Robertson Forty Ten noise problem

nfakbc · 24th November 2010, 11:20 PM

I have a robertson forty ten amplifier that I am having a noise problem through the left channel. The strange thing is the noise is loudest with no RCA cables plugged in but once I do plug them in most of the noise goes away (although not completely). I opened up the amp and see no burned components, checked for any loose grounds but found none. I took a few electronics classes years back in school but don't have much experience, any ideas of what to look for would be greatly appreciated.

djk · 25th November 2010, 01:44 AM

There may be an open resistor from the input ground to chassis ground, usually 10R or less.

nfakbc · 25th November 2010, 02:28 AM

Thank you for the quick response. I see the main chassis ground, what exactly are you talking by the input ground?

djk · 25th November 2010, 11:02 AM

http://users.ece.gatech.edu/mleach/l...aphics/ckt.pdf

R51 on this diagram.

http://www.hafler.com/techsupport/pd...00_amp_man.pdf

R45 on this diagram.

24th November 2010, 11:20 PM	#1
nfakbc diyAudio Member Join Date: Mar 2008	Robertson Forty Ten noise problem I have a robertson forty ten amplifier that I am having a noise problem through the left channel. The strange thing is the noise is loudest with no RCA cables plugged in but once I do plug them in most of the noise goes away (although not completely). I opened up the amp and see no burned components, checked for any loose grounds but found none. I took a few electronics classes years back in school but don't have much experience, any ideas of what to look for would be greatly appreciated.

25th November 2010, 01:44 AM	#2
djk diyAudio Member Join Date: Feb 2001 Location: USA	There may be an open resistor from the input ground to chassis ground, usually 10R or less. __________________ Candidates for the Darwin Award should not read this author.

25th November 2010, 11:02 AM	#4
djk diyAudio Member Join Date: Feb 2001 Location: USA	http://users.ece.gatech.edu/mleach/l...aphics/ckt.pdf R51 on this diagram. http://www.hafler.com/techsupport/pd...00_amp_man.pdf R45 on this diagram. __________________ Candidates for the Darwin Award should not read this author.

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25th November 2010, 02:28 AM	#3
nfakbc diyAudio Member Join Date: Mar 2008	Thank you for the quick response. I see the main chassis ground, what exactly are you talking by the input ground?

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