Grand Concerto Humm

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ha_kiwi
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Grand Concerto Humm

Postby ha_kiwi » Sat May 28, 2011 5:35 am

I imported a Grand Concerto from the USA and am running it through a tramsformer to Convert our 220 Volt to the USA 110 Volt. I brought the unit some time and had a brain dead moment when I plugged it in and I connected to the 220 Volt. I'm so used to dual voltage power supplys anyway it blew the fuse. I replaced the fuse and now have it running on 110 Volt. All appears well keypads work but I get a humm out of the speakers even with no sources attached. Can anyone suggest anything ?

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kevind
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Re: Grand Concerto Humm

Postby kevind » Sat May 28, 2011 12:46 pm


ha_kiwi
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Re: Grand Concerto Humm

Postby ha_kiwi » Mon May 30, 2011 2:28 am

Because the Humm is happening with no sources attached I can't use a ground loop eliminator device that attaches to the source and then to the amp input. What would I use to try and eliminate the hummm ?? I'm pretty green at this

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CinemarDave
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Re: Grand Concerto Humm

Postby CinemarDave » Mon May 30, 2011 10:16 am

My guess is that the filter capacitors in the power supply were damaged by the high voltage applied to them. They are now letter some of the AC ripple pass through on to the DC mains. I had a power surge do something similar to this to me a while back. You might be faced with having to replace the power supply.

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Mr. Spock
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Re: Grand Concerto Humm

Postby Mr. Spock » Sun Nov 06, 2011 3:53 pm

If the power supply in the GC uses a typical fast-blow glass fuse I doubt the filter caps got damaged. They are electrolytics and typically take seconds of overvoltage time (at 2x the input voltage) to get damaged. My suspicion would be that the GC power supply was designed for 60Hz and you are now running it on 50Hz.

A simple test would be to disconnect all audio inputs and view the DC from the power supply on an DMM (AC voltmeter) or oscilloscope. There should be less than 1V of AC.
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Re: Grand Concerto Humm

Postby ha_kiwi » Wed Nov 09, 2011 9:51 pm

Thanks for the info. In the end I sent it to the NZ Distributor and they had to replace all six amps :(

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Re: Grand Concerto Humm

Postby Mr. Spock » Thu Nov 10, 2011 10:14 pm

Ouch.
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