PROTECTION
AGAINST
X~RAY
RADIATION
patent
N°
91830158.4
12
D.C.
Power
Regulator
Horizontal
Oscillator
27
EHT
Generator
DESCRIPTION OF THE PROTECTION CURRENT AGAINST X-RAY.
g
....
>
a.
N
In the
chassis
MTC 900 - a special
protection
circuit
has been introduced
to
avoid
cinescope
radiation
which
can surpass
or
be at the high
limit
establi-
shed by law
which
is 0,5 mr/h in case
of
failure on
critical
components.
The
protection
circuit
has, a reference, a tension
of
200V taken by the secon-
dary
of
the
transformer
EHT and sending it, by way
of
a resistive divider,
to
the gate
cf
a SCR.
In
case
of
failure the nominal EHT tension
of
25,
5
KV
will increase
until
fi-
ring
of
SCR. Upon firing the SCR by-passes the
alimentation
to
the integra-
ted
horizontal
oscillator
circuit.
Thereby
stopping
the
oscillation
and, at
the
same time,
the
EHT generation.
In
order
to
re-establish
its
function
it is
enough
to
trouble
shoot
and
to
switch
on the set again. The
circuit
is calcu-
lated
in a way as
to
function
at a nominal EHT
of
27
KV.
In
these
conditions
with
the regulation
of
the
chassis
in the worst radiation
condition
and
within
the presence
of
any
critical
component
failure it will not
surpass the
value
of
0,15 mR.
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