RK05 head alignment -- how difficult?

Philipp Hachtmann hachti at hachti.de
Mon Jul 24 04:33:33 CDT 2017

Hey Fritz,

> As some of you know, I've recently restored a PDP-11/45, RK11-C drive
> controller, and an RK05 drive.
Nice. My 11/45 is not doing anything meaningful...

> I've been inspecting and cleaning packs as I go, and have avoided
> mounting any packs that have signs of significant crashes (e.g. full
> rings down to the shiny aluminum) or any that have corrosion "pox".
What are "corrosion pox"? Probably something you can clean away.

> Other packs have had just little "black smudge" style head crashes
> that come off with some determination with kimwipes and alcohol.
Black smudge seems to be parts of the air path's rotten foam. They're 
annoying. But you can get rid of them.

> Occasionally
> the drive will make a sort of "deli slicer" sound -- I run and unload
> the pack, disassemble it, clean any new smudges, open up the drive,
> give the heads a good inspection and clean, and continue on.  It's a
> little painstaking...
My procedure is: Clean the disk as good as possible. No black stuff is 
allowed to remain. Then I load the disk and manually "scrub" it using 
the heads on the spinning disk. If the "deli slicer sound" is not too 
frightening, I wipe the disk a few times until it goes away. The sound 
comes from dusk applied during cleaning I think.
After the pack runs silently, I unload it and clean the heads - which 
usually have collected some dirt again.

> As I've gone through this process over a number of weeks the heads
> are accumulating dust and oxide in places that are hard see and get
> to,
Hard to see and get to??!?

>  I guess I'm looking for some advice/calibration from the
> community here.  Is it:

> "OMG, are you nuts, don't take the heads out, you'll never get them
> aligned,"
I never pulled and realigned heads. But: I also did not have to!
I did servo adjustments and repairs. In one drive I repaired the optical 
servo system - one of the glasses had fallen off. That drive will need 
adjustment to regain pack interoperability...

> "Meh, RK05 alignment is not really that tough, and you would be
> better off making sure your heads are thoroughly clean and intact."
I heard that it's doable. But it's still work.

I think that pulling out heads for cleaning is generally not a good idea.

How I clean RK05 heads:

Take a cleenex, folded once. Soak it in IPA 100%. Then I load the heads 
onto it. Cleaning by gently pulling the cleenex from side to side.
Usually that's enough. If there are really nasty residues, I use a match 
to scratch it off. Then cleenex loading again.
I sometimes also use toilet paper or whatever I have at hand.

I never ruined a drive so far. It's my standard procedure.

Have fun with your drive!


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