Members gardo Posted September 12, 2017 Members Share Posted September 12, 2017 I'd give it a go for $5 He plays with the radio for the first 8 min then plugs a guitar into the audio in jack on the back [video=youtube;FFKebDPwC40] Link to comment Share on other sites More sharing options...
Members Chordite Posted September 12, 2017 Members Share Posted September 12, 2017 As long as there is an earth leakage circuit breaker in the supply.The really old wooden cabinet tube radios have beautiful tone, especially on male voice Link to comment Share on other sites More sharing options...
Members gardo Posted September 12, 2017 Author Members Share Posted September 12, 2017 As long as there is an earth leakage circuit breaker in the supply. Good Point Link to comment Share on other sites More sharing options...
Members WRGKMC Posted September 12, 2017 Members Share Posted September 12, 2017 Just because somethings old or uses tubes doesn't mean there's going to be any worthwhile mojo there. Unless you know what you're doing its a bad idea to mess with old table top radios. I cut my teeth on old consumer gear making them work for guitar so I know first hand what I'm talking about and know what's involved too. I used to convert many radios over to amps and the results usually sucked badly depend on the radio design. Some of the bigger Am/FM, Shortwave sets that had push pull amps sometimes sounded good but the single ended table tops were usually too weak to be of any use. I had better results turning them into intercoms. The old AM radios ran the tube filaments on AC voltage in series straight from the jack. This means one tube goes out they all go out. 90% of the circuitry and tubes are for the radio portion, not for audio. Downsizing the circuitry to make it an amp only is highly impractical and the audio portion is usually garbage. If the radio's old it usually unreliable. Hum is usually a big issue and it doesn't pay to recap the thing even if you can find the right component values which are usually oddball stuff. Even the speakers often had oddball impedances to match their non standard transformers. ( there were no fixed standards back in the 50's 60's on allot of consumer gear. Power caps used in those units can be very difficult or impossible to find. Old radios can be very dangerous to mess with too. I cant count the times I've been zapped with those bastards, by all rights I should glow in the dark. Most old table tops use two way wiring and use a grounding cap (death cap) for the chassis. Plug it in backwards and you have 120V on the chassis. It would need to be wired for 3 way grounded plug and all caps need to be replaced. Most of the wiring can have insulation that's liquefying at this point. Plastics from back in that era begin to break down becoming an electrical hazard if not outright time bomb. The power caps are usually a 2 or 3 way electrolytic cardboard tube type set in wax. If its original it needs to be replaced to get rid of AC ripple. (even then it may only have a half way rectification which is garbage) Other problems, you're lucky if the power amp has 1 watt of power and it doesn't have a preamp for instrument level. Its at best, line level and even when you disconnect the radio section, you have to add additional preamplification to get the guitar loud enough. to drive a speaker. The speakers often had the output transformer mounted on the speaker instead of the chassis. If the speaker is original it likely suffers from dry rot. A guitar signal driven up will blow it into to chunks. Overall - without the additional preamp gain stage, the circuit design, the need to make the circuit safe rewiring the AC, adding a new speaker and possibly output transformer, the results simply wont justify the effort nor the cost. The audio quality is likely awful too. If you were adding a mono line input, Its relatively easy to connect a switched jack to the volume control wires to disconnect the radio tuner from the amplifier, but its really not a project for a beginner with no experience. Safety being may major concern for you. I used to build radios as a kid and converted many desk top radios add a line level input for a phonograph or tape player. Audio quality usually sucked pretty bad on most table tops. I'd often have a pair (or more) so I could run stereo from the turntable. The two sides didn't come close to matching in audio quality, but it was my hobby to tinker with radio back in the 60's, and later it became my profession. If this was an old Hi Fi that had higher wattage you might have enough wattage there to survive the re-voicing of the tone stack. Hi Fi and radio are full frequency and guitar needs to have, not only an extra gain stage, it needs to have the amplifier voiced for guitar pickups. Without the re-voicing its going to sound like mud lacking mids and too much bass and treble. What I suggest, if you're serious, disconnect the radio signal input from the volume pot and connect a 1/4" jack to the amplifier at the pot. Then use a pedal that can gain the guitar up to line level and see what it sounds like. There are many preamp pedals available. Dan Electro makes one for around $12. This will give you a strong enough signal to drive the amp and let you know what it sounds like. If it sounds good to you then you can go about adapting it even further. If it sounds like crap, then you haven't wasted allot of time and effort in a failed project. Link to comment Share on other sites More sharing options...
Members gardo Posted September 12, 2017 Author Members Share Posted September 12, 2017 All I'm saying is that I would pay $5 for it just for kicks.If I ruin it or it doesn't work ,so what, I would just throw it out. Link to comment Share on other sites More sharing options...
Members r0bo01 Posted September 12, 2017 Members Share Posted September 12, 2017 doesn't sound half bad. might be good for recording if that was the desired sound. p.s. - it did have an rca input jack and switch... Link to comment Share on other sites More sharing options...
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