I am in desperate need for a solid state (Non tube) tape head record preamp and bias circuit for a 1/4" NAB 3.75 ips RCA Victor tape cartridge player/recorder, I was able to salvage two identical mono playback only preamps from two Fedelipac cartridge players but I still need to be able to record and erase, I was looking to salvage one from an old 8-track player or real to real but the technology is so old that most of them have capacitors problems, Any modern good quality DIY or assembled kits out there ?
Here you go:
OTARI CTM-10R Cart TAPE CONTROL CTM-10A RADIO BROADCAST Professional VINTAGE PRO | eBay
Everything but the erase head and 3.75 IPS EQ.
I must admit to being confused as to why you'd want to do this....
OTARI CTM-10R Cart TAPE CONTROL CTM-10A RADIO BROADCAST Professional VINTAGE PRO | eBay
Everything but the erase head and 3.75 IPS EQ.
I must admit to being confused as to why you'd want to do this....
It's a nice find but I will have to figure out all the wiring diagrams and how to isolate the rec/play preamp from the rest of the electronics.
As to why I want to do this? I want to be able to playback and record on RCA cartridges its that simple.
Full documentation is available. That is broadcast equipment meant to be serviced by an in-house engineer. The manual is a full service manual. The most you'd need is mating connectors and wire, possibly a control mod to take the place of the transport deck it worked with. It's actually the cheap and easy way, just unfamiliar to you.
...and that oscillator should be low distortion, symmetrical, and switched cleanly without transients, with one output for erase head, another variable output for the record head. You could cheat and forget the erase head and erase your carts with a hand held bulk eraser, which is what was done with most broadcast cart recorders as the carts don't have a place for a third head.
The Otari record amp has all of this already, plus record EQ, meters, and input level controls.
The Otari record amp has all of this already, plus record EQ, meters, and input level controls.
Definitely not European (no idea why you'd think that), US NAB. 3.75 ips EQ is a time constant change in the EQ circuit, likely changing a resistor and/or a cap or two. But the hard part- the amp, EQ, and boss oscillator are done.
Look, you wanna build this all from scratch, that's fine, go nuts. It's basically all done for you with this thing, but perhaps that's not the point. I don't see much ch advantage in cannibalizing a reel to reel deck, unless you find one really cheap, you'll still need a service manual. I do recognize you'll have a hunt for the connectors and manual, it's really not plug-n-play. But I'm not too sure what the point is, so...
Not really caring here. Just understand what you're rejecting.
I was trying to explain that I need to be able to erase tracks independently that's why I said I need the erase circuit, I'm not capable of building an erase circuit by myself therefore I need something ready with minimum modification, I see your point of bulk erasing but I'm not erasing an entire tape at once. You are asking me to change resistor and capacitors and the other guy telling me to build an oscillator, If I know how to do all this I would have built my own amp.
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Yup, got it. Here's a few things you may not realize.
The heads you have are, from left to right, erase, then record/play. The same head is used for record and play, which means you'll need to build up a switching system that transfers the head from the play amp input to the record amp output. Are you up for that?
Next, setting up and equalizing the system. Normally a tape deck is first adjusted to play back a test tape properly. That's done by adjusting play level and the play equalizer to play back the reference tones properly, while observing their level on an oscilloscope or meter. For stereo machines, the play head must first also be aligned to the test tape for best high end frequency response and inter-channel phase response, which is a mechanical adjustment of the head physical position. This requires an oscilloscope. Once the play side is set up, you work on the record side. Two head decks are harder than 3 head decks because you need to record tones, then rewind and play them back, then record again making small adjustments. You start with bias level, adjusting for a peak in output at 1kHz, then you go for record EQ which is adjusted so that test tones play back properly.
Are you up for any of that? Got the test gear? You'll need at very least a tone generator and oscilloscope.
Next, you'll have some mechanical issues to deal with, which actually should probably come first. Got good pinch rollers? Capstan motor work smoothly? Belts? Brakes? The slip-clutch take-up drive? Not much point in doing the electronics if none of that's working well.
To simplify the project, you could get a 1/4 track stereo reel-to-reel deck (working) that runs at 3 3/4 IPS and record your tapes on that, then take the cartridge apart and load your tape in. Then just adjust the head and play EQ for the best sound by ear, at least you'll come close and don't need any special gear.
For reference, here's a few shots of a fully restored unit I saw last November. Note the price. Ask yourself how close you could come to a full restoration and get that value from your efforts, see if it's still worth doing.
The heads you have are, from left to right, erase, then record/play. The same head is used for record and play, which means you'll need to build up a switching system that transfers the head from the play amp input to the record amp output. Are you up for that?
Next, setting up and equalizing the system. Normally a tape deck is first adjusted to play back a test tape properly. That's done by adjusting play level and the play equalizer to play back the reference tones properly, while observing their level on an oscilloscope or meter. For stereo machines, the play head must first also be aligned to the test tape for best high end frequency response and inter-channel phase response, which is a mechanical adjustment of the head physical position. This requires an oscilloscope. Once the play side is set up, you work on the record side. Two head decks are harder than 3 head decks because you need to record tones, then rewind and play them back, then record again making small adjustments. You start with bias level, adjusting for a peak in output at 1kHz, then you go for record EQ which is adjusted so that test tones play back properly.
Are you up for any of that? Got the test gear? You'll need at very least a tone generator and oscilloscope.
Next, you'll have some mechanical issues to deal with, which actually should probably come first. Got good pinch rollers? Capstan motor work smoothly? Belts? Brakes? The slip-clutch take-up drive? Not much point in doing the electronics if none of that's working well.
To simplify the project, you could get a 1/4 track stereo reel-to-reel deck (working) that runs at 3 3/4 IPS and record your tapes on that, then take the cartridge apart and load your tape in. Then just adjust the head and play EQ for the best sound by ear, at least you'll come close and don't need any special gear.
For reference, here's a few shots of a fully restored unit I saw last November. Note the price. Ask yourself how close you could come to a full restoration and get that value from your efforts, see if it's still worth doing.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Piece of cake, I'm aware of all this.
I initially wasn't planning on doing this thinking a 3.75 ips NAB preamp should be ready to go, But if it's a must I don't have a problem with it, I have an app for tone generator, I will use my DAC with my phone to get a clean line level tones, As for the oscillo. I can get a cheap one or a USB type one.
The mechanical part has been taken care of, Everything is cleaned, lubed and adjusted to the spec.
This is not a restoration project, It's more of an improvement fun project, Whatever money spent here pays for the fun.
Too bad they don't make such preamps anymore for DIY, There are tons of tube type that are worth a fortune though.
Ok, Finally I found and ordered a record/playback preamp board along the power supply board for an Akai GX-4000D. It's a single board everything is in it, I will come back here when I get it for calibration help.
I posted a detailed thread at Tapeheads forum for this project with pictures, If you happen to be a member there you can check it out, Didn't get much help there but I like to visit that forum very often.
I posted a detailed thread at Tapeheads forum for this project with pictures, If you happen to be a member there you can check it out, Didn't get much help there but I like to visit that forum very often.
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