TCP/IP for VMS 5.4

[Allison]

>
>Subject: RE: TCP/IP for VMS 5.4
>   From: "Robert Jarratt" <robert.jarratt at ntlworld.com>
>   Date: Fri, 17 Jul 2009 20:08:34 +0100
>     To: "'General Discussion: On-Topic and Off-Topic Posts'"
> <cctalk at classiccmp.org>, <cctech at classiccmp.org>
>
>> -----Original Message-----
>> From: cctalk-bounces at classiccmp.org [mailto:cctalk-
>> bounces at classiccmp.org] On Behalf Of Allison
>> Sent: 14 July 2009 04:14
>> To: cctech at classiccmp.org; cctalk at classiccmp.org
>> Subject: RE: TCP/IP for VMS 5.4
>> 
>> >
>> >Subject: RE: TCP/IP for VMS 5.4
>> >   From: "Zane H. Healy" <healyzh at aracnet.com>
>> >   Date: Mon, 13 Jul 2009 10:46:51 -0700 (PDT)
>> >     To: "General Discussion: On-Topic and Off-Topic Posts"
>> <cctalk at classiccmp.org>
>> >
>> >
>> >
>> >On Mon, 13 Jul 2009, Robert Jarratt wrote:
>> >
>> >> You are right about the RD53s though. The one that came with the
>> machine
>> >> seemed a bit dubious to me but seemed at least to respond in some
>> way (I
>> >> could start a boot but it would never complete). Then one day it
>> just went
>> >> offline as if it is not attached at all, I wonder if this is not a
>> >> mechanical problem but an electronic one in this case? Is there
>> anything
>> >> that can be done to revive them?
>> >
>> >Most likely you've run into the sticky pads problem.  Hopefully
>> Allison
>> >answers this, as I believe she has experience reviving RD53's.  IIRC,
>> >basically you open the drive up and remove the sticky rubber pads.  I
>> really
>> >don't remember the details as I went SCSI nearly 10 years ago.
>> >
>> >Zane
>> >
>> 
>> If it spins up then back down and repeats thats a stuck head
>> positioner.
>> When the drive is powered down there is a magnetic retract and at the
>> end of travel there are bumpers that betwen heat and time get sticky.
>> The windup then down is the failure of the heads to move and find servo
>> and it fails.
>> 
>> There are two fixes, temprorary is to freeze the drive and sometimes
>> they unstick.  Me I open the drive, unstick the heads and reach in to
>> the mech and pull out the goo they stick too.  Never had a failure yet
>> and all 6 of my RD53s are salvaged this way and most were opened over
>> 10 years ago (two approaching 15!) and they are well past their MTBF
>> now.  I haven't opened any in years since I haven't found more and
>> generally RD53s are more useful to me as spares, swap or for the Qbus
>> pdp 11s I have. Other than that goo problem they were otherwise
>> reliable drives.
>> 
>
>I have opened up the drive by removing the top plate and I have not found
>quite what I expected. The heads are positioned under the platters, I
>expected that when retracted they would be to one side of the platters
>instead. The platters rotate freely but the heads so indeed seem to be stuck
>in that I cannot move the arm (at least not without applying some force), I
>am assuming that they are stuck because of the goo you mention. What I am
>not sure about is just how to unstick the heads, there does not seem to be
>much to get hold of and I am worried that applying too much force may break
>something. Once I have the heads unstuck the goo is going to be in-between
>the platters, is that right? I cannot see how to get at the goo to clean it
>up in that case.
>
>Any advice on what to do? Do I need to remove more parts, or can it be done
>just by removing the top plate?
>

Do not disassemble further the magnets in there are strong and you canoot align
the pieces.

Keeping in mind that if you do not unstick the heads the drive is junk. So if 
you break something nothing lost.  

Take a moment to do careful inspection of how this are put together.

Cleanliness, do avoid getting dust, fingerprints, dandruf, lint on the media.
Take reasonable care to not introduce loose foreign matter.  To that end cover
drive with it's cover when not actually working inside or between work sessions.

With that apply force as required to unstick them and (with media is rotating).
So not apply force to the end near the heads, that part is fragile but closer
to the pivot assembly where there is some structure.

Once you have gotten them free you need to deal with the failed polymer that 
is now goo.  In the past I've used a dental pick to remove it and I've also 
use a bit of paper that nicely adhered to it to prevent head sticking.

Basically the head return bumpers are there to soften and quiet the 
return of the heads to the rest position on power off decompose and 
get sticky. Those that have used TU58 and other cartridge tape drives 
know the "roller turned to goo" problem, same material.


Allison



>Thanks
>
>Rob