Sharp 21YF30, Service Manual

Page: 30 / 60

21YF30
30
TROUBLE SHOOTING TABLE
NO RASTER
Blown out.
Replace the fuse.
Check IC701, D701 and
C705.
The fuse is blown out again.
Does horizontal circuit
oscillate ?
Check T701 pin (17) voltage
(Approx. 310V at 220V AC)
Check F701.
Check Secondary Main+B
(Approx. 130V)
Check CRT connector K-
wire and the signal on it.
Check Q601 and Q602.
Check 190V
Bias on
CRT board.
Check
IC801.
Checking the
protector circuit.
Check Q752 for 8V regulator
circuit and Q751, Q752 for
5V regulator circuit. Check D751, IC702, D750
and IC703.
Check R701and R730.
TROUBLE SHOOTING TABLE
(Continued)
NO PICTURE, NO SOUND
Does signal appear at pins
(10) and (21) of IC3501 ?
NO SOUND
No snow noise.
Does noise or signal appear at pin (41)
and (58) of IC801 ?
Noise increases but no signal is
received.
Check the tuner supply voltage LB must
approx. 5V. BT must be approx. 33V.
And check the CH preset data.
Check the tuner AGC at
TP201.
Check IC801 and
related circuit.
Check pin (1) of
SF201, Tuner and
related circuit.
Check pin (60) at
IC801 and related
circuit.
Check pin (59) of
IC801, Tuner and
related circuit.
Check pin(58) of
IC801.
Does the noise level increase at max.
Contrast, Brightness and Sound controls ?
CIRCUITS TO BE CHECKED:
»
Tuner.
»
PIF.
»
Automatic Gain Control.
»
(5V), (32V) Power Source.
CIRCUITS TO BE CHECKED:
»
Sound Detector Circuit.
»
Sound Switch and Att.
Control.
»
Audio Output Circuit.
Does signal appear at pins
(6) and (8) of IC301 ?
Check TV sound from pin (54)
of IC801.
Check Speaker.
Does noise or
signal appear at
pin (63) and (64)
of IC801 ?
Check IC301 and
peripheral circuit.