Alps A05R data
 

Does anyone have any data sheets on the Alps A05R cassette head?

Markings are Japan A05R, and is an auto reverse cassette head, each of the four coils measures measures dc 220-225 ohms.

I couldn’t find a spec online, but maybe I don’t have the right search terms.

Re: Alps A05R data
 

Dont forget to demagnetise the heads after testing them with a multimeter!!! Thats a no-no with tape heads as you will magnetise them using DC.

Just a heads up

Joe

Re: Alps A05R data
 

Thanks Joe, I hadn’t even considered that.

I’m trying to put together a digital cassette recorder to use with retro 8 bit computers, but direct connection to the head instead of record and playback through the audio circuits of a cheap cassette recorder. It’s probably going to be a lot of trial and error, but a datasheet on the head might give a good starting point for experiments.

Basic idea is to record by driving positive and negative current in square waves to record two flux states on the tape, and in read mode to detect positive or negative pulses for the flux transitions. This is probably going to leave the head magnetized after recording so I probably need to build in some kind of demag circuit before trying to read the tape, or keep the record current low enough to try and avoid leaving too much residual flux in the head.

Would using a high frequency, eg 100kHz, with positive or negative bias be better?

Re: Alps A05R data
 

This brings back memories of the old Sea Data cassette logging system which was designed by Winfield Hill (co-author of The Art Of Electronics). It was a very robust and reliable system using high quality data cassettes which were physically very similar to standard cassettes. It used a stepper motor directly driving the capstan with the data recording synchronised to the steps. It had 4 tape tracks across the width of the tape. There's a picture of the mechanism at

https://www.researchgate.net/publica...e/figures?lo=1

but I've not been able to find any details of the electronics yet.

Re: Alps A05R data
 

You might want to look at the schematics (official and reverse-engineered) of the HP9830 'calculator' which does essentially what you are trying to do. There is no bias that I can see.

Re: Alps A05R data
 

I have the schematics and data for a phillips MDCR that I used to have but unfortunately I got rid of it during the move to canada. I’ve also been referring to the article on saturation recording from Byte january 1977 that I also used to get the MDCR working on a z80 homebrew back in the mid 80s. The MDCR was very similar to a stringy floppy but used a mini cassette and was spool driven.

I’m trying something similar but using standard cassettes, spool driven with a separate dc motor for each spool, rather than the idler arm arrangement used by the MDCR. As standard cassettes have a larger ratio between full and empty spools than the mini cassette, I’m driving the take up spool with PWM and sensing the voltage across both dc motors in feedback control. This part seems to be working as it currently takes about nine minutes to get to the halfway point and the same to the end of the tape. This is with a C90 so just over twice normal speed, which might be OK, but the undriven spool is jumping a bit at the start of the tape and probably needs a bit more damping. Reducing the resistor thats providing electrical breaking doesn’t seem to help much at the start of the tape. I might try changing the drive ratio and increasing the motor speed.

Next step is to try and rig up the head with some adjustment for alignment and azimuth, then see if I can guess at some reasonable drive levels. The PET C2N circuits might help with this.