Tube Radio Guitar Amp: Part 2 Plugging in…

After thoroughly checking the internet ressources and mostly figuring out which buttons do what, it was time to fire it up.  First I had to dig out some speakers to at least have some load connected to the output transformers to avoid them burning up.  IMG_5065

Well, incredible enough: the zombie came alive…. and it’s name is Steve Tyler.

Not all bands are working, but that’s not the part we care about anyway: we want to plug in our guitar.  For that we use the PU/phone/GRAM input on the radio.  In my case is was a sort of three prong plug: left signal, ground, right signal.  I salvage a two prong from another radio, had to snap it in two, then soldered one to the tip, another to the lug of an input jack.  Guitar is mono, this radio is from 1965 and a stereo unit, so we only use either left or right channel. You always have to connect to the middle, that’s ground.

IMG_5066Of course, you will also have to switch the radio to activate the phone channel.


Well, the sound when playing through a Epiphone Les Paul is mostly a kind of dog fart like fuzz tone that makes the cat up and hit for the garage, the real buy celexa prices lofi dirty gritty overdriven sound. And the volume is also lacking…

Speakers: I think these are 4 ohm speaker, while the output transformers like to see 8 ohm on each speaker. I am overdriving the speaker and overheating the output transfo’s.  I need to address that issue tomorrow.

Settings: The best tone and most volume is with all tone button disengaged. Mono turned on, but even in that mode, the Stereo Exp. function seems to do something (good).

Power Filter capacitors

These suckers are dead as Zed, after 55 years…no doubt about it.  I didn’t have immediate replacements for the big canned 50uF caps, but a third 8uF cap was much more in reach and obviously in need of replacement:

IMG_5076Here it is located in the schematic as C3:

powersectionI rolled up a home made 8µF/900V cap made up of two 4µF 450V’s in parallel:

IMG_5077And mounted them like this:


This gave me a tad more volume.

Input Resistance

The factory schematic shows 100k resistance in series with the phone jack on both channels. Decreasing the value to 68k (standard input resistance on most Fender amps) also will increase the volume a bit.  You may jumper it altogether, but if you start picking up Russian RF signals, it’s not the radio.




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