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SLEEP CRT



		CRT STANDBY ( SLEEP CONDITIONS)

Many telecine users ask what is the preferred mode for the telecine crt when the
machine is not in use. Customers over the years have used several options but as
crt`s and telecines have changed here are Brimar`s latest suggestions.

URSA TELECINE If the standby period is lengthy i.e. overnight/weekends/holidays
then switch off the crt including the heaters. When powering up again leave the
raster on , zoomed out and de-focussed for an hour. This is plenty long enough
to stabilise the cathode and screen and the crt can now be set up for normal
operation.
If the standby period is short i.e. just a few hours then from the programmer
zoom out the raster  ensuring that the raster is not over the edge of the
faceplate but is larger than any gate option. De-focus the raster and leave at
the normal operating beam current.

MKIII TELECINE If the standby period is long then from the local  panel zoom out
the raster  ensuring that the raster is not over the edge of the faceplate.but
is larger than any gate option de-focus the raster using the fine focus control
on the focus P.C.B. Leave the beam at the normal operating current.
If the standby period is short then leave the crt set-up for normal operation.

TURBO II TELECINE This telecine has it`s own clever crt management system and
the E.H.T. and heaters can be ramped off if the standby period is long.If the
standby period is short leave set for normal operation.

GENERAL Brimar crt`s are designed to run at  4Volts  and the voltage should be
checked periodically and definitely when fitting a new tube. Running heaters too
hot evaporates away the Barium and Barium Oxide, depleting the cathode rapidly
and fusing the crystals. The result is a loss of emissivity and short life
emission failure. Running too cool restricts the Barium creation/diffusion
mechanism to a rate that cannot support the necessary Barium concentration at
the surface, this leads to depletion and emission failure.  
Some customers use the focus rock facility as a standby or burn-in mode, Brimar
do not recommend this practice. Activating the focus rock applies an A.C. square
wave to the main focus current and if the crt is only slightly de-focussed this
square wave could drive the crt back into focus every half cycle.
Running a crt without E.H.T.or very low beam is also not advisable.
There is no evidence to support the theory that  reducing the beam current
during standby periods increases life.Tests we at Brimar have done and feedback
from customers supports  the opposite in that the crt is happier with the beam
left set. 
What is absolutely certain of course is that more front-end light gives better
signal to noise through the telecine.  
Anyone with queries on the above or tubes in general should contact David Hurst
RCInc Valencia if residing in the USA/ CANADA or contact me at Rank Brimar if
located in the rest of the world.

Regards
Eddie