17 Feb
2008
17 Feb
'08
12:58 p.m.
djg at pdp8.net wrote:
I am working on restoring a DEC TU10 tape drive for my
PDP-8/E and want to
see if anybody has experience repairing them before I do too much to it.
It was made in 1973 and probably last powered up in 1988. I have the
maintenance manuals and prints for it. Though for some reason they don't
have the 20 year idle maintenance procedure.
Does anybody have a TU10 with a good capstan who can accurately measure
the diameter or the coating thickness?
Also does anybody have a 9 track 800 BPI alignment/skew tape? A bunch
of the maintenance procedures use it.
So far I have cleaned it and taken stock of its condition.
The vacuum switches are bad but it looks like they are still made
by World Magnetics so I should be able to get new. The markings on them
don't exactly match the new parts so hopefully the manual 10" H2O
is correct. If anybody knows more it would be appreciated.
The capstan is past dead and seriously into decomposing. The price for a
NOS one is scary. It is about 1.8" in diameter and directly moves the
tape. Since this is a critical component to the tape path I suspect my skills
with the do it yourself repairs will leave it too lopsided. Has anybody
tried www.terrysrubberrollers.com. I saw a couple references on the list but
didn't see any reports of results. It looks like he uses some black rubber
which I don't know if it will have similar friction to the original.
I measured 3 of mine and there all over place. My TE-16 is the best
and it has a OD of 1.825
the next one (TE-10) 1.840 . Both of these have black rubber type of
friction material. The 3 rd
one is going bad and is at 1.840. This has a tan colored friction
material and may be swollen.
I have worked on mine a lot and keeping them going is some times
trying. I have found that finding
all of the problems takes a while. Mostly the adjustments change in
time so by now most will be off.
Start with cleaning the connection everywhere. If it then turns on
with out the reels spinning
let it run for a while with out any tape. Then try the adjustments.
Always write down which
adjustments where off and how far. This helps later when it all of a
sudden it eats a tape and you
need to go back and see what changed.
To test the loading part of the system. I use a short piece of tape
through the vacuum column,
anchored at one end. Then I position the tape in the columns close tho
where it has been running
in the past and hit load. (no tape on the spools) Then just move the
tape in the columns to see
what the motors will do. This also lets you run the motors to help with
the brakes or dry grease.
These drives can be very brutal on a good tape so go slowly. One always
ends up with a shorter
tape no mater how hard you try.
I don't have the alignment tape.
- Jerry
Jerry Wright
g-wright at att.net
From whats left it looks like the original capstan
was translucent amber.
The blower sound noisy when turned by hand. Plan to see
if I can
open and inspect.
One of the reels doesn't turn easily. The manual has a section on
cleaning the brakes so plan to do that.
Plan to do the standard power supply checkout.
A lot of the old equipment like this tape drive has parts with permanently
lubricated ball bearings. So far I have decides that if the device sounds
fine to leave them alone since it won't get that much use and taking it
apart enough to get the bearings out has some risk. They also are sometimes
pretty well sealed making cleaning and relubricated difficult. I have
wondered how good 20-30 year old grease can be. What do other people do?
Has anybody found a good way to relubricate these type of bearings to
prolong the life? Or wait until they fail and hope the bearing assembly
matches something you can buy?
Thanks,
David Gesswein
http://www.pdp8online.com/ -- Run an old computer with blinkenlights