Sony D98 chassis Operation Manual page 3

CN600
1. AC Input Section
The AC input section provides EMI filtering, input protection, surge limiting and CRT degauss operation. An AC switch is
also present for complete power off condition.
EMI Filter
The EMI filter comprises X-capacitors C601 and C602, Y-capacitors C603, C604, C605 and C606 and the line filter
transformer, LF602. Input protection is provided by F601 and surge current limiting by thermistor TH600 and resistors
R602 and R603. Degauss is explained in the next section.
The front panel AC switch is wired electrically between R602 and TH600 and when closed, completes the circuit. This
allows the bridge diode, D601, to full wave rectify the AC input voltage.
Degauss Circuit
The degauss circuit is used to demagnetize the CRT. After power on, the microprocessor located on the N Board sets the
degauss signal to digital high and through Q607 turns on relay RY601. This allows AC current into the degaussing coil
through posistor THP602. The current heats up the posistor and its affective resistance increases, this dampens the current
in the degauss coil to nearly zero. Duration time is approximately 5-6 seconds and the microprocessor then shuts off
RY601, which disconnects the degauss coil from the AC line. This operation should sufficiently demagnetize the CRT.
2. Primary Circuitry Section
IC601
The heart of the primary section is the AN8037 power supply controller, IC601. The following describes the functions of each
pin.
Pin 1 – TR - This is TR or transformer reset. Similar to a demagnetization function, this pin detects the falling edge of the
primary waveform during relaxation period. It allows the next conduction pulse only after reaching the bottom of the ringing
waveform. It contributes to the maximum on time setting.
AC input and Degauss
F601
4A
250V
LF602
C602
C605
C601
C606
R601
-
3
CN601
THP602
12V
VR601
RY601
R672
D601
C604
C603
TH600
R602
AC SWITCH
-
D670
Q670
R670
R671
R603
0.68
10W