_state_blues]

Are you in the US or international? Do you need the EZ81 rectifier or can you make do with diodes?

[_ej_]

Are you in the US or international? Do you need the EZ81 rectifier or can you make do with diodes?

US. I have the tube socket for the EZ81 but could live with diodes. I think the Bugera V22 might fit the bill.

[maxkracht]

If the 18w wasn't for you, you should figure out why. There are nearly infinite permutations of what an "18w" means, there's a whole forum dedicated to it.

When selecting a donor amp, the first thing you need to look for is what tubes are currently in it. If that amp has different, or a different number of tubes, you need to figure out roughly how much current the power transformer can supply. Adding tubes and pulling too much current can overheat the transformer and/or lower the output voltage, subtracting could raise voltages.

Next look at how everything is mounted and how much room you have. Are the tubes pcb mounted in weird places? Is there enough room for the board you are trying to save? Will the board need to be oriented in a weird way that will be noisy, unreliable, dangerous?

In my opinion, trying to fit a premade board in another amp not meant for it likely isn't worth the trouble, especially if you didn't like it in the first place. The board and parts on it usually aren't the expensive or time consuming part of a build anyway. Not saying you can't or shouldn't try if you think it would be fun, just be aware it is likely not going to be easy.

[_ej_]

Yeah, I understand it will be a whole different type of project. That's part of the fun.

I've been looking for dual EL84 amps for the very reason you highlighted, making sure the transformers are appropriate.

I want to figure out an 18 watt that works for me. If I can get a Bugera V22 (or something similar) for $150 that's a lot less of an investment to play with a circuit that initially I didn't love.

[patrick620]

I have successfully made many 18 watt Lite IIb amps using Hammond AO-35 organ amps.

[sluckey]

The Hammond AO-39 is another fine donor for the many 18W EL84 amps out there. I built an 18 Watt Lite II-B and a Vox AC-15 Lite in the AO-39 chassis. Here's the link...

https://sluckeyamps.com/hammond/hammond.htm

I've also built a Dual Lite using AO-39 iron but a new chassis.

And here's an 18 watt Vox Double Shot.

[solderhead]

In my opinion, trying to fit a premade board in another amp not meant for it likely isn't worth the trouble, especially if you didn't like it in the first place. The board and parts on it usually aren't the expensive or time consuming part of a build anyway. Not saying you can't or shouldn't try if you think it would be fun, just be aware it is likely not going to be easy.

Sometimes building an amp into a chassis that doesn't "fit" the look or sound of the original chassis can be great fun in it's own right. Back in the late 80's we used to have informal contests on Ampage where we would gut junk amps and build new circuits into the carcass, with the only rules being that all of the front panel controls had to be preserved and had to function as they were labeled. There were no premade boards back then and we had to do all of our own wiring. There were some tremendously great amps that came to life during those days. If you've been doing this long enough then you'll remember the days when nobody cared if you molested a Blackface Bassman.

[solderhead]

the Bugera V22 wouldn't be a bad platform for modding. It's basically a half-sized PV Classic 30. Steve Ahola spent a lot of time developing mods for the Classic 30 that were well documented on his site.

[maxkracht]

Sometimes building an amp into a chassis that doesn't "fit" the look or sound of the original chassis can be great fun in it's own right.

Indeed, i've done plenty of that kinda work. (I've only gutted and rebuilt a BF bassman once, and only because it was a lost cause aside from the iron and faceplate...) Being unsure of the OP's experience level, just wanted to give a bit of warning incase he didn't know the potential challenges. The premade board is the bigger issue in my opinion, but plenty of ways to get creative with that as well. Nice build, by the way.

[nuke]

Find a trashed Blues Junior. It is a good size, already an 18w amp with a 12" and there are basket cases out there, since Fender used the worst possible quality PCB's in them.

[maxkracht]

Blues jr is a good call. Heads up that you will need to find a way to mount the tubes, holes won't be quite right for regular tube sockets. There are aftermarket PCBs that are better quality, or you can come up with another way to mount regular sockets. Here's a pro jr where I used an aluminum plate.

[nuke]

Nice mod.

Yeah, the easiest way to homebrew into the FBJ is replace the tube board with a new one. I see aftermarket boards with double-sided, plated-through-holes on Reverb for under $30 with sockets (you assemble) for a higher quality board. A thrashed FBJ will certainly have a trashed tube board.

Mounting your pots will be the next challenge. All doable though.