CCE HPS-2971 - Fly Back Transformer Auxiliary Supply; High Voltage (EHT) Measurement

HPS-2971
3.2.4 Auxiliary power supply from Fly Back Transformer.
a) Connect the TV under test to a 117 Vac/60 Hz line.
b) Turn on the TV and apply a 60dBmV signal (frequency and channel defined
by factory) 88% modulated with white pattern and audio signal with 400Hz
frequency modulated in FM with ± 25kHz of deviation.
c) Adjust the TV to a “PP” condition.
d) Utilizing a electronic DC voltmeter (over 10 M input impedance), read the
auxiliary power supply from Fly-Back transformer.
e) Read the RMS voltage apply to the CRT heat. Utilizing a true RMS
voltmeter.
f) When exist, read the auxiliary wind Peak to peak voltage, utilizing an
oscilloscope.
Conition Test Point Minimum Nominal
Maximum
Unit
“PP” 117V
AC
+13,00V (Cathode of D410) 11,90 12,70 13,50 V
DC
“PP” 117V
AC
-12,00V (Anode of D407) -13,00 -12,50 -12,00 V
DC
“PP” 117V
AC
210V (Cathode of D408) 190,00 208,00 215,00 V
DC
“PP” 117V
AC
CPT HEATER (Pin 3 of CN401)
5,70 6,30 6,90 V
RMS
3.2.5 High Voltage (EHT)
a) Connect a DC voltmeter to the resistor wired to the Fly Back ABL pin (the
position and value of this resist is defined by each model.
b) Connect a high voltage electronic DC voltmeter (over 1G impedance) in the
electronic tube high voltage plug.
c) Adjust the bright, color and contrast controls to minimum and read the high
voltage E.H.T. (@ I
A
min).
d) Adjusting the bright control to the maximum position, contrast control to the
maximum position and monitoring the voltage through the ABL resistor
(RABL), adjust the bright control until the DCVABL voltage reached the
specific value. The anode electric current will now be define by the following
equation:
I
A
=(V
ABL
/R
ABL
)
Read the high voltage E.H.T. in this conditions (I
A
max.).
Condition Minimum Nominal Maximum Unit
I
a
min. 28,50 30,50 32,50 kV
DC
I
a
=1,70mA 26,50 28,50 30,50 kV
DC