Bad heads on RL02: Worth replacing

[Chris Zach]

> I don't believe there should be any contact to make any "wear" affect 
> the head.  It may have been damaged if you're talking one of the heads 
> you cleaned up.  But heads should never really contact the drive on 
> these types of heads.

Thanks Jim: The problem was happening before I removed the head, and the 
symptoms (ring of white dust on the disk) has been going on for awhile 
so I don't think it was the cleaning that threw it out of alignment.

I took a set of watch calipers to the head this morning to see if I 
could measure the head width front to back (where front is the part of 
the head closest to the spindle and back is the part of the head 
furthest). Without removing the head from the head arm it's tricky to 
measure, but it's pretty clear that the ceramic on the rear of the head 
is thicker than the ceramic on the front of the head.

Which would make sense if it was dragging, as the ceramic would be worn 
down by the pressure of the arm spring pushing down more on the front 
than back. Once the head is angled it probably will not fly.

The next question and the really fun one is if the magnetic bar and 
loops that are embedded in the ceramic are above the level of the 
ceramic head. Ceramic on disk would leave wear, but I'll bet that steel 
of the magnet would carve a nice trench.

I'll try to take a picture this evening but in the meantime unless 
someone says that a wedge shaped head is "normal" I'm flagging this one 
as bad.

Thank you for the write-up below. Amazing stuff...

C

> 
> I haven't posted earlier, but I had the same head technology on 
> Microdata and Western Dynex drives.  Those had spring steel welded from 
> the frame that attaches the positioner and the wires run out to the head 
> via that arm.
> 
> The thing I had happen was that in fiddling with the head, and cleaning 
> it, one could flex the head mounting.  It was a very stiff probably 
> stainless steel, but I suspect in cleaning efforts early on when I was 
> working with the heads and drives I got hold of some which either I or 
> someone prior had over flexed.  The clearance is so small that I think 
> that tweek allows the head to look okay, but in actuality isn't flown in 
> the proper orientation to stay clear of the media.
> 
> I built a number of drives up from highly abused parts, and there were a 
> lot of them, so got to play back then and learn.  Huge numbers of media, 
> junk drives and the like.
> 
> Once I got new heads the problems vanished.  Never did get a reliable 
> way to ID a head as good, so I always had a non essential removable 
> platter I'd fit the heads to and fly them to see if they caused damage. 
> If not, I'd move them to the fixed disk on the bottom of the positioner, 
> and mount two more on the top that I'd vetted.  That saved the most 
> media and heads.
> 
> But unfortunately not good now days where media and heads are scarce, 
> since it risks the media and heads.
> 
> thanks
> Jim