Marantz PM30 Amplifier Repair

Intermittent loss of Audio both channels.

This issue is very common and caused by oxidization of the input selection switch and speaker protection relay contacts.

The video shows the input selection switch and the high level of oxidisation, the switch was cleaned with a fibre glass pencil and De-Oxit.

The speaker protection relay was replaced 24 V DC DP/CO.

The following work was also carried out.

Rear back panel and main Amplifier board chassis fixing screws removed.

Dry solder joints re-flowed on the following.
Input RCA Sockets
Interconnecting plugs and sockets
Output transistor and driver transistors mounted on the heat sinks
Main ON / OFF Switch
Balance and Head Phones sockets

All user controls and switched cleaned with De-Oxit to ensure reliable noise free operation.

Bias for each channel set to 14 millivolts.

Note: When testing after repair the fixing screws for the Amplifier board and rear back panel including the speaker terminal fixing screws must be fitted to complete the common ground connection.

Failure to do the above and powering up the Amplifier would result in catastrophic failure of the output stages.

Amplifier fully tested working correctly..
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