Abgleichvorschriften / Adjustment Procedures
Challenge 600 A CD SR
4
GRUNDIG Service
k
Adjustment Procedures
Test equipment: DC Voltmeter, Test Generator, AF Voltmeter, Stereo Coder, Distortion meter
After repairing the RF or IF Part the adjustment of Signal Level Offset (para 8) must be done.
1. Oscillator (AM and
FM)
2. AM IF
3. FM Pre Stage
4. FM Band Pass
5. FM IF
6. FM Demodulator
7. Sliding Stereo
Mono Transition
8. Signal Level Offset
Adjustment
Preparation
Adjustment Procedure
FM;
Connect a DC Voltmeter to FMP16.
Connect a Test Generator to aerial input; LW; Frequency
153 kHz; no modulation; E´ = 50
µ
V (34dB
µ
V).
Connect a DC Voltmeter to FMP108.
Connect a Test Generator to aerial input; Frequency
88.0MHz; no modulation; E´ = 3
µ
V (10dB
µ
V).
Connect a DC Voltmeter to FMP108.
Connect a Test Generator to aerial input; Frequency
88.0MHz; no modulation; E´ = 3
µ
V (10dB
µ
V).
Connect a DC Voltmeter to FMP108.
Connect a Test Generator to aerial input; Frequency
88.0MHz; no modulation; E´ = 3
µ
V (10dB
µ
V).
Connect a DC Voltmeter to FMP108.
Connect a Test Generator to aerial input; Frequency
88.0MHz;
f
mod
= 1kHz; dev. = 22,5kHz; E´ = 2
µ
V (6dB
µ
V);
Connect an AF Voltmeter to Loudspeaker Output.
Set AF output level to < 100mW.
f
mod
= 1kHz; dev. = 75kHz; E´ = 1mV (60dB
µ
V);
Connect a Distortion meter to Loudspeaker Output.
Connect Test Generator with Stereo Coder to aerial input;
Frequency: 88.0MHz; E´ = 100
µ
V (40dB
µ
V); f
mod
: 1kHz;
dev. 22.5kHz; Pilot dev. 7.5kHz.
Connect an AF Voltmeter to Loudspeaker Output.
Connect a DC Voltmeter to FMP108.
AM: Connect a Test Generator to aerial input; Frequency
1008kHz; no modulation; E´ = 16
µ
V (24dB
µ
V);
FM: Connect a Test Generator to aerial input; Frequency
95.0MHz; no modulation; E´ = 7
µ
V (17dB
µ
V);
Calling up parameter sets:
Switch off the unit. Hold button
¢
¢
¢
¢
¢
RADIO
depressed and
switch on the unit. Release button
¢
¢
¢
¢
¢
RADIO
only after 1 peep
was heard (abt. 5 seconds).
Press button
¢
¢
¢
¢
¢
RADIO
again, until 2 peeps could be heard
(abt. 7 seconds).
Press button
¢
¢
¢
¢
¢
TP
until 1 peep could be heard (abt. 1
second).
AM: With buttons
r
TUNING
t
select parameter 00:
e.g.
00 1700
. Note the value U
AM
(here e.g. 1700).
FM: With buttons
r
TUNING
t
select parameter 02:
e.g.
02 1640
. Note the value U
FM
(here e.g. 1640).
Calculating the Offset Value W:
AM: U
Offs
= U
AM
- U
FS
(in millivolts)
FM: U
Offs
= U
FM
- U
FS
(in millivolts)
If U
Offs
is negativ: W = 256 + (see example 1);
if U
Offs
is positiv: W = (see example 2).
U
Offs
20
U
Offs
20
Align alternating with L06 at 87.5MHz for 2.0V
±
20mV and
with C29 at 108MHz for 6.0V
±
100mV.
Align with F603A for maximum Voltage.
Align with L02 for maximum Voltage.
Align with L04 for maximum Voltage.
Align with F101 for maximum Voltage.
Align with F106 for maximum AF Voltage.
Align with F106 for minimum distortion.
Modulate left channel and adjust with R206 for 6dB cross-
talk attenuation in the right channel.
Measure Voltage (U
FS
in millivolts) and note it.
Example 1:
U
AM
= 1700; Measured Voltage U
FS
= 1842mV;
U
Offs
= U
AM
- U
FS
= 1700 - 1842mV = -142mV.
As U
Offs
is negativ: W = 256 + = 256 +
W = 256 + (-7) = 249
Example 2:
U
FM
= 1640; Measured Voltage U
FS
= 1220mV;
U
Offs
= U
FM
- U
FS
= 1640 - 1220mV = 420mV.
As U
Offs
is positiv: W = = = 21
AM: With buttons
r
TUNING
t
select parameter 50:
e.g.
50 174
. Briefly press button
¢
¢
¢
¢
¢
TP
.
With buttons
r
TUNING
t
now set the calculated value
(e.g. W = 249:
50 249
). Briefly press button
¢
¢
¢
¢
¢
TP
again.
FM: With buttons
r
TUNING
t
select parameter 51:
e.g.
51 14
. Briefly press button
¢
¢
¢
¢
¢
TP
.
With buttons
r
TUNING
t
now set the calculated value
(e.g. W = 21:
51 21
). Briefly press button
¢
¢
¢
¢
¢
TP
again.
U
Offs
20
-142
20
U
Offs
20
420
20
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