Advertisement
Approximate measurement method
(To be used in service loop A).
• Place a CD on the turntable.
• Bring the player into service loop A.
• Check whether the DO signal (measuring point <57>) is
correct.
Normally, measuring point <57> should be "low". However,
in case of scratches on the CD, small "spikes" of about
100mV are visible.
• Check the HFL signal at measuring point <55>, figure Y.
Accurate measurement method
(Can only be applied with a playing device).
• Place test CD 4A (4822 397 30086) on the turntable
• Turn on the power switch and press the PLAY button.
• Select track number 10 and check measurement point <55>
The HFL pulses must be present.
• Select track number 15 and check measurement point <56>
The (NOT)DO pulses must be present.
The HFL pulses must also be present at measuring point
<55>.
• During track jumping, the HFL pulses are present on
measurement point <55>.
Sub. G. DOES THE TRACK DETECTOR WORK?
Measuring method (measuring points on the servo print,
principal diagram C).
• Place a CD on the turntable.
• Bring the device into service loop A and connect measuring
point <20> to ground. If a fixed resistor is used for
potentiometer R3315, fit a 330KΩ resistor between points
<32> and <33> and then connect point <20> to ground.
• Measure the FS signal at measurement point <36>.
The frequency variation depends on the eccentricity of the
CD.
• Check measuring point <60>
• Check measurement point <61>. This signal cannot be
triggered.
If 3363 is interrupted, no signal may be present at
measuring point <61>.
• Check the metering points <62> and <63>.
Sub. H DOES THE RADIAL CONTROL WORK PROPERLY?
Attention: The offset circuit (d-factor) and the AGC circuit (k-
factor) are correction circuits.
This means that under optimal conditions (new CD, minimal
deviations of the parts) it is possible that the player will
function properly even though there is an error in the offset or
the AGC circuits.
Measuring method (measuring points on the servo board,
principal diagram D).
a. Place a CD on the turntable.
b. Turn off the AGC circuit (k-factor) and the offset circuit (d-
factor).
Method: Disabling the AGC circuit: connect terminals 5 and 6
of IC6216 together or connect resistors 3293 and 3294
together.
Disabling the offset circuit:
• When potentiometer 3315 is used: Connect measuring point
<20> to ground.
• When resistor 3315 is a fixed resistor: Connect test point
<20> to ground and apply a resistance of 330 KΩ between
the measurement points <32> and <33>.
c. Bring the device into service loop B.
If the device now functions, check the k-factor and the d-
factor (see Annexes IV and III)
If the device does not work, continue.
d. Bring the device into service loop A and check the signal
at measuring point <21>
The AC component should be between 12Vpp, and
14Vpp, and measure symmetrically around zero volts.
If so, continue to point e.
If this is not the case, first check the following measuring
points:
<22>, <23> value should be 0.7Vpp
<24> value must be 0.2Vpp
<25> value should be 0.25Vpp
<26> value must be 20mVpp
<27>, <28> value measures 800mVpp, are.
Note: The frequency variation is highly dependent on the
eccentricity of the CD.
If the measuring points <22> to <28> are correct, check again
measuring point <21>.
If measurement point <21> is correct, continue.
e. Check measuring point <29> (= RE + 650 Hz).
The value must be 6Vpp. If this is the gift then continue.
When the mains switch is switched on, a signal of 650 Hz,
300mV must be present at measuring point <29>.
f.
Check measurement point <67>. The measuring point is
difficult to measure, although a small signal may be
present. (Amplitude is player dependent, can be between
40mVpp and 200mVpp).
• To check the output stage for the radial servo, only the
power switch must be switched on, and no CD must be on
the turntable.
• Inject on measuring points <30> and <31> respectively
a sinusoidal signal from 8Hz to10 Hz, 3Vpp. The arm then
moves back and forth.
Now radial tracking in service loop B should be possible.
• Disconnect resistors 3293 and 3294. If the original error
symptom is still present, proceed to Annex IV k-factor
check.
• Disconnect test point <20> from ground and, if necessary,
remove the 330KΩ resistor between the test points
<32> and <33> (See Note: Disabling the Offset Circuit).
If the original error symptom is still present, proceed to
Annex III: Checking the d-factor.
Sub. I. DOES THE P-BIT WORK?
Measuring method: (measuring points on the servo print,
principal scheme C).
• Bring the device into service loop B.
• After about 45 sec., just before the music starts, the P bit
(point 5 of the servo µP) should momentarily (about 2 sec.)
be "high". This can be measured with an oscilloscope that is
in the DC position DC at 2V/division.
Sub. J. DOES THE TRANSFER OF THE SUBCODE
INFORMATION FUNCTION?
