Hello fellows!! I've recently got into cassette tapes and would really like to build one from scratch. I managed to find the Toshiba TA7668BP, which seemed to have some documentation and a reliable source of purchase. However, I'm stuck reading the diagrams as I don't quite understand the "moon-shaped" and "headlight" symbols in left side of the diagram. I tried to research here and there but nothing pops up. I suspect they are playing head and erasing head but I'm not sure and wouldn't want to risk damaging the heads. If anyone has seen anything like this or knows what they represent, could you please help me out? I've attached the reference circuit as well as pin definitions if that helps. Huge thanks to everyone!
Looks like this is a commercial circuit that switches the electronics between record and play, making the "headlights" either a microphone or a line input, and the "crescent moons" the playback heads. Wouldn't be my first choice when building from scratch (too much mechanical switching), but I'm grumpy. Not shown is any provision for erase, connection and biasing of record heads, etc.
All good fortune,
Chris
All good fortune,
Chris
It is most probably a built-in electret microphone for recording, and a playback head. As used in microcassette dictaphones.
Headlight is electret mic.
Moon shape is combined head.
As Chris said, combined electronics for playback and recording with too much switching.
If chip is cheap, build two separate circuits, with only one swith for head.
Generally its low fi stuff.
Moon shape is combined head.
As Chris said, combined electronics for playback and recording with too much switching.
If chip is cheap, build two separate circuits, with only one swith for head.
Generally its low fi stuff.
Indeed, a playback (or combined) head and some kind of microphone; external dynamic microphone or built-in electret microphone capsule. Even though it isn't shown, a normal electret microphone capsule with built-in JFET would either require a resistor to the supply or have a third terminal that is to be connected to the supply.
Interesting how they say "RECORDING HEAD". Why didnt they just draw another moon shape symbol there? Why instead of the moon shape, didnt they simply say "PLAYBACK HEAD" with a female input arrow instead of an undesignated artsy-fartsy symbol?
Nothing like consistency across schematic diagrams...
Nothing like consistency across schematic diagrams...
Thx everyone for all the information regarding this circuit. All of them are super helpful. I think it's probably better to provide some context and more detailed questions after receiving feedback from all of you
1. I'm not building the mechanical system (using an existing deck from an old tape recorder), but only the circuit to make some sound(which after some research, should consist of preamp, bias, ALC etc..)
2. I wanted to be able to finish this project in 3 months. Do you guys think it's wise to use an IC designed for tape recorders vs doing everything from scratch? People mentioned there are some other chips available, which one would you recommend?
3. This project intends to be an art project, so Lo-Fi is acceptable! Yet if there's a better way to do certain things, please let me know.
4. What's a good place to look for an erase circuit, or any circuit regarding tape recorder? ideally, I wanted to use DC/AC but I could always fall back to a permanent magnet
Again huge thanks to everyone for the input! I'm getting more in this forum in hours than researching on my own for days.
1. I'm not building the mechanical system (using an existing deck from an old tape recorder), but only the circuit to make some sound(which after some research, should consist of preamp, bias, ALC etc..)
2. I wanted to be able to finish this project in 3 months. Do you guys think it's wise to use an IC designed for tape recorders vs doing everything from scratch? People mentioned there are some other chips available, which one would you recommend?
3. This project intends to be an art project, so Lo-Fi is acceptable! Yet if there's a better way to do certain things, please let me know.
4. What's a good place to look for an erase circuit, or any circuit regarding tape recorder? ideally, I wanted to use DC/AC but I could always fall back to a permanent magnet
Again huge thanks to everyone for the input! I'm getting more in this forum in hours than researching on my own for days.
yes, you are perfectly right about this. I failed to find a complete circuit of a tape recorder that I could replicate. Some Chinese manufacturers are still building tape recorders based on this chip, which made me think that it might be a good place to start. Please let me know if you are aware of such a resource, I'd be more than happy to look into it.
Martin
this sounded like a good idea! I was going to use some modern IC to do single pole, n-throw switching to compensate for the original mechanical switch. I think your solution is probably better as these chips only cost $0.1 dollars.
Martin