31 Mar
1997
31 Mar
'97
5:16 p.m.
At 06:01 PM 3/31/97 -0800, you wrote:
I was talking to a friend this weekend who brought
up this idea that before long EPROMs in our old
computers are going to start to go bad. This is
something I've heard before but, to be honest, I
don't know enough to make a judgement on it. If
this is the case, I suppose I should be burning
backups.
While I'm at it... What are some other concerns
along these lines. What should we be planning
for as these machines grow 5, 10, 15 years older?
Good questions all, so some comments and some thoughts.
EPROMS: yes, they will forget. Being stored charge devices they will
eventually start to lose the stored information. As I recall the original
estimated life for stored data was 10-15 years. Punched tape (mylar
preferably or paper if stored properly) may be the closest thing we have to
a true "archival" medium.
Electrolytic Capacitors: They dry out, or will start to ooze the
electrolyte. (I address this to some extent on the 'Repair Tips & Tricks'
section on my web pages) Average lifetime (of large caps such as found in
power supplies) is probably 5-10 years. On machines that I restore they
are (almost) always replaced before I do anything else. The very small
caps found on logic boards for timing and similar circuits do not seem to
be a prone to failure.
Disks: depends highly on how they are stored. Should be treated similar
to records. (remember those?) Store upright, loosely packed, dry but cool.
Watch for oxide flaking on very old disks.
Tapes: similar to disks for storage. Should be retensioned (repacked?)
from time to time. (fast forward to end, then rewind)
As with disks,
watch for oxide flaking. Dampness will cause some tapes to adhere
to
itself, and strip off the oxide when run. Had this happen to my "Standard
Pack" tape for an HP-85 I obtained recently. Went to load the tape and got
a read error. Manual inspection of the tape showed a 3/4 inch strip where
there was no oxide at all. it was stripped away by the tape adhesion when
I rewound the tape for probably the first time in 4-5 years!
Card edge connectors: corrosion is common, expecially is stored in damp
places or contaminated by skin oils. Can be cleaned with the classic "Pink
Pearl" eraser. (Don't use the grey erasers - too abrasive!)
Hmmm... probably more, but it's late and I forget... (often it seems - bad
EPROM?)
More later...
-jim
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jimw(a)agora.rdrop.com
The Computer Garage - http://www.rdrop.com/~jimw
Computer Garage Fax - (503) 646-0174