27 Nov
2012
27 Nov
'12
7:50 a.m.
On 11/27/2012 06:33 AM, Chris Elmquist wrote:
On Monday (11/26/2012 at 01:38PM -0500), Allison
wrote:
NOS rollers are sill OLD and shot. The only thing is NEW build.
When new the roller had a hardness close to rubber tires and
when they started to fail they would finger nail dent easily.
On 11/26/2012 12:29 PM, Chris Elmquist wrote:
Correct. These rollers were not
gooey in any way on inspection.
They were NOS replacements I ordered from a DEC parts supplier.
On Monday (11/26/2012 at 06:56AM -0700), cctech
at vax-11.org wrote:
The trick is if the roller on inspection is soft to the point of goo
is to NOT INSERT a tape and foul it with the goo. I've been able to recover tapes that were
damaged by a gooey capstan
by reading the tape until a bad block appeared, cleaning the head,
and repeating.
Each pass transfers a little bit of goo from the tape to the head,
eventually removing enough to read the block.
Yes. Unfortunately, what I'm
experiencing is the roller in the cartridge
embeds itself into the gooey capstan and then stops turning. It'll start
moving fine, seeking pretty far in and then begins turning slower and
slower until it finally fails with a motor stall error.
Chris
These rollers all by now have failed to goo and
the only choice is to
remove the roller and remove the goo and replace with tygon tubing
or other rubber product. I started seeing failed rollers more than
18 years ago so this is not a new problem.
Yes. Unfortunately, they became soft
after some use. I did not have
a reference for how hard they should be when new and so they seemed OK
(a lot better than the disintegrated ones that were on the transports
when I started). I have correct diameter (5/8"OD, 7/16"ID)
tygon tubing as well as
various types of o-rings on order that I will try as replacements.
I am guessing about the durometer of the rubber so have a selection of
different hardnesses to try and see what works.
Since there was no new build back 18 years ago I went to a repair
solution and have use it since. Mins was specifically a .150-.160
wide ring of tygon of the right ID to fit tight on the cleaned hub
and anchored with a drop of superglue. I tried Orings and they
were hard to find with the right ID/OD and it required machining
the hub to have a grove to keep it.
Since the tape has servo data for speed (part of the encoding)
the OD of the roller can vary with no ill effects so long as mechanical
fit and traction are good.
Allison