Sharp 21F-PA18, Service Manual

Page: 60 / 89

21F-PD250 / 21F-PT220 / 21F-PA18 / 21F-PA18(B)
5 – 1
TV 21Q-FG1F Service Manual 21Q-FG1F Market E CHAPTER 5.
TROUBLE SHOOTING FLOWCHART
[1] TROUBLE SHOOTING FLOWCHART
NO RASTER
Blown out.
Replace the fuse.
Check IC701, D701 and
C705.
The fuse is blown out again.
Does horizontal circuit
oscillate ?
Check T702 pin (17) voltage
(Approx. 310V at 220V AC)
Check F701.
Check Secondary Main+B
(Approx. 125V)
Check CRT connector K-
wire and the signal on it.
Check Q601 and Q602.
Check 185V
Bias on
CRT board.
Check
IC801.
Checking the
protector circuit.
Check Q752 for 8V regulator
circuit and Q753, IC751, Q754
for 5V regulator circuit.
Check D751.
Check NR701.
NO PICTURE, NO SOUND
No snow noise.
Does noise or signal appear at pin (24)
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 (36) at
IC801 and related
circuit.
Check pin (37) of
IC801, Tuner and
related circuit.
Check pin(24) 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.
Does noise or
signal appear at
pin (38) and (39)
of IC801 ?