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Problem Description
EURO 4 / EURO 4H and EURO 4D Chassis (All models)

Unit Stuck in Standby. When the product is switched on the picture appears, and then the unit
switches to standby.
Problem Resolution
Close attention should be paid to the standby power supply circuit of Q852. This will need to be
monitored. The collector voltage should read approximately 7.5volts D.C. It has a zener diode
linked to the base circuit of 5.6volts dc by D573. It is important to remember that the base voltage
is linked the emitter ensuring that the voltage is held at 5volts dc on the emitter.

This 5volts dc on the emitter supply is extremely important it is the regulation supply for
microprocessor IC 1101 and EPROM IC 1102, the EAROM IC1103 and the Reset IC1104 and
IC1105 and therefore should not drift.

Once this supply is checked the main IC1101 needs to be examined via pins 3, 4, the 6 MHz
crystal is oscillating correctly and serial clock and data lines are correct amplitude (5volts peak to
peak). Pin 71