Bang & Olufsen Type 2651 Service Manual page 60

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Bang &Olufsen
5 - 4
ADJUSTMENTS, ENGLISH
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TOUDSPEAKER
Adjustment of bass/treble level
TEST MODE 13
Replacement of PCB 2 Amplifier
H a s to b e ca rri e d o u t o n l y wh e n r e p l a c i n g a s p e a k e r u n i t , P CB 2 A m p l i f i e r ,
PCB 3 Microprocessor or 31C4.
This test mode allows manual adjustment of the bass and treble levels of the
sp e a ke r s, a n d i t is a vai l a b l e i n s ta n d -b y o n l y .
- Connect the product to a mains outlet.
- Within 30 secs., press: o 2650. The display reads: 8888 when the product is
in test mode.
- Pre ss 1 3 .
The present adjustment is shown in the display:
' X ' = l e f t t r e b l e .
' X ' = l e f t b a s s .
' X ' = r i g h t t r e b l e .
'
X ' = ri g h t b a s s .
Test mode is abandoned by pressing . or disconnecting the mains voltage.
Connect the new PCB 2 Amplifier with the exception of 2P28 (R OUT) and
2P2s (L OUT).
Transfer the label concerning speaker adjustment from the old PCB 2 to
the new PCB 2.
Connect an AC voltmeter to that speaker unit which has the weakest
output according to the label.
LB (left bass): X.XX VAc 2P29-3 RB (right bass): X.XX VAc 2P28-3
LT (left treble): X.XX VAc 2P29-1 RT (right treble): X.XX VAc 2P28-1
Left ground:
2P29-2
Right ground: 2P28-214
C o n n e ct a n a u d i o os c i l l a to r t o t h e A U X i n p u t .
Bass : 700 HzJl mY.
Treble : 7200 HzJl mV.
Carry out the procedure mentioned under TEST MODE 13 above.
Adjust to maximum output: Display = 9999. lf necessary, select speaker by
means of STEb (the active speaker flashes) and then press 9.
Press STORE.
Press AUX.
Pre ss n u n t i l t h e vo l u m e r e a c h e s m a x i m u m ( d i s p l a y = 7 2 ) . A d j u s t b a l a n c e ,
bass and treble to neutral level, and loudness off.
Adjust the audio oscillator output voltage until:
the voltage on the AC voltmeter = weakest output on label.
Measure and make a note of the voltage at the three other speaker
outputs by means of the AC voltmeter:
LB (left bass, 700H2):
X.XX VAc 2P29-3
LT (left treble, 7200H2):
X.XX VAc 2P29-1
Left ground: 2P29-2
RB (right bass, 700H2):
X.XX VAc 2P28-3
RT (right treble, 72O0Hz): X.XX VAc
2P28-1
R ig h t g r o u n d : 2P28-2t4
The difference between the rated voltage stated on the label and the
measured voltage has to be calculated for the three speaker units:
1*::l::?." =^
Measured voltage
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