Hitachi 61HDX98B Manual page 102

DEFLECTION TROUBLESHOOTING (Deflection and High Voltage Drive Signals)
The deflection circuit in the DP-85 chassis operates
differently from previous chassis. This chassis utilizes
a duel horizontal section. One
for High voltage and one for de-
flection. The High voltage sec-
tion will not operate without the
deflection section operating.
The deflection section receives
it's drive waveform from I702
on the sub deflection PWB. The
Drive signal can be checked on
PDD1 connector at Pin 7.
This drive waveform is made avail-
able to the base of Q751. The sig-
2
nal off the collector of Q751 is
routed to the Drive transformer
T751, which in turn supplies a sig-
nal to the base of the Deflection
Horizontal Output Q777.
Q751 Base
3
Investigate
these wave-
forms care-
fully.
Q751 Collector
When the deflection circuit fires
up, it produces drive for the
Horizontal Deflection Yokes, as
well as several other different
signals.
One of the Waveforms produced
Q755
6
Base
PDD1 Pin 7 (H. Drive)
Q777 Base
5
Q777 Collector,
And T752 Pin 1
is Horizontal Blanking. This
is created by Q755.
The signal off the Collector
of Q777 and/or Pin 1 of
T752 is routed to the Base of
Q755.
Q755 functions as an Emitter
follower and produces the
Horizontal Blanking signal
from it's Emitter.
1
Another signal produced is
utilized by the Conver-
T752
Pin 10
8
into the IC or rectified outside the IC to become -33V.
Likewise, the 28Volt
power supply is proc-
essed the same way.
4
The Deflection H. Pulse
T752
Pin 7
Deflection
H. Pulse
10
lector of Q777 and/or
Pin 1 of T752 is routed
to IH01 pin 1. This IC is
responsible for Wave-
shaping and delaying the
signal to be utilized by
the High Voltage Sec-
tion.
After entering the IC, it is output at Pin 4
IH01
Pin 4
12
Q755
Emitter
Also
H.Blk
7
gence section. The nega-
tive 28Volts from the
Power supply is sent
through T752 and a Pulse
is added to it. This in turn
is routed to the Conver-
gence output Transistors
and is either sent directly
T752
Pin 11
9
is produced from T752 pin
7. This signal is used to
detect for proper operation
of the Deflection circuit
through Q754 and Dy-
namic Focus by DF02,
QF02 through QF09.
The output from the Col-
IH01
Pin 1
11
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