Bang & Olufsen Type 2651 Service Manual page 59

5 - 3
ADJUSTMENTS,
ENGLISH
Bang &Olufsen
Record current
CD
Laser current
reproduced. STOP must not be used. (Less bias produces a treble boost,
m o re b ia s a tr e b l e dr o p . )
- check the adjustment with an Fero, standard tape, part No. 6790067. lf
the result deviates significantly, adjust to the mean value between CrO/
FerOr.
- Remove the jumper across 2657 a{1ter the adjustment has been completed.
Place PCB 2 in service position (see dismantling, section 6).
short-circuit capacitor 2657 on PCB 7 (Automatic Level control off).
Connect an audio oscillator to the AUX input, 333 Hzl100 mV.
connect an AF voltmeter to test point 2 (3) on pcB 7 or to 2p21-5 (zp21r-6).
Load CrO, standard tape, part No. 6780135.
Carry out the procedure mentioned under TEST MODE 22 above.
Adjust the audio oscillator until 200 mV is measured.
Adjust 1633 (1634) on PcB 7 until the playback level is 200 mv by first
recording and then playing back 333 Hz. press AUX REC REc 22 every time
a recording is made and <STEP and TAPE every time the recorded piece is
to be reproduced. STOP must not be used.
The optical pick-up is extremely sensitive to static electricity. The work site
must therefore be protected against static electricity. Careless treatment of
the optical pick-up may reduce its life dramatically.
The CD drive mechanism and PCB 8 must be connected when the product is
connected to a mains outlet.
lmportant:
Preset the laser current potentiometer, 8R3813, when replacing the CD drive
mechanism, and check the connection to the monitor diode before
connecting the product to a mains outlet.
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Remove the rear panel (see dismantling, section 6).
Connect an ohmmeter from pin 18 to pin 27 of 81C7800.
Adjust 8R3813, coordinate 3D, until 1 Kohm is measured.
Connect a DC voltmeter across 8R3800, coordinate 3C.
Connect the product to a mains outlet, and press LOAD. Load test disc No.
5 (CD without errors, part No. 3634031).
Press cD. The voltage across 8R3800 must be higher than 15 mV,
otherwise the product has to be switched off and the error found.
lf the voltage across 8R3800 is higher than 15 mv, play track 1 on test disc
5 , a n d a d j u st 8 R 3 8 1 3 u n t i l 5 0 m V + 2 m V i s m e a s u re d .
NorE:
lf the voltage across 8R3800 is less than 25 mv, the CD may stop
shortly after having been started. The adjustment must therefore
be made immediately after starting.
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