Test Mode - Sony ICF-SC1 Service Manual

Reading the S-Curve voltage for scan-stop
The ICF-SC1 and SC1PC have a scan-stop function used to scan
for the correct frequency.
Scanning continues until the squelch turns off (when a signal is
received). However, just setting the squelch off as condition does
not guarantee that the scan-stop function will always stop at the
correct frequency. (It might for instance deviate 1 step to an adja-
cent frequency.)
So scan-stop is set to trigger only at the correct frequency, by check-
ing the DC voltage component (S-curve voltage) of the FM detec-
tor output.
The DC voltage component of the FM detector output may vary
however, due to variations in the parts components of the FM de-
tector circuit or deviations in the local oscillator frequency. There-
fore, once repair or alignment is complete, read the DC voltage
component of the RF detector output while it is input with an IF
signal from a signal generator, and use that value as a reference to
write data on the EEPROM.
Two types of writing are performed on the EEPROM since there
are two types of FM detectors.
WFM n for WFM
NFM n for NFM, AM
Refer to the following for information on the write method and on
the signal input method using a signal generator.
LCD (all lamps on)
All LCD lamps up when the three [EXE], [–] and [SCAN] keys are
simultaneously held down while the power is off.
Reading the S-Curve voltage component
1. Input method for S-Curve voltage component read mode
Simultaneously hold down the [MODE], [STEP] and [BAND] keys
for at least 1second while power is off.
The set (ICF-SC1/SC1PC) power turns on and a display as shown
below appears.
2. Quitting S-Curve voltage read mode
Press the [POWER] button.
When set in S-Curve voltage read mode, do not connect any-
Note :
thing to the antenna terminal while the power to the RF sec-
tion is on. (An unwanted signal might otherwise be received
through the antenna.)
However when set, a check can be made that a broadcast RF carrier
wave was received.
(1) Turn the power on as usual and receive a broadcast signal.
(2) Turn off the power and set in read mode with [MODE] + [STEP]
+ [BAND].
(3) Write can be checked with [SVC] or [SCAN] since the broad
cast signal received in (1) can be heard.
In the following cases the message "TRY AGAIN" appears and
writing is disabled.
(1) When the Squelch is closed.
(2) When the S-curve voltage that was read, is not within 0.5V to
1.3V.
SECTION 3

TEST MODE

S-Curve voltage write method
Signal input method using signal generator.
1. In NFM
(1) Connect a signal generator to TP1 by way of a 0.01µF capaci-
tor.
(2) Receive NFM (Receive frequency does no matter)
(3) Input 455kHz from the signal generator, 90 to 100dBµ, modu-
lation 30%, mod frequency of 1kHz.
(4) Write the COMPN terminal voltage onto the ROM.
(5) Press the [SVC] button.
When data is written, a display as shown below appears.
2. In WFM
(1) Connect a signal generator to TP4 by way of a 0.01µF capaci-
tor.
(2) Receive WFM (Receive frequency does no matter)
(3) Input 10.7MHz from the signal generator, 90 to 100dBµ, fre-
quency deviation 22.5kHz, mod frequency of 1kHz.
(4) Write the COMPW terminal voltage onto the ROM.
(5) Press the [SCAN] button.
When data is written, a display as shown below appears.
Adjustment Location :
[ IF BOARD] (Rear side)
– 12 –
TP1
C407
1000P
MIX
16
IN
0.01µ
IC401
S.G.
TA31136FN
0 . 9 4
NFM
Voltage (V)
TP4
C434
0.01µ
FM RF
10
IN
0.01µ
IC402 S.G.
CXA1111N
WFM
0 . 8 7
Voltage (V)
CN402
45M X'tal filter
RF BOARD
COMPN
COMPW