Marantz PM6010OSE KI Signature Amplifier Repair

Amplifier powering on.
Speaker protection relay no changing over.
Power input protection fuse T2.5 Amps failing after less than a minute.

The video shows the main Amplifier board and the speaker protection relay, as can be seen the relay outer casing is burnt and had been subjected to a lot of heat from the adjacent 10 ohm 3 Watt resistor R771.

The Amplifier was powered up via the Dim bulb tester and excess current was seen to be drawn as the bulb started to light.

Also the bias on the right channel rose sharply and was unstable hence why R771 was over heating and the protection fuse was blowing.

The rear back panel and main amplifier board fixing screws were removed.

R771 and the speaker protection relay was replaced.

Relay specifications 24 V DC DP/CO 5 Amps.

The resistors and transistors in the left channel were checked, Q758 2SD2033 was found to be open circuit collector to base.

Replacing Q758 fixed the over heating and bias issue.

As is the the case with all Marantz Amplifiers of this time period each board was removed and dry solder joints re-flowed.

The input selection switch was removed and cleaned with a fibre glass pencil and De-Oxit.

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

Bias for each channel set to 10 millivolts.

Power transformer was loose so the fixing bolt was retightened.

Due to the common ground connection the main amplifier board and rear back panel fixing screws including the speaker terminal fixing screws must be fitted. prior to testing.
If the Amplifier is powered up with out the common ground connection being made catastrophic failure of the output stages will be seen.

Amplifier fully tested working correctly.
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