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Chasing 60 hz hum

I have an MC 7150 and an MC 7104 in my system, both plugged in to the same circuit on a power strip. The problem is that McIntosh went away from two prong and moved to 3 prong grounded wiring when the 7104 came along. I also moved from a C39 to an MX119 preamp, again the change from ungrounded to grounded. Having these units together on the same circuit produces a nice fat 60 Hz hum. To cure this, I used cheaters (3 to 2 adapters) on the 3 prong devices and this works.......mostly. Then, every few months the hum comes back and I go to the strip, wiggle one of the adapters a little bit and it stops....but this is a pretty goofy way to run an otherwise nice railroad....anyone got any ideas that are not radical (such as rewire the house!)
broimp

Showing 1 response by ths364

ths364
181 posts
 
Does the 7150 have a two-prong cable? If it has a non- polarized plug, take a voltage reading from the chassis to the screw that holds the wall-outlet cover in place. Reverse the plug and take a reading again. The plug orientation with the lower voltage reading should be the quieter of the two.
2) The filter capacitors in these components power supplies are supposed to filter out 60 cycle hum after the line voltage has been rectified."Leaky" or worn out caps will not filter the ripple, leading to increased hum. In older equipment replacing the caps might be worth looking into.
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