Question about Marantz PM-68 Amplifier

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Marantz PM-74D it powers up and i can get the lights to work but no sound or power being generated by the unit any ideas

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  • ciara4 Oct 11, 2008

    Marantz-PM66SE Amp suddenly stopped working Power light on but no sound. Trouble shooting of manual no help. Have tried all the obvious solutions power switch, speaker cables, volume control ect with no joy. Please help

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Your no doubt finding the speaker safety/turn on surge protect relay NOT engaging a few seconds after turning it on-right? Check the output transistors. These are the big green and black ones screwed to the heatsink. You gain access to them by taking off the bottom cover. There's 4 per channel--2 green and 2 black. You'll probably find one or more of them shorted. If you find replacements, put them in exactly as the originals with new thermal grease/heatsink compound. Unsolder and lift the center pin (collector) on each of the four transistors of the effected channel. Power it up and check across the outside pins of each device for proper bias-about a half a volt or so on each one. If the voltage is much higher, or not there you've got other problems that will require more diagnostic/troubleshooting. Do all the lights on the front panel work-or just the tape monitor indicators? If just the tape monitors light up, check resistors RN83 and RN84 on main board under the speaker connector board-remove the speaker connector board to get at them. These are bad on mine and I've yet to replace them. I believe these to be 920 ohm 1% precision resistors....

Posted on May 26, 2008

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