[BC] unreliable old equipment query

[Ron Youvan]

   Donna Halper wrote:

> I am posting this message to several lists, in hopes of getting some
> information.  My Canadian friend Art, who is writing a book with a
> backdrop in late 1940s or early 1950s broadcasting, asked this of me,

   I can tell you from my experience at an educational TV station that was populated with old used 
"hand me down" equipment that a film breaking (separating at a splice actually) was most likely one 
of the most common causes of a test slide.
   Two projectors allowed switching from film to film, but a projector problem would make it 
necessary to sit on a slide {usually an ID slide} until one film could be removed and the next threaded.
   For a network connected station a failure of the "local loop" the cable (with regularly spaced 
amplifiers) or microwave link from the TELCO connection or the hilltop to hilltop AT&T 4 Gig 
microwave links failing, which would require dispatching to one of many un-manned repeater sites. 
(every 40 miles of so)  (the network signal could be changed to an unused channel if a main unit did 
not fail, they carried 4 channels per link)
   Transmitter wise (no trouble slide would be possible unless it effected only the aural 
transmitter) the earliest transmitters were water cooled, some with 6,000 Volts across a 2" piece of 
plastic tubing made of "saran" plastic (like saran wrap) that physically deteriorated in months and 
if not "caught" during daily inspections would split ever so slightly and spray a mist of distilled 
water on the RF chokes and other components, if it just dripped it would kill drive until it 
evaporated (5 to 20 seconds) then it would repeat when the next drop landed until the transmitter 
was shut down and the water cooling link was replaced, perhaps a 1/2 hour job including warming up 
the filaments again before the high Voltages could be reapplied and broadcasting could resume.

   When I started (8-63) the studio had one known transistor in one piece of equipment, the 
transmitter none, everything else was tube operated.  Critical equipment was installed with a backup 
unit like the MW transmitters and receivers as a rule.  As soon as a failure was understood, the 
alternate equipment would be pressed into service.
   Much time was spent testing tubes and recording the values from the tube tester into log books, 
and the supervisor decided when a tube was approaching it's end of life before it failed while in 
use if the tester did not change it at the time of testing.

   Equipment like "sync generators" were initially installed signally and when everything in the 
building started rolling, adjustments were quickly made, if that didn't help then tubes would be 
gotten from the maintenance shop and some "shot-gunning" would take place.

>          and what percentage of the broadcast hours would the average
> station expect to lose over the course of a month?"  Any guidance you
> can offer will be appreciated!

   Normally not one hour monthly from internal causes.  Perhaps 4 to 8 annually which depends on how 
fast repair parts could be acquired.  (overnighted from the factory)

-- 
Ron KA4INM