SERVICE MANUAL
LBB 3310/00, 3330/00 and 3331/00 page: 28 Date of issue:
4822 861 11006 July 1998
10.3 Measuring instructions for the Delegate and Chairman unit (LBB3330/00,
LBB3331/00).
How to check if a Delegate or Chairman unit is correct is described in the next paragraphs. The items which are
described are:
• supply current
• internal supply voltages
• unit presence
• unit type
• microphone switch and light-ring.
• internal signals for Delegate and Chairman units
• the priority switch
Before you start measuring:
• Connect a Delegate and/or a Chairman unit to the CPSU.
• Turn the volume control of all Delegate and Chairman units in the maximum clockwise position (volume
maximum).
• Put the mode switch on the CPSU in the OPEN mode (1,2,3 or 4).
• Terminate the audio-output signal AUDIO-CONTR by connecting a 680 ohm resistor between M1 and M2 (or
between pin 1 and 2 of X11) of the Delegate or Chairman unit.
• Disconnect the loudspeaker from the Delegate or Chairman unit and connect a resistor of 25 ohm between pin 1
and 2 of X5.
10.3.1 Supply current
Measure the supply current from V+ by means of a current meter in the power supply line. This should be between
12mA and 22mA
10.3.2 Internal Supply Voltages.
Measure the internal supplies on the Units itself of +15V via M15 and +5V via M12, both related to M2 (= internal 0V):
a) at M15 this should be: +15V +/- 750mV
b) at M12 this should be: + 5V +/- 250mV
Note: From Data book, the IC itself is specified as +/- 250mV
10.3.3 Unit presence
To detect the presence of a unit, measure the voltage via M101 related to M8 (= internal 0V).
> 4.5 V = unit present.
10.3.4 Unit type
To detect the presence of a Delegate or Chairman unit, measure the voltage via M100 related to M8.
< 0.5V = Chairman Unit
> 4.5V = Delegate Unit
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