Newbie: Where to start to read with which I have to start with?

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mcc
Posts: 19
Joined: Sun Oct 28, 2018 11:19 am

Re: Newbie: Where to start to read with which I have to start with?

Post by mcc » Thu Nov 01, 2018 5:33 am

Hi,

but one thing is still in my head:

I saw a flippy mod instruction on Youtube ... and I am scared.

In the FAQ linked above there are given three methods of getting flippy disks being read:
1.) Punch a second index hole into sleeve of the floppy. Scares me, too
2.) Do the flippy mod to your drive. I am scared, still.
3.) Add an magnet to the drive spindel to create kinda virtual index puls. Since this creates
a rotating magnet field inside a floppy drive, which is instructed to read possibly very
aged magnetic signatures from a delicate surface of the same age...I am scared.

Since the index hole is a hole I think, the index hole reading electronic is a light barrier.

When flipping the floppy the original index hole goes to the opposite position...that's why 1.) works.
So...would it be sufficient to add a second light barrier to the drive? Since a photo sensor is high resistant
when not lit it may be even possible to connect both in parallel to the reading electronic.

Or am I already lost again...;) ?

Cheers!
mcc

brightcaster
Posts: 145
Joined: Fri Nov 08, 2013 10:48 pm

Re: Newbie: Where to start to read with which I have to start with?

Post by brightcaster » Thu Nov 01, 2018 10:11 am

You're absolutely right. A second light barrier at the correct position would be fine. Unfortunatelay I have never seen a drive which offered enough space at the correct position. Usually there is some mechanic or the pcb located in that position which can not be removed easily...

David

brightcaster
Posts: 145
Joined: Fri Nov 08, 2013 10:48 pm

Re: Newbie: Where to start to read with which I have to start with?

Post by brightcaster » Thu Nov 01, 2018 10:28 am

BTW: There are drives that have jumpers which (if set correct) let them ignore the index pulse an keep rotating and sending data even if there are no index pulses at all. The Mitsubishi MF504B and MF504C behave this way if you remove the jumper RD for example. Theese drives where recommended for the catweasel system years ago because the catweasel controller could be forced to ignore the index pulses too and so it was possible to read flippy disks B-side without any modification. But I actually don't know if the kryoflux behaves the same?

Other experts may shed some more light on this issue....

David
Last edited by brightcaster on Thu Nov 01, 2018 6:11 pm, edited 1 time in total.

ZrX
Posts: 483
Joined: Tue Dec 06, 2011 9:09 pm

Re: Newbie: Where to start to read with which I have to start with?

Post by ZrX » Thu Nov 01, 2018 3:11 pm

KF absolutely requires the index to have accurate count on the track length. Analysing track length from data alone could be erraneous depending what the track contains, and the actual start of a track would be anyones quess.

mcc
Posts: 19
Joined: Sun Oct 28, 2018 11:19 am

Re: Newbie: Where to start to read with which I have to start with?

Post by mcc » Thu Nov 01, 2018 6:47 pm

Hi,

what's about this:
Take a floppy and draw its surroundings (word?) inclusive the middle hole and the index hole
onto a sheet of paper.
Cut out the drawing so you get a paper mask of the floppy.
Flip the 5.25" drive over and center the middle of the floppy mask over the center of the
flywheel and align the mask.
Mark the position if the index hole on the fly wheel.
Take a very black Edding marker, Sharpy or such and gently press it on the mark on the flywheel.
Turn SLOWLY the flywheel (not to induce substantial voltage and current) while drawing a very black
circle -- this line should be at least of the diameter of the index hole.
Punch a small circle out of a aluminum foil with a paper puncher.
Glue this little aluminum thing onto the black circle using a CA glue for example.
Buy a small reflection light barrier and aim it against the black circle.

This construct ("The Matrix" :) ) doesn't use any magnets so no harm to the sensible floppies.
Since the diameter of the aluminum circle as the radius from the center of the rotation are
identical to that of the floppy itsself, it should mimicry the pulse width and frequency of the
original index pulse.

Would that work?
What do you think?

Cheers
mcc

User avatar
mr.vince
Posts: 2101
Joined: Tue Oct 05, 2010 5:48 pm

Re: Newbie: Where to start to read with which I have to start with?

Post by mr.vince » Tue Nov 06, 2018 8:38 pm

You know there's a way to solve this professionally, right?

Or prove me wrong and build the above and show us that it works! ;)

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