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D150 power off thump


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#1 6502dude

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Posted 16 August 2005 - 10:59 AM

I have a D150 that I bought in late 1970s.

I had amp refurbished in 1981 by Remcron (in Canada) and upgraded to D150A with IOC added and the gain pots moved to front with new faceplate.

I haven't used this amp for about 6 years. It is boxed and stored. I was considering setting it up again as small system in the den.

I have noticed that shortly after amp is powered off, there is a low frequency thump heard on both channels.

Is this normal? Is there a fix for it?

My main system includes a pair of DC300A-II, each running bridged mono mode.

#2 DGlass

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Posted 16 August 2005 - 12:27 PM

It could be the plus and minus 10 volt power supplies are bleeding off non-symmetrically. Using an Oscilloscope it will need to be determined which supply is bleeding off the fastest. Starting with a 2.2 electrolytic capacitor add capacitance across to the faster side until you can get that side bleeding off as close as possible to the other.