Bang & Olufsen Type 2651 Service Manual page 58

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Bang &Olufsen
5 - 2
ADJUSTMENTS, ENGLISH
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Speed
Load Wow tape, part No. 6780037 (the adjustment must be made at the
centre of the tape).
Connect a Wow/Flutter meter or a frequency counter to 2P21-5 (L OUT).
Press TAPE. After 30 seconds'operation, adjust 3705 on PCB 11 to 3,150
Hz +0.3o/o (see section 6 for service position of PCB 11).
Load Torque cassette, part No. 6780046.
Place PCB 2 in service position (see dismantling, section 6).
Press TAPE, and adjust 1635 on PCB 7 to a take-up torque of 45-50 g-cm.
Use a Pegel Level reference tape 250 pWb/mm, part No. 6780035 (*Level
reference tape 200 pWb/mm is mentioned as an alternative in brackets*):
- Place PCB 2 in service position (see dismantling, section 6).
- Connect an AF voltmeter to test point 8 (9) on PCB 7 or to 2P21-5 (2P21-6).
- Press TAPE, and then press MODE until NR is flashing in the display (the
noise reduction system is disconnected).
- Adjust 1631 (1632) on PCB 7 to 620 mV (*550 mV/200 pWb/mm*).
The tape recorder noise reduction system is connected automatically when
r e co r d i n g .
Electric recording adjustments in the tape recorder section must be made
with the noise reduction system disconnected, which is done in test mode:
?r
Take-up torque
Playback level
TEST MODE 22
HX filter
t \
Connect the product to a mains outlet.
Within 30 secs., press: . 2650. The display reads: 8888 when the product is
in test mode.
Press AUX REC REC 22 (22 = disconnection of noise reduction system).
Te s t m o d e is a b a n d o n e d b y p r e ss i n g ' o r d i s co n n e c t i n g t h e m a i n s v o l t a g e '
Place PCB 2 in service position (see dismantling, section 6).
Short-circuit capacitor 2657 on PCBT (Automatic Level Control off).
connect a DC voltmeter to |c7710 pin 6 (13) on PCB 7.
L o a d C rO, st a n d a rd t a p e , p a rt N o . 6 7 8 0 1 3 5 .
Carry out the procedure mentioned under TEST MODE 22 above.
Adjust coil5627 (5626) on PCB 7 to minimum DC voltage.
Remove the jumper across 2657 afier the adjustment has been completed.
Place PCB 2 in service position (see dismantling, section 6).
Short-circuit capacitor 2657 on PCBT (Automatic Level Control off).
Connect an audio oscillator to the AUX input, 333 Hzl30 mV.
Connect an AF voltmeter to test point 2 (3) on PCB 7 or to 2P21-5 (2P21-6).
Load CrO, standard tape, part No. 5780135.
Carry out the procedure mentioned under TEST MODE 22 above.
Ad j u st t h e a u d i o o sci l l a to r u n t i l 3 0 m V i s m e a s u r e d .
Adjust 1626 (1627) on PCB 7 until the playback level at 333 Hz and 12,500
Hz is the same (approx. 30 mV) by first recording and then playing back
333 Hz and 12,500 Hz. Press AUX REC REC 22 every time a recording is
made and <STEP and TAPE every time the recorded piece is to be
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Bias