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Note: In service loop B, the track is not only followed, but the
information is also displayed, provided the digital circuit is
functioning.
If one of the above conditions does not occur, in service loop
A, the following questions in the given order are answered
positively.
F. Does the (NOT)DO and HFL detector function?
(Measuring method see Sub F)
G. Is the track detector working?
(Measuring method: see Sub G).
H. Does the radial control function properly?
(Measuring method see Sub H).
If the answers to questions F, G and H are positive, the device
should be able to be brought into service loop B.
Third step (with a CD on the turntable).
Take the player out of the service loop by pressing the
play button. After a short whistle, the display shows the
number of tracks written on the CD. Servo µP 6201 now
responds to the information from the P line and the bus
(clock and information from the subcode).
Note that the player now not only follows the track, but also
can play the music if the digital and decoding circuit is OK.
If the above conditions do not occur, the questions below must
be answered positively.
I.
Does the P bit work?
(Measuring method: see Sub I).
J. Does the transfer of the subcode information work?
(Measuring method see Sub I).
K. Does T1 function. i.e. the polarity of RE?
(Measuring method: see Sub K).
If the answers to questions I, J and K are positive, the device
must be able to be brought into normal operating condition.
Fourth step (with a CD on the turntable).
If no signal can be heard in play mode, the last question must
be answered.
L. Does the digital decoding circuit function as specified?
(Measuring method - see Sub L).
Sub A. DOES THE LASER LIGHT?
Measurement method
Bring the player into service loop A without a CD on the
turntable.
Now the laser should light up indefinitely.
Another method, in which the laser lights for an unlimited time
and the objective remains stationary, is to remove plug A17
and bypass the lid switch. When the mains switch is switched
on, the laser must light up.
The checking is done with a light-sensitive component that is
slightly shielded from daylight.
Examples:
a. Connect a photosensitive diode BPW34, code number
4822 130 32108 with correct polarity to an analog
multimeter (e.g. PM 2412). When the laser emits light, the
meter will show almost full scale reading at 10 kΩ range.
b. Use a mobile phone camera and look for a tiny red dot.
c. Connect a photosensitive resistor 4822 116 10002 to a digital
multimeter PM 2517E.
When the laser gives light, the resistance drops to about 8 kΩ.
If the laser does not emit light, proceed to Annex 1
Sub. C. DOES THE LASER GIVE SUFFICIENT LIGHT?
Measurement method:
(Measuring points on preamplifier board, principal diagram E
and servo board, principal diagram C).
• Interrupt the collector of transistor 6230 or make pin 18 of the
servo µP "low".
• Disconnect plug A17: The laser should now continue to emit
light while FE, RE1 and RE2 are interrupted.
• Place a CD on the turntable and switch on the power.
• Inject directly with an LF generator (Ri ≤ 600Ω) at measuring
point <1> a sinusoidal signal of 2 Vpp, with a frequency
between 25Hz and 60Hz (the correct frequency depends on
the player).
• Set the frequency so that the monitor diodes in the light pen
output signals as indicated at metering points <5>, <6>, <7>
and <8>.
The amplitude should be between 40 mV and 80 mV.
If the amplitude is insufficient, proceed to Annex I.
Sub. D. DOES THE LENS ENTER FOCUS?
Measurement method
• No CD on the turntable
Turn on the power switch and press the play button.
The arm should now go to the center. Immediately afterwards,
the objective must move 4X (2X when using servo uP MAB
8440) up and down to find the focus point. After that, the action
stops. These actions are controlled from the servo µP.
If the lens does not move, check the servo µP, the focus circuit,
or the focus coil.
• With CD on the turntable
Fast method
To check globally whether the focus circuit is functioning,
proceed as follows:
• Place a record on the turntable.
• Bring the player into service loop A.
• Remove the CD from the turntable.
• Now check whether the objective focuses by placing a
reflective part (e.g. mirror for angle measurement) above it.
Detailed method
• Check transistor 6230 (on the servo board, principal diagram
C) as follows:
Check that FN goes low for a short time with each pass of
the nominal focus point.
