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ART Pro Channel Mic Pre noise troubleshooting help.  Schematics, MP3 & Pics.
ART Pro Channel Mic Pre noise troubleshooting help.  Schematics, MP3 & Pics.
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Old 20th June 2020, 10:49 PM   #11
MarcelvdG is offline MarcelvdG  Netherlands
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Join Date: Mar 2003
Location: Haarlem, the Netherlands
Is the voltage at pin 8 correct?
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Old 21st June 2020, 01:33 AM   #12
BassAmp is offline BassAmp  United States
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Join Date: Mar 2016
Location: CA
Yes, pin 8 is getting +15VDC

Last edited by BassAmp; 21st June 2020 at 01:37 AM.
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Old 21st June 2020, 05:03 AM   #13
MarcelvdG is offline MarcelvdG  Netherlands
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Join Date: Mar 2003
Location: Haarlem, the Netherlands
It could be a broken down A7 or no DC path from ground to pin 3. You have checked R119, but is the connection between R119 and pin 3 OK? That is, if you measure straight from pin 3 to the ground plane with the supply off, do you also get 7.99 kohm? If so, then I think it has to be A7.
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Old 21st June 2020, 10:02 PM   #14
BassAmp is offline BassAmp  United States
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Join Date: Mar 2016
Location: CA
I just measured from pin 3 to the ground plane and I am getting 7.99K. I'm hoping that replacing A7 will bring this back to life. Fingers crossed.

While I have this thing torn apart, and since I need to place a parts order, is there anything I should replace on general principle? The larger power supply caps maybe? I suppose I could recap the whole thing but that might be overkill. Any suggestions?

Thanks again for all the help.
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Old 27th June 2020, 02:46 AM   #15
BassAmp is offline BassAmp  United States
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Join Date: Mar 2016
Location: CA
I am VERY happy to report that replacing A7 with a new TI NE5532P has completely solved the problem. The hiss is gone and the VU meter now works as it should. It may seem like a very minor repair but I find this very exciting and rewarding. Thanks to everyone who contributed. I sincerely appreciate it.
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