NRZI tape recording

Hi,

thank you all for the valuable comments!

After your answers I think that it would be rather simple to build a new drive electronic. Only some amplifiers and some stupid logic.

Now it looks like the biggest problem are not the data electronics rather than the pneumatic system. I have some broken vacuum switches. Need round membranes for them. If anybody has a clue where to buy membranes - please let me know! The gap for the membrane movement is only about 5mm so the membranes need to have a pleat in the right diameter......

How simple! Yes.......

Ok, than the tape in the gap must have been erased. And the first flux transistion on any track is not between full one and full zero or vice versa but between "neutral" and one of the other states, right? That would mean that my to-be-built read amplifiers have to sense "half change impulses" as well.

Here ist what I have understood for now. Please correct me...

For the drive to read a tape properly I need to build: * Seven read amplifiers, made from OpAmps with adjustable high gain (don't know the voltages from the read heads yet) * A kind of rectifier for the pulses from the amplifiers * A rs flip flop for each channel which is set by a phase-change pulse by the rectified pulses * A 7 input OR logic over the flip flops which will generate a data ready pulse * A variable delay on the data ready pulse line

As I remember the data would be present on the flip flops. When the controller gets the data ready pulse it reads out the flip flops and resets them.

Is there anything important that I've not mentioned?

What about the skew? If I add a delay into the strobe pulse I will be able to sample the flip flops in the middle of the bit time. So It can be buttumed that all phase changes for the frame are done and skew doesn't really matter. Is there anything wrong about my thoughts?

BTW my tape drive operates at 200-556 bpi.......

Best regards, Philipp :-)