Test Of Master Link Data Receiver/Transmitter; Cd Laser Current; Exchange Of Microprocessor Module Pcb3 - Bang & Olufsen BeoSound 3000 2671 Service Manual

5.14 Repair tips, English

Test of Master Link DATA receiver/transmitter

CD laser current

Eyepattern

Exchange of microprocessor module PCB3

Test of the circuits 12TR30, 12TR31, 12TR52, 12TR53, 12TR55, 12TR56 and 12IC6.
- Lift P107.
- Mount on P4.
- Connect a square-wave generator 10kHz 0-5 V to P107-4 (transmit).
- Measure P107-2 (receive) with an oscilloscope; it should produce the same signal
as the one transmitted by P107-4, only here it is delayed by 10-15 µS.
To prevent that products connected via the Master Link socket destroy the data
communication in the case of an error in the data interface, the data interface
circuit has been designed so that components can be defective without causing a
malfunction.
For example, the diodes mounted in connection with Data- and Data+ are protection
diodes which will protect against static electricity.
Consequently, when making a repair, it may be necessary to replace/check several
components.
If 12TR55 is defective, both 12TR55 and 12TR56 should be replaced and the
diodes 12D4, 12D5, 12D19, 12D20, 12D21 and 12D22 should be checked.
If 12TR56 is defective, both 12TR55 and 12TR56 should be replaced and the
diodes 12D4, 12D5, 12D19, 12D20, 12D21 and 12D22 should be checked.
If one of the diodes 12D4, 12D5, 12D19, 12D20, 12D21 and 12D22 is defective,
all of the diodes should be replaced, and 12TR55 and 12TR56 should be checked.
Across 80R3121 (4.7 ohm) the measurement in mV will show the current in the
laser beam. Typical measure; ap. 300 mV. If over 450 mV the laser-head is defect.
The eyepattern can be measured between 80P1001 pin 5 and 80C2116 (1.3Vpp).
When exchanging PCB3 remember to insert the EEPROM from the defective
module, because it contains valuable data (serial no., type no., PIN-code etc.).
The data is not transferred to the new module untill you have been in contact with
the theft protection or after 12 hours connected with mains. This means that you
can try out a new PCB3 without transferring the products serial no. Etc..
Note !
When the serial no. has been transferred to the micro-processor it can only be
used for this specifi c product; it must go back to Bang & Olufsen's module repair
department as an exchange module to be erased again.
If the product functions are OK the theft protection is also OK; there is no need for
testing the functionality of the theft protection.
When the product is connected to mains, wait 20-30 sec. before operating.
All addresses in ML has to be updated after disconnecting mains voltage.