Help! Strong hum from transformer

some1x · 1st December 2007, 12:06 AM

I have been using a N.E.W A-20.1 amplifier (based on Pass design?) for a while. Today, for no reason, the transformer started to hum very loudly.

I didn't make any modifications to the amp, change any components in my system, move the amplifier, etc. There was no hum yesterday

I opened the top cover to check out the transformer. It is very securely fitted between two metal plates with rubber sheets in between. Don't know what is wrong.

Anyone who can recommend a way to fix or diagnose the problem?

eyoung · 1st December 2007, 12:21 AM

hello all...

a high current draw will cause the transformer to make more mechanical noise ck your bias current each channel make sure you are not geeting ready to have a meltdown..

good luck, Elwood

some1x · 1st December 2007, 12:22 AM

Thanks for the fast reply. How do I check bias current? I have a generic DMM somewhere...

eyoung · 1st December 2007, 01:24 AM

allrighty then... howze about a schematic??? to peruse...

Elwood

some1x · 1st December 2007, 12:25 PM

I don't have one

The problem fixed itself after I reconnected everything on the amplifier. Lucky

eyoung · 2nd December 2007, 12:40 AM

that was easy enough... glad i could be of service, it's what i do best...nothing.

good luck E.

some1x · 9th December 2007, 03:05 AM

arrgh! The hum randomly resurfaced. Guessing something is wrong with the amp after all. Don't have a schematic because the amp is like 15 years old and there is no literature on it. Is there anything that can be figured out from these pictures?

http://www.cs.mcgill.ca/~nyu3/IMGP1971.JPG
http://www.cs.mcgill.ca/~nyu3/IMGP1972.JPG

tiltedhalo · 9th December 2007, 03:33 AM

If the amp functions properly and the hum from the trans is random you might have DC riding the AC mains.

some1x · 9th December 2007, 03:40 AM

Is there any way to test for that? Is it safe to measure DC in the AC mains using a DMM?

some1x · 9th December 2007, 04:24 AM

Its gone again lol. Maybe it does have something to do with AC mains.

1st December 2007, 12:06 AM	#1
some1x diyAudio Member Join Date: Jan 2006 Location: montreal	Help! Strong hum from transformer I have been using a N.E.W A-20.1 amplifier (based on Pass design?) for a while. Today, for no reason, the transformer started to hum very loudly. I didn't make any modifications to the amp, change any components in my system, move the amplifier, etc. There was no hum yesterday I opened the top cover to check out the transformer. It is very securely fitted between two metal plates with rubber sheets in between. Don't know what is wrong. Anyone who can recommend a way to fix or diagnose the problem?

9th December 2007, 03:33 AM	#8
tiltedhalo diyAudio Member Join Date: Sep 2005 Location: Melbourne Florida	Hum If the amp functions properly and the hum from the trans is random you might have DC riding the AC mains.

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1st December 2007, 12:21 AM	#2
eyoung diyAudio Member Join Date: Aug 2007 Location: Sunny SC,USA 15 min south of Charlotte NC	hello all... a high current draw will cause the transformer to make more mechanical noise ck your bias current each channel make sure you are not geeting ready to have a meltdown.. good luck, Elwood

1st December 2007, 12:22 AM	#3
some1x diyAudio Member Join Date: Jan 2006 Location: montreal	Thanks for the fast reply. How do I check bias current? I have a generic DMM somewhere...

1st December 2007, 01:24 AM	#4
eyoung diyAudio Member Join Date: Aug 2007 Location: Sunny SC,USA 15 min south of Charlotte NC	allrighty then... howze about a schematic??? to peruse... Elwood

1st December 2007, 12:25 PM	#5
some1x diyAudio Member Join Date: Jan 2006 Location: montreal	I don't have one The problem fixed itself after I reconnected everything on the amplifier. Lucky

2nd December 2007, 12:40 AM	#6
eyoung diyAudio Member Join Date: Aug 2007 Location: Sunny SC,USA 15 min south of Charlotte NC	that was easy enough... glad i could be of service, it's what i do best...nothing. good luck E.

9th December 2007, 03:05 AM	#7
some1x diyAudio Member Join Date: Jan 2006 Location: montreal	arrgh! The hum randomly resurfaced. Guessing something is wrong with the amp after all. Don't have a schematic because the amp is like 15 years old and there is no literature on it. Is there anything that can be figured out from these pictures? http://www.cs.mcgill.ca/~nyu3/IMGP1971.JPG http://www.cs.mcgill.ca/~nyu3/IMGP1972.JPG

9th December 2007, 03:40 AM	#9
some1x diyAudio Member Join Date: Jan 2006 Location: montreal	Is there any way to test for that? Is it safe to measure DC in the AC mains using a DMM?

9th December 2007, 04:24 AM	#10
some1x diyAudio Member Join Date: Jan 2006 Location: montreal	Its gone again lol. Maybe it does have something to do with AC mains.

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