Question about Mcintosh MC602 2-Channel Amplifier

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Mcintosh mc7150 lights dim on higher volume

I bought this power amp used. It looks brand new though it is 15 years old. when i put the volume half way up, the blue lights of the amp start dimming on intense music(bass) and I think  the punch is lost. the sound is clear and open but it seems there is an aging component inside . I am not an expert but I wonder if those power supply capacitors could be  the culprits . Any help would be highly appreciated. Note: I use a dedicated AC outlet for this amp

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Yes you could be right about the power supply capacitors as they have a tendency to dry out. Another tip is to inspect the terminations of these capacitors and clean their contact points as often the screw and screw boss is a different metal and corrosion and electrolysis occurs between these and the main power supply connectors. If in doubt clean with a scotch scourer till shiny metal is exposed on connection points. Then coat contacts with electrical contact conditioner (lanolin grease is good too) before reassembly.

Some amplifiers do not have sufficient storage to sustain high bass levels into difficult speaker loads, the Mac should not be one of these however . To verify that your dedicated AC outlet is not a limiting factor - use a power board and plug an incandescent lamp into the same point as the amp and see if you see any flickering of lamp when the amp lights dim.

If no evidence of limiting of main power and connection maitenance does not solve the issue, replacing the capacitors is indicated.

Posted on Feb 17, 2010


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