Custom recording bias circuit?

[juanh58]

Recently got a vintage (mistreated) Sony cassette recorder and had the idea to turn it into some kind of a portastudio, attaching a Tascam head I had lying around. Everything works fine (playing the four tracks of a tape) but the circuit I used for this, taken from the cassette player part of a Philips mini system, doesn't seem to provide the correct bias values for making it record anything.
Well, I (kind of randomly) replaced some resistors and some capacitor and it actually recorded some noisy input, but the thing is that I don't have an oscilloscope to test how the head is behaving, much less the knowledge in electronics to know what else to do exactly
As you see, I got carried away with this mod, trying to enjoy the learning process, and got stuck.
I'm attaching my circuit here, hoping that someone would point where to play around there... or could I use some external bias source?
My intention is to record one track at the time. It's kind of a creative/arty project by the way
(also there's the tascam head, couldn't find it's impedance or other info)

 

[hopey]

It's an interesting subject but your just stabbing in the dark. I think you have to use an erase head before you lay down fresh tracks.

 

[juanh58]

It's an interesting subject but your just stabbing in the dark. I think you have to use an erase head before you lay down fresh tracks.

hey thanks for your reply... i'm in the dark, slowly learning, but I appreciate any help.
I guessed the player's original fixed magnet would be enough here. I didn't try it with new tape, but with used ones it only got as far as recording a fraction of a second of barely audible signal, then fading

 

[juanh58]

Didn't mention it but I only intend to record only one track (mono) at the time. Also, was afraid to test the impedance of the new head (with a simple multimeter, some say it may magnetize the head) but did it anyway. I got 160 ohms/track.