local demolition of SAGE building

Mike Loewen mloewen at cpumagic.scol.pa.us
Tue Jul 19 15:23:21 CDT 2005

On Tue, 19 Jul 2005, Teo Zenios wrote:

> How many vacuum tubes would need to be replaced yearly, and how would a few
> breaking affect the functioning of that equipment in real time?

    I don't have the figures for annual tube replacement, but it was a 
continuous process.  As I mentioned in my last note, the marginal checking 
system allowed us to pull suspected flaky or about-to-fail tubes before 
they failed on duty.

    Various SAGE histories have reported "technicians running up and down 
the aisles pushing shopping carts full of tubes".  I don't know about 
other air divisions, but I never saw it.

    Towards the end of the system's life, the remaining SAGE systems had to 
make due with tubes scrounged from previously deactivated systems. 
According to others who worked on the system, sometimes the replacements 
were worse than the ones currently in use.

    The SAGE system actually had two computerss: one running the air 
defense program and the other usually on standby.  When the standby system 
wasn't undergoing preventive maintenance (PM), it would be receiving 
updates from the active system in case it needed to take over.  If the 
standby system sensed that the active computer was no longer functioning 
correctly, it would automatically switch over and start cycling the air 
defense program.  If something happened that the standby didn't 
automatically switch in case of a failure, we'd have to do a manual 
switchover.  Depending on the circumstances, this procedure could take up 
to 3 minutes, which is all the down time we were allowed before having to 
report a "noplex" condition to NORAD.

Mike Loewen				mloewen at cpumagic.scol.pa.us
Old Technology	http://ripsaw.cac.psu.edu/~mloewen/Oldtech/

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