[BC] unreliable old equipment query

[Xen Scott]

At 01:55 PM 12/27/2011 -0500, Donna Halper wrote:
>... Everyone who was working in TV at the time recalls how temperamental 
>and unreliable the electronics were, but exactly how temperamental and 
>unreliable
>is not spelled out.  So I am trying to find comprehensive and detailed
>information about the extent of it:  what were the most common component
>failures that would lead to loss of service (not necessarily loss of the
>signal altogether, which was quite rare.)  Essentially anything that led
>to the "We Are Experiencing Technical Difficulties" slide appearing fits
>the definition, with the exception of component failure from external
>causes.... What were the most common components to fail, how long on average
>would it take to fix them...

My experience beginning in the 1960's is that the most common cause for 
failures were things mechanical, like switches, motors and related items, 
connectors and
physical splices in film and videotape.  The next most likely component caused
failure would be anything that got hot in normal operation such as tubes,
projection lamps and studio lights.

My experience was that if good preventative maintenance was done, that went
a long way toward improving the reliability of equipment.

Another factor was the design of the equipment.  Certain brands of broadcast
equipment had known compromises as a cost-savings consideration and therefore,
by design, were less reliable and temperamental.  If a piece of electronics 
uses components sized to be just adequate for the task, the probability of 
failure is
much higher that it would be if the device in question had components with some
reserve capability.  Using a five watt resistor to dissipate 4.9 watts is 
asking
for failure.

An example from my experience is the RCA BTA-5T 5kw AM transmitter.  The 
design
of the final amplifier stage required that several tuning variables be kept in
precise adjustment or the life of the final amplifier tube would be cut 
drastically
short and failure would result.  Other components in this transmitter were also
undersized so that certain kinds of audio would cause the transmitter to 
overload
and shut down.

As for how long it would take to fix the problem, that depends on the how fast
the problem could be identified, how difficult it was to get to the failed
component and whether the replacement part was on hand.  At the broadcast
facilities I worked at, the first move would be to find a work-around to the
failed device.  Sometimes it was as quick and simple as throwing a switch or
inserting a patch cord.  In the case of film or videotape, moving to another
film projector or videotape machine was usually the quickest means of getting
back on the air.  Monitors were usually swapped out with a shelf spare as were
things like distribution amplifiers and audio tape machines.  The speed of 
recovery
all depended upon the resources of the broadcast facility.

Xen Scott