Cambridge Azur 640P Phono MM MC Pre Amplifier Repair

Fault
Pre-Amplifier not powering on, and the curse of the brown glue.

The 640P uses an external 12 Volt 1.3 Amp AC power adaptor, although the unit only draws a maximum of 500 milliamps.

The 12 V AC output was checked and found to be missing, the power adaptor input resistance was checked across the live and neutral pins.
Internal Transformer open circuit.

A compatible replacement power Adaptor was connected to the unit and the 640P powered up.

The video shows the power supply section of the unit and the usual brown glue covering many components.

In all cases the glue must be removed as it becomes conductive and corrosive resulting in component failure.

Eye protection should be worn to prevent any glue flakes flicking up and causing injury.

The video shows the extent of the problem, the following components were replaced due to glue contamination.

R43 150 ohm
R30 100 ohm
R42 82 ohm
D3/D4 1N4004 Rectification Diodes

The pre-Amplifier fully tested and working correctly.

Note: The Audio output relay takes approximately 15 seconds to change over after power up, this must be taken into account before testing the operation of the 640P after repair.

[gerardohernandez]

Hello, I have this same model and the fault is similar. The LED turns blue, I have both voltages of 18 volts. but the voltage of 5 volts does not reach the relay, what component sends those 5 volts? . I have tried to follow the line but it is difficult without the diagram. Greetings!