13
AK - 44
CHASSIS
9.1 B.C.L Circuit (Beam Current Limiter)
Beam current limiting is employed to protect the circuitry in the receiver, the CRT and to prevent excessive X Ray
radiation in fault conditions. The current drawn by the CRT is monitored by the current drawn through the winding of the
fly-back transformer that produces the EHT for the CRT anode. The end of the winding (Pin 10) is returned to IC403
Pins 46, the beam current drawn by the CRT passes through Q603 and develops a voltage on the collector proportional
to the current (V=IxR).
The voltage on the collector will vary depending on the beam current being drawn reducing the brightness and contrast
of the picture. If the voltage is sufficiently negative (indicating very high excess beam current) the output will be re-
duced, reducing the picture brightness and contrast.
10. SERIAL ACCESS CMOS 8K EEPROM 24C08
The 24C08 is a 8 Kbit electrically erasable programmable memory (EEPROM), organized as 4 blocks of 256*08 bits.
The memory is compatible with the I²C standard, two wire serial interface which uses a bi-directional data bus and serial
clock.
EEPROM Initialisation
If the E²PROM IC500 is replaced it will come fully programmed and therefore it is not necessary to initialise the new
device. In some circumstances the E²PROM may become corrupted in use i.e. static discharge or lightning strike. If this
happens, it is advised that the E²PROM is replaced.
11. SAW FILTERS
Saw filter type: Model:
G1975M:
PAL B/G MONO
K2966M:
PAL SECAM B/G/D/K/I MONO
J1981 :
PAL-I MONO
K2958M:
PAL-SECAM B/G-D/K (38) MONO
2962M:
PAL-SECAM B/G/D/K/I/L/L’ MONO
L9653M:
SECAM L/L’ AM MONO (AUDIO IF)
G3967M:
PAL-SECAM B/G STEREO (VIDEO IF)
G9353M:
PAL-SECAM B/G STEREO (AUDIO IF)
K3958M:
PAL-SECAM B/G/D/K/I/L/L’ STEREO (VIDEO IF)
K9356M:
PAL-SECAM B/G/D/K/I STEREO (AUDIO IF)
K9656M:
PAL-SECAM B/G/D/K/I/L/L’ STEREO (AUDIO IF)
K3958M:
PAL I NICAM (VIDEO IF)
K9356M:
PAL I NICAM (AUDIO IF)
12. IC DESCRIPTIONS AND INTERNAL BLOCK DIAGRAM
ST92195
STV224X
TUNER (UV1315, UV1316, UV1336)
TDA7266L / TDA7266M
TDA8174A
TDA6107
MC44608
MSP34X0G
24C08
TDA1308
SAW FILTERS
G1975M, K2966M, K2962M, L9653M, G3962M, G9353M, K3958M, K9356M, K9656M, K6263K, K9652M
Summary of Contents for 21LF-90N
Page 6: ...6 21LF 90N CHASSIS LAYOUT Mother Unit CRT Unit Headphone Unit ...
Page 48: ...36 AK 44 CHASSIS 1 I H G F E D C B A 2 3 4 5 6 7 18 4 Schematic Diagram of Audio Circuit ...
Page 52: ...40 AK 44 CHASSIS 1 I H G F E D C B A 2 3 4 5 6 7 18 7 Schematic Diagram of CRT Socket Circuit ...
Page 55: ...43 AK 44 CHASSIS Notes ...
