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PAS hum (full Curcio mod PAS)

68.36.41.59
Posted on May 24, 2003 at 17:22:33
airtime
Audiophile

Posts: 11323
Location: Arizona
Joined: February 4, 2003
 I jumped terminals 1&9 and 2&9 and the hum disappeared. So I'm going to compare the wiring from the original manual to the volume, blend and rear jack board.

There is no loudness tap and I removed the loudness circuit entirely. Also I never hooked up the phono board after installing the power module. BUT it didn't hum before I removed the loudness tap and the phono board wasn't hookup up then.

Any other suggestions to follow while I'll poking around the manual?

charles

 

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additional info, posted on May 24, 2003 at 17:47:20
airtime
Audiophile

Posts: 11323
Location: Arizona
Joined: February 4, 2003
 I placed a jumper from the volume pot ground to and additional ground and it decreased the hum by about 80%

charles

 

Re: PAS hum (full Curcio mod PAS), posted on May 26, 2003 at 07:35:57
Joe Curcio
Manufacturer

Posts: 1261
Location: Northern CA
Joined: October 10, 2001
 You have a ground loop - you can't assume all gorund connections are the same. _All_ the power ground connections from the audio boards should go to the power supply module (terminal numbers should match terminal numbers per the wiring diagram). The I/O ground connections (inputs & outputs and volume control) should terminate to (and only to) the line amp module.

The connection from the power module to the chassis ground should be via the single ground lead terminating at the quad cap.

 

Thanks will give it a check later, posted on May 26, 2003 at 09:42:53
airtime
Audiophile

Posts: 11323
Location: Arizona
Joined: February 4, 2003
 Thanks again Joe.
charles
PS finally learning how to use that scope. I even fixed a few stereos last week for some guy I know out west who resells them on ebay. I'm slowly inheriting my father in laws old electronic stuff. Got a AF/RF Lafayette sine generator. Sure the AF in only 400hz but I'm a newbie.

 

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