headphone mod. contains GE trannies

[darron]

i just got some retro headphones off ebay. they have leather cuffs. they have a built in AM radio with two knobs on one phone. the volume knob also has a SPST power on/off switch. i was thinking of building a guitar headphone amp inside of them since they have their own 9v battery compartment too. cool huh? i was going to design something all germanium with tropical fish caps etc. when i pulled it apart i noticed the radio/amp actually has 4 GE transistors in it...

there are:
SANYO 2sb187 (green dot)
2sa329 (red dot) x2
2sb186


almost seems a shame to pull it apart. anyone big on radios that thinks that maybe i could/should just bypass the radio part and hook straight into the amp part of it? i'd be interested to get some thoughts on what to do with it.






i guess i'll hack it apart. make a new pcb for it that uses the three original trannys for distortion and amp. use the volume knob as a level and on/off knob, and the other knob for gain..

[GREEN FUZ]

Great idea. You could probably even use the original cable to plug straight into the guitar jack. That`s presuming there is a cable but if it was just a radio there probably isn`t one.

[JDoyle]

You are going to want to locate the oscillator and shut that off before you use it as an amp. It should be the circuit located around the inductor, if there is one. I know relatively little about radio, but it has to have an oscillator...

[darron]

Great idea. You could probably even use the original cable to plug straight into the guitar jack. That`s presuming there is a cable but if it was just a radio there probably isn`t one.

There's a switch on one side to go from normal headphones to radio. It's got one of those old 3 pin plugs, but I could drill it out and replace it with a standard 6.35mm socket.

You are going to want to locate the oscillator and shut that off before you use it as an amp. It should be the circuit located around the inductor, if there is one. I know relatively little about radio, but it has to have an oscillator...

It's times like these that I wish that I had a scope. I can't see an inductor on there. The coil on the ferrite? The oscillator probably uses at least one transistor too I suppose. Gut it I reckon. Could be a while before I get around to it though.

[JDoyle]

It's times like these that I wish that I had a scope. I can't see an inductor on there. The coil on the ferrite? The oscillator probably uses at least one transistor too I suppose. Gut it I reckon. Could be a while before I get around to it though.

The ferrite is the place to look for sure. It should be connected to a vaiable cap (which is also most likely the tuning control) and it will form a 'tank' that tunes the radio.

Good luck!

[darron]

It's times like these that I wish that I had a scope. I can't see an inductor on there. The coil on the ferrite? The oscillator probably uses at least one transistor too I suppose. Gut it I reckon. Could be a while before I get around to it though.

The ferrite is the place to look for sure. It should be connected to a vaiable cap (which is also most likely the tuning control) and it will form a 'tank' that tunes the radio.

Good luck!

yeah. it has that massive variable cap in the middle for the tuning. i understand the concept of a radio, but i've never really built or examined one. so should i maybe make an audio probe and poke around on one side of the variable cap, the cut out all the guts before it and just hook the guitar line in at the 'output' side of the variable cap? there doesn't seem to be anything on these headphones on the net, let alone a schematic