Tube replacements in old computers 
Author Message
 Tube replacements in old computers

I understand the popular IBM 650 computer as well as the card
calculators used vacuum tubes.  How long did these tubes last until
burnout?  If a tube died, did the machine crash with it?  Were dead
tubes hard to find?
Thanks.


Wed, 14 Jan 1998 03:00:00 GMT  
 Tube replacements in old computers
I came on the scene just after tubes.  IBM's  SMS technology, which was
discrete transistors.  However, I do recall swapping stories with some of
the 'old timers' of that day.  The tubes in question were really just
used as digital switches.  Nothing {*filter*} like the analog in a radio or
television :).  I understand the most prevalent failure mode was that
the filaments in the tubes would burn out.  According to stories I have
heard, you could find the bad tube by simply turning off the lights and
looking for the tube that wasn't glowing.  I believe this was also done
as a form of preventitive maintenance.

Regards,
Terry Kummell



: calculators used vacuum tubes.  How long did these tubes last until
: burnout?  If a tube died, did the machine crash with it?  Were dead
: tubes hard to find?
: Thanks.
--

Running MVS, VM and VSE on a Pentium 90 under Linux and Unixware!



Thu, 15 Jan 1998 03:00:00 GMT  
 Tube replacements in old computers

Quote:

>I understand the popular IBM 650 computer as well as the card
>calculators used vacuum tubes.  How long did these tubes last until
>burnout?  If a tube died, did the machine crash with it?  Were dead
>tubes hard to find?
>Thanks.

   Tubes worked because the cathode was at a temperature that allowed the
electrons to "boil off" into the area where the grid, etc, were located.
When the tube "burned out" it was generally an open filiment circuit. The
experimental tube-type computer circuits that I was told about kept an
incandescent light bulb in parallel with the filiment. When that was open
current would flow through the bulb, lighting it - so when a light came on,
you replaced the tube next to it! (Burned out light bulbs, however, were a
different problem altogether :-)

Regards,

Alex Vrenios, kx9i

Arizona State



Fri, 16 Jan 1998 03:00:00 GMT  
 Tube replacements in old computers

Quote:
>I understand the popular IBM 650 computer as well as the card
>calculators used vacuum tubes.  How long did these tubes last until
>burnout?  If a tube died, did the machine crash with it?  Were dead
>tubes hard to find?

I have no idea what the life span of an individual tube was, but I understand
it was quite easy to find most bad ones.  Since it was usually a burned out
filament, you just turned out the lights and looked for the dark one.


Sat, 17 Jan 1998 03:00:00 GMT  
 
 [ 4 post ] 

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