Only if focus point FN is found, FE will be enabled through
transistor 6230 (base becomes negative). Check whether the
base of 6230 is controlled "low" from the servo µP (= FCO).
If this is not the case. then check the servo µP. If 6230 is sent
"low", continue.
• Test the focus circuit as follows:
Interrupt the collector of 6230 (or make point 18 of the servo
µP "low"), remove plug A17 and switch on the mains.
The laser now gives continuous light, FE is released and the
focus loop is also interrupted at measuring point <1>
(=FE) on the servo board, principal diagram C.
(=FE) on the servo board, principal diagram C.
Testing the circuit between measuring point <1> and focus coil
Testing the circuit between measuring point <1> and focus coil
(measuring points on the servo board, principal diagram C).
(measuring points on the servo board, principal diagram C).
• Inject directly on measuring point <1> by means of an LF
• Inject directly on measuring point <1> by means of an LF
generator (Ri ≤ 600Ω) a sinusoidal signal of 10Hz, 2Vpp.
generator (Ri ≤ 600Ω) a sinusoidal signal of 10Hz, 2Vpp.
• Check whether the focus coil — so also the objective —
• Check whether the focus coil — so also the objective —
responds.
responds.
• Check whether the voltage at measuring point <2> is 1Vpp.
• Check whether the voltage at measuring point <2> is 1Vpp.
• Check whether the voltage at measuring point <3> is 9Vpp.
• Check whether the voltage at measuring point <3> is 9Vpp.
• Check whether the voltage at measuring point <4> is 8Vpp.
• Check whether the voltage at measuring point <4> is 8Vpp.
Testing the sub-chassis (measuring points on the pre-amplifier
Testing the sub-chassis (measuring points on the pre-amplifier
board, principal diagram E and the servo board, principal
board, principal diagram E and the servo board, principal
diagram C).
diagram C).
• Inject directly at measuring point <1> a sinusoidal signal
• Inject directly at measuring point <1> a sinusoidal signal
between 25Hz and 60Hz with 2Vpp, by means of an LF
between 25Hz and 60Hz with 2Vpp, by means of an LF
generator (Ri ≤ 600Ω). The correct frequency is player
generator (Ri ≤ 600Ω). The correct frequency is player
dependent.
dependent.
• Set the frequency so that the monitor diodes in the light pen
• Set the frequency so that the monitor diodes in the light pen
give output signals as indicated at the measuring points <5>,
give output signals as indicated at the measuring points <5>,
<6>, <7> and <8>.
<6>, <7> and <8>.
• Check the measuring points <9>, <10>, <11> and <12>.
• Check the measuring points <9>, <10>, <11> and <12>.
• Check measuring point <13>.
• Check measuring point <13>.
• Check measuring point <14>
• Check measuring point <14>
The signal at this measuring point is equal to the signal at
The signal at this measuring point is equal to the signal at
measuring point <13>, but the amplitude depends on the
measuring point <13>, but the amplitude depends on the
position of bias resistor 3158.
position of bias resistor 3158.
If all checks are positive close the focus loop by refitting plug
If all checks are positive close the focus loop by refitting plug
A17. The focus circuit should now function.
A17. The focus circuit should now function.
It should be noted that the amplitudes at measuring points <5>
It should be noted that the amplitudes at measuring points <5>
to <13> are somewhat dependent on the characteristics of the
to <13> are somewhat dependent on the characteristics of the
monitor diodes.
monitor diodes.
Sub. E. DOES THE TURNTABLE MOTOR RUN AND IF SO, IS
Sub. E. DOES THE TURNTABLE MOTOR RUN AND IF SO IS
IT RUNNING AT THE RIGHT SPEED?
IT RUNNING AT THE RIGHT SPEED?
Measuring method (measuring points on the servo board,
Measuring method (measuring points on the servo board,
principal diagram C)
principal diagram C)
• Put a CD on the turntable and put the device in service loop
• Put a CD on the turntable and put the device in service loop
A.
A.
• Once the focal point has been found, check at metering point
• Once the focal point has been found, check at metering point
<15> whether FCO is low.
