Bakelite Princeton Amp
28 Dec 2008
This was my first attempt at building a valve amp, and my first time working with high voltage. A learning experience, to say the least! I took a metric shitload of photos during the build, so this is going to be a primarily pictorial write-up.
I saw these photos of a 1940’s AWA Radiola Model 510H radio on eBay and figured it would make a pretty cool guitar amp:
Radio front
Radio back
Radio guts
I had first considered converting the existing radio amplifier circuit for use with guitar. Unfortunately the ancient components all needed replacing, the output transformer was pathetic and the power transformer was just plain dangerous. So, I gutted it and used the chassis as a basis for an entirely different amp – a “brownface” Fender Princeton.
Out with the old!
Clean up ~70 years worth of rust
Having decided what amp I wanted to build, I needed to plan how it was going to fit into the chassis and the existing holes…
Click image for larger view
The layout dictated covering some of the octal valve sockets with a steel plate and punching smaller noval socket holes in their place. A healthy coat of JB Weld and some nuts & bolts did the job nicely:
So far, so good…
A few coats of spray enamel later
Test-fit of all chassis hardware
Then came the fun of building the circuit. First I wired up the filaments, then power supply and filtering, tone/volume pots, phase inverter and finally the tag strips in the middle containing the majority of the capacitors and resistors.
Ready for final testing
Finished; rear view
Finished; front view
After many hours of head scratching and debugging, it’s alive!