Qls 14N23, Service Manual

Page: 12 / 54

TCL-THOMSON Electronics R&D Center (Shen’Zhen Lab)
Chassis Name
M123SP
南美软件
Serial No.
Issued on
2006-04-29
Page
6 of 13
Updated on
2006-07-29
Version
2.0
Ⅱ
. Alignment contents
：
1. Adjustment of B+ voltage
Receive Philips standard testing pattern to RF input.
If the VR800 exists in the board, adjust it in STANDARD mode until voltage at following
value ：
Model B+ (v)
M123SP 110
± 2.0
21E10
110
±
2.0
2. RF AGC adjustment
AGC Alignment Procedures:
1)
Apply 8-scale gray signal (80dB), then adjust AGC data in D-mode to get the noise
picture ( snow picture) disappear exactly. Test Pin 1 of TU101 (IF output) and
record the voltage value as V1
P-P.
<Illustrate as Picture A>
2) Apply 8-scale gray signal (80dB), and then adjust AGC data in D-mode until the
synchronization signal distortion appear exactly. Test Pin 1 of TU101 (IF output)
and record the voltage value as V2
P-P.
<Illustrate as Picture A>
3) Calculate the value of V
P-P
with the formula: V
P-P
＝ (V2
P-P
×V1
P-P
)
1/2
Apply 8-scale gray signal (80dB), test Pin 1 of TU101 (IF output), adjust AGC data
until the voltage of Pin 1 of TU101 V
P-P
＝ (V2
P-P
×V1
P-P
)
1/2
。
4) Test three units according to 1)
，
2)
，
3) steps, and record the values of AGC in three
units. Take the average value as benchmark.
Remarks:
Comparing test is necessary due to different probe of Oscilloscope and different Test
Circuit (Picture A).
1)
AGC voltage value should be tested afresh, due to the type/supplier of Tuner
or Saw filter changed, or other related components changed.
IN60
3P f
output
input
100K IN60
(Picture A)
12