<15> whether FCO is low.
If not, check the focus circuit (see Sub D).
If not, check the focus circuit (see Sub D).
If FCO is low, continue.
If FCO is low, continue.
• Only switch on the mains, remove plug A52 and check the
• Only switch on the mains, remove plug A52 and check the
MCES signal (on the decoding board near the decoding µP)
MCES signal (on the decoding board near the decoding µP)
at measuring point <66> see figure F. The amplitude can be
at measuring point <66> see figure F. The amplitude can be
between 0.5V and 2.5V depending on the setting of the coil in
between 0.5V and 2.5V depending on the setting of the coil in
the PLL circuit.
the PLL circuit.
If the MCES signal is not correct, check the DEMOD and ERCO
If the MCES signal is not correct, check the DEMOD and ERCO
circuit, see Sub I.
circuit, see Sub I.
If the MCES signal is correct, continue.
If the MCES signal is correct, continue.
• Refit plug A52, remove plug A14 on the pre-amplifier board
• Refit plug A52, remove plug A14 on the pre-amplifier board
and inject a DC signal of 2.5V into the connector of plug A14.
and inject a DC signal of 2.5V into the connector of plug A14.
(= turntable motor). Note polarity. The turntable motor should
(= turntable motor). Note polarity. The turntable motor should
now be running. (Due to the DC voltage of 2.5V the rotational
now be running. (Due to the DC voltage of 2.5V
speed of the motor is approximately equal to the rotational
speed associated with the scanning of the inner tracks).
• Bring the device into service loop A.
With a DC voltage < 2.5V, figure G must be visible at
measuring point <66>.
With a DC voltage > 2.5V, figure H must be visible at
measuring point <66>.
The same difference must be measured at point <17>. If the
signal at measurement point <17> is correct, check the
turntable motor circuit between measurement point <17> and
the turntable motor.
If the signal at measuring point <17> is not correct, check
whether the MCES signal is released by FCO at the output of
IC 6205D.
Method.
Interrupt the MCES signal at pin 1 of IC 6205D (= interrupt
the jumper 57-58 on the servo board). Now if the MCES
signal is correct, check the circuit around IC 6205D.
If the MCES signal is not correct, restore the connection 57-
58 and proceed as follows:
Remove the device from the service loop by switching off the
power switch. Now consecutively press the mains switch and
the PLAY button (The turntable motor rotates through the
gain-injected DC voltage of 2.5V).
Check the eye pattern at metering point <65>. The eye
pattern can be stabilized by manually moving the light pen
under the tracks or by pressing the FWD key for
approximately (5 sec.)
If the eye pattern at point <65> is not present or
stable, check the HF preamplifier (see Annex V). When the
eye pattern is correct, continue.
• Put the device in service loop A.
(The turntable motor dreads the injected DC voltage of
2.5V).
Check whether the signal at measuring point <55> (= HFL)
is correct, see figure Y.
If the signal is not correct, check the HFL detector circuit (=
circuit between the measuring points <65> and <55>). If the
HFL signal is correct, continue.
• Take the device out of the service loop by switching off the
power switch. Consecutively press the power switch and
the PLAY button. (The turntable motor is powered by the
injected DC voltage of 2.5 V).
• Check the capture of the PLL circuit of the DEMOD-IC, see
Annex II.
If the PLL captures then continue.
• Check the timing signaled at the output of the DEMOD-IC
coals is indicated in Sub L.
When the timing signals are correct, continue.
• If the MCES signal is still not properly present, replace the
affected specific digital IC by trial and error using the
service IC box, code number 4822 395 30194.
• The MCES signal should now be present and correct.
Sub. F. DOES THE (NOT)DO AND HFL DETEKTOR
WORK?
Measuring method (measuring points on the servo board.
Principle diagram C)
• Starting point:
HFL = 1 if the spot is exactly on the track.
HFL = 0 between tracks (e.g. during track jumping).
(NOT)DO = 0 or DO = 1 at drop-cut.
(NOT)DO = 1 or DO = 0 with no drop-out.
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