No Ir/Display O.k; Display Does Not Work Fir Is Ok. 4~3 4; Fault In The Display - Bang & Olufsen Beo4 1624 Reparaturanleitung

Bang&Olufsen
Table 1
No IR/display O.K.:
Display does not work/IR is OX.:
Fault in the display:
4-4
REPAIR TIPS, ENGLISH
The keyboard switches can be ohmed between the test points (1 - (6 and
R1 - R6
(remove
the batteries first). Connection is made between the
contact points when the key in question is pressed.
C1 C2 C3 C4 CS
C6
R1
RADIO MENU
LIGHT
0 TV
TEXT
R2
CD
YELLOW
AV
...
SAT
GREEN
R3
A.TAPE
»
RECORD
GO
V.TAPE
«
R4
9
BLUE
8
"
7
RED
RS 6
EXIT
5
A
4
LIST
R6 3
•
2
,
1
STOP
Does the display identification change when pressing RADIO, TV, SAT,
etc.
If yes, replace the module (PCB).
If no, check the keyboard (see "Keyboard does not work").
If the keyboard is O.K., replace the module (PCB).
Check the connection between the display and the module; the nuts at
the display should be tight but not overtightened. If one or several
dots are missing in the display, the reason might be that one of the
nuts is too tight/loose. Observe the display text while adjusting the two
nuts.
Check the crystal X1 by means of an oscilloscope, the test point is
shown in fig. 2. The crystal should oscillate constantly at 32kHz,
corresponding to a period of approx. 30j.Js.
Check the LCD voltages V1 - V4 (see fig. 2) with an oscilloscope,
measured relative to Vcc (plus (+) on the SMD electrolyte capacitor):
V1~-1VD[
V2,., -2V
DC
V3 "" -3VD(
V4 .. -4VD(
Any ripple on the voltages in question may be due to a short circuit
between the display and the module.
Check and carefully clean with isopropyl alcohol the contact surfaces
and the contact rubber which establish the connection between the
display and the module.
(NOTE! Never touch the contact surfaces or the contact rubber with
your fingers!)
If one dot is missing in the display, the fault is probably in the display.
If a number of dots are missing, carefully clean the connection
between the display and the module (see Display does not workllR is
O.K.). The problem could also be a direct fault in either the display or
the module.