22 Nov
2009
22 Nov
'09
6:30 p.m.
On Nov 22, 2009, at 5:46 PM, John Ball wrote:
You have to replace the various "gaskets" that were made from that
foam in order to get the proper airflow through the drive so that the
heads "float". Failure to replace them will result in a head crash
due to insufficient air flowing over the heads. I replace them with a
closed cell foam (what was used originally was open cell foam).
Closed cell will tend not to turn into black dust. I use closed cell
weather sealing that you can find in most hardware stores. It has the
advantage of also having an adhesive strip on one side to have it
adhere.
I've been meaning to do a writeup (with pictures) on how to do this on
RK05's but time constraints have prevented it. The one thing you want
to do is make absolutely sure that you've cleaned all of the old foam
and adhesive off. It usually involves some disassembly of the drive
around the airflow channels to be able to get at the parts (they're
easier to clean once they're off the drive). All of the time is
involved in getting the old stuff off. I can now put new foam in a
drive and have it running again in about half an hour (any additional
time is spent getting the old stuff off).
I've been selling nice (tested) 11/34 cpus for ~$350. Expect an 8/e
to be in the $1000's (those I don't have spares of).
TTFN - Guy
If the
head/voice coil assemblies have been removed you'll have to go
through the entire alignment procedure which requires a special
alignment pack. You'll also want to make sure that all of the
dreaded
"DEC foam" has been removed and replaced or you're heads and packs
won't last long. You'll also want to look at the filters and make
sure they're in good shape and replace them (if you can find them).
However, bad filters will also kill the heads and packs.
If the head/voice coil assemblies have been removed how do you know
that the drives are working?
I noticed that foam almost immediately, I cleaned up the majority
but I'll
probably go over the thing with a scraper and the air compressor. I
got the
same nasty foam in my SGI Crimson.
Well at the very least the drive powers up with no nasty smells or
noises or
the fault lamp and I can get the spindle motor to spin up They're one of the standard DEC lamps. I
don't recall off the top of
my head what the equivalent lamp # is but they (or a reasonable
facsimile) are readily available.
Awesome, that might be a bit better as well.
For an omnibus PDP-8 you need an RK-8E controller
that goes in the
omnibus chassis. The "hard" part is finding the cable that goes from
the RK-8E and the drive. For a PDP-11 (unibus) you need an RK-11D
controller. It is actually a 4 board set in it's own backplane that
goes in the CPU chassis. There is also an RK-11C for unibus but that
controller is of the "old style" that has 40 or so flip chips in a
rack width backplane and is mounted outside of the CPU chassis in a
rack (requires a separate power supply) that connects to the CPU with
unibus cables.
Hmm, that might be a bit of a problem as I never see spare flip
chips or
anything unless they are on ebay for funky prices.
If you're not looking for a
"blinken" lights machine, you're best bet
would probably be an 11/34 system. I have several that are "spares"
but right now I'm swamped and haven't been able to spend any time on
classic computer stuff.
TTFN - Guy
Well right now I'll go for pretty much anything. I guess a 34 or
similar is
a good starter system and on some distant day I'll switch to say an
8/e.