Measuring method: (measuring points on the decoding board
principal scheme F.)
• Bring the device into service loop B.
• Check whether there is activity on the bus (points 2 and 3 of
the servo uP) (i.e. signal not continuously "high" or "low").
If this is not the case, check the measuring points <72>, <73>,
<74>, <75>, <95> and <96> and their relationship to each other
(Trigger the oscilloscope at measuring point <72>)
Sub. K. FUNCTIONS T1, I.E. THE POLARITY OF RE?
Measuring method: (measuring points on the servo board,
principal diagram C)
• Bring the device into service loop B.
• Measure T1 on PCB 13 of the servo µP.
A square-wave signal from 0V to 5V must be present here.
Due to the frequency variation, it is difficult to trigger from this
square voltage.
Sub. L. DOES THE DIGITAL DECODER CIRCUIT OPERATE
ACCORDING TO SPECIFICATION
Measuring method: (measuring points on the decoder board,
principal diagrams F and G.)
• The first condition is that the motor is running at a good speed.
This implies that the PLL circuit is OK.
If not, use measurement method Sub E.
• The second condition is that the HF preamplifier functions
properly. See Annex V (test method for the HF preamplifier).
• In principle, special measuring equipment is required for
servicing the digital decoding circuit, in particular for
measurements at the information outputs.
• For practical reasons, Service supplies an IC set, consisting of
specific digital ICs code number = 4822 395 30194. Based on
this set of ICs, a possibly defective IC can be located by the
method of "trial" and error''.
• In addition to the information outputs, which are in principle not
measurable with a working device, a number of communication
lines, responsible for the timing, are measurable.
In this way, faults in the periphery of the specific digital ICs can
also be localized.
These signals can be checked with a normal oscilloscope.
The following applies to information outputs
• In a locking device it can only be checked whether information
IS present or not.
• In a number of cases, measurements can be made in a non-
playing device. See the tables for this.
Measurements
DEMOD
For the position of the player (start, stop, etc.): see table
(principal diagram F).
• Check the clock signal at measuring point <71> This signal is
also present when only the mains switch is switched on.
Measurement point <71> captures when PLL captures.
For control of capture: see Annex II.
• Trigger the oscilloscope with signal at measuring point <72>
(=FSDE). Check the measurement points <76>, <77> and
<78> and their relationship to each other.
ERCO
For the position of the player (start, stop, etc.): see table
(principal scheme F).
• Check measuring point <94>.
• Check measuring point <79>
If this point is correct, the oscilloscope will trigger with
measuring point <79> (= FSEC).
• Check the measurement points <80> and <81> and their
relationship to each other.
• Check the UNEC signal (= measuring point <82>). Place test
plate 4A on the turntable.
Play track no. 15 or and verify measurement point <82>.
IMPORTANT:
If UNEC (measuring point <82>) remains continuously "high" it
is highly probably one of the ICs DEMOD, ERCO or RAM is
defective.
If the UNEC output functions normally and there is still no
music. is most likely one of the ICs CIM, FIL or DAC are
defective.
CIM
For the player's mode (start, stop, etc.). see table (principal
scheme F).
• Check measuring point <94>
• Check measuring point <84>
If this is good, then trigger the oscilloscope with measuring
point <84> (= STR1).
• Check the measurement points <85>, <86> and <87> and
their relationship to each other.
FIL
For the player's mode (start, stop, etc.). see table (principal
scheme G).
• Check measuring point <94>
• Check measuring point <84>
If this is good, then trigger the oscilloscope with measuring
point <84> (= STR1).
• Check measuring point <93>.
• Check the measurement points <90>, <91> and <92> and
their relationship to each other.
DAC
(Principal scheme 3).
In the "play" position, the analog signal (=music) is present at
the outputs of op-amp 6523 (=left) and op-amp 6525 (=right).
If necessary, check the KILL relay.
Annex I: LASER GIVES NO OR INSUFFICIENT LIGHT
The laser, together with the laser power supply and the
monitor diode, forms a feedback loop. A defect in the laser
power supply can therefore result in destruction of the laser.
When replacing the laser (= new light pen) it will also become
defective, since the original error in the laser power supply is
still present.
On the other hand, it is impossible to check and repair a
feedback system if a link is missing. For that reason, the so-
called "laser simulator" is supplied. Code number: 4822 395
30203 for lasers with negative supply voltage. and 4822 395
30215 for positive supply voltage lasers.
This laser simulator consists of a printed circuit board with the
laser and the monitor simulator, a switch to test the on/off
position and a number of connectors.
This print can be connected to the laser power supply instead
of the light pen so that the feedback system is closed.
Advertisement
