Philips CD304 MK II - Laser Functionality Checks

Note that the set is not only tracking a song in loop B, but
also playing the song, provided the digital circuit is
working.
If this does not work, return to service loop A and answer
the questions below positively in the sequence given.
F Are DO and HEL detectors functioning?
(test method: see sub F)
G. Is track detector functioning well?
(test method: see sub G)
H. Is the radial contro! functioning properly?
(test method: see sub H)
If the answers to questions F, G and Hare positive, it should
be possible to bring the player in service loop B.
Third step (with disc on turntable)
Release the set from service loop B by pressing the
START/REPLAY key on the display during playback of a
musical number that is present on the disc.
Note that the set is not only tracking a song in loop B, but
also piaying the song, provided the digital circuit is
working.
Sub. A. IS THE LASER GIVING LIGHT?
Test method
Bring the player in service loop A without placing a disc on
the turntable. Now the laser is giving light for an unlimited
period of time.
Another method for which the laser gives light during an
unlimited period of time and the objective is standing still,
is disconnecting plug 24 on the servo PCB and connecting
point 24-3 of the cable connector to ground.
In case of power-on the laser should burn. This is checked
with the aid of a light-sensitive component which is slightly
screened from ambient light.
Hereafter follow some examples:
a. Connect photosensitive diode type BPW34, code num-
ber 4822 130 32108, with correct polarity to an analogue
multimeter (e.g. PM2412) at range 10 kN.
If the laser is burning, the meter will give virtually full
scale deflection.
b. Connect LDR, code number 4822 116 10002, to digital
multimeter PM2517E.
If the laser is burning, the resistance will drop to approx.
8k.
If the laser is not giving any light, proceed to Annex |.
Sub. C. 1S THE LASER GIVING SUFFICIENT LIGHT?
Test method (Test points on Pre-amp PCB)
— Interrupt the collector of TS6230 on the servo PCB or
ground the - side of electrolytic capacitor 2209. Disconnect
7-3
plug 24 on the servo PCB and connect pin 24-3 (laser) of
the cable connector to ground.
Now the laser should continue to give light while FE,
RE1 and RE2 are interrupted.
— Place disc on turntable and switch power on.
— Directly inject with AF generator (Z; < 600 Ohms) to
test point » FE a sine-wave signal between 25 and
60 Hz (exact frequency is player-dependent) and 2 Vpp.
— Select such a frequency that the monitor diodes of the
light pin give output signals as indicated on test points
®, &, ® and ®. Amplitude 40 - 80 mV.
— lf the amplitude is not sufficient, proceed to
Annex I.
Sub. D. IS THE OBJECTIVE COMING INTO FOCUS?
Test method
® No disc on turntable
Switch power on and actuate Play button.
Now the arm should move inwards. Immediately after that
the objective should move two times up-and downwards
(this happens during searching of the focusing point).
After this the action will stop.
These actions are software-controlled from the servo uP.
If this is not working, check uP servo, end stage focus cir-
cuit or focus coil.
¢ With disc on turntable
Quick test procedure:
For a rough check on the working of the focus circuit,
proceed as follows:
— place disc on turntable.
— set player in service loop A.
— remove disc from turntable.
— now examinate if the objective focuses by bringing a
reflective object (e.g. mirror) above it.
Detailed test procedure
— Check TS6230 (on servo PCB) as follows:
Check whether FN becomes, with each passage of the
nominal focusing low for a short period of time. Only
when focusing point FN has been found, FE will be
released via TS6230 (base will become negative).
Check whether base of TS6244 is driven low from ser-
vo uP (= FCO). tf not, check servo uP.
If so, proceed.
— Test focusing circuit as follows:
Interrupt the collector of 6230 on the servo PCB and dis-
connect plug 24 on the servo PCB. Connect pin 24-3
(laser) of the cable connector to ground.
CS 5 221GB