RL02 head replacement, disk back online

[Chris Zach]

So after looking at the mess the mice had made of my third RL02 drive I 
decided it would probably be better to pull the heads and put them in my 
second drive (the one with the bad top head and plugged filter).

Getting heads out was simple, and I decided to put them side to side 
with the heads in drive 2. The following images show some interesting 
details.

https://i.imgur.com/tcmkUmO.jpg

Note that O is original (the heads from drive 2) and the top heads are 
from drive 3.

First, the heads on the third drive were in pretty good shape and looked 
clean. Under the loupe though I could see some fragments of gunk that 
needed to be removed. More importantly I did a side view comparison 
between the bad top head in #2 and the top head in #3:

https://i.imgur.com/D6HOxND.jpg

This was a really tough picture to take, and you have to zoom in on the 
heads in the upper right. But what you can clearly see here is that the 
better head from #3 (left one) is pretty much rectangle shaped while the 
crashing head from #2 (right one) is shaped like a wedge, with the top 
part being narrower than the bottom.

https://i.imgur.com/fEGuOFE.jpg

And of course the filter removed from #2. Note the silicon sludge, I 
think this is 100% blocked (and was why the drive made a lot of air/wind 
noises when spun up, the fan was cavitating)

This sums it up: I think what happened is the unit was run in a very 
dirty environment, the absolute air filter plugged up, and the heads 
don't fly as well without that blast of clean air coming in. So they 
dragged on the disk, and the ceramic rubbed off (and onto the packs) 
which led to the eventual disk damage.

Moral: Change filters. I cleaned up the #3 heads, put the heads from #3 
into unit #2, put the air filter from #3 into #2, and fired it up with 
the test pack. Goes to ready no problem, will do a full dir/bad with 
RT11 later this afternoon to see if I still have two errors on the pack.

It is interesting to note that the bottom head from drive 2 didn't look 
too bad, and did not pick up any dirt/oxide from the disk after I 
replaced the filter. It was probably flying very close to the platter 
but had just enough airflow to make it fly. Still, I'll put it in the 
spares pile and think about it for awhile...

Otherwise, back in business. I'll be checking the filter on #1 just to 
be on the safe side. It was my RL02 drive from 30 years ago and was not 
one of the Solarex ones. Then I'll put fixing this third RL02 on the 
calendar (will need new wiring, long ribbon cable, filter, heads, and a 
massive clean-up inside), and start working on restoring my darn RSX11M 
4.2 disk packs...