Experiencing a mysterious hum in a Parasound HCA-2200 II. - diyAudio
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Old 16th February 2014, 05:35 AM   #1
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Default Experiencing a mysterious hum in a Parasound HCA-2200 II.

I have a hum that comes through the speakers. It doesn't change when I adjust the volume control, but it does get slightly louder as the amp warms up.

I read the manual and tried to bypass the ground with a cheater plug. No luck. So I took it to an authorized Parasound technician and he said he couldn't hear the issue. I figured it was the power at my house. Since then I have tried it at 4 different houses and the same thing happens everywhere.

I don't think the tech was lying. I honestly believe he couldn't hear it. It's pretty subtle. The tech says that he tested capacitors and everything was in spec.

Any ideas? Can someone help me out with a schematic? I'd like to be loaded with information for when I take it to a different tech.

BTW, this is my first post here. I am an active member at AudioKarma, but thought I'd branch out and try for help here. To say that I am a novice would be an understatement. I may not fully understand your advice, haha, but maybe I can take some of it to the tech.

Nick

Last edited by nickrobotron; 16th February 2014 at 07:28 PM.
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Old 18th February 2014, 01:18 AM   #2
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Any tips or advice out there?
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Old 18th February 2014, 02:18 AM   #3
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I saw a schematic for the original 2200 here somewhere, but I don't think it was complete, and I don't know what the differences are.

Isn't this a JC design? Any info out there on this amp guys?
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Old 23rd February 2014, 04:09 AM   #4
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It would help if we knew if you had a 120hz or 60hz hum. Also do you have the jumper pin on the XLR connectors? As far as the power supply caps, I have not seen one of them test good. I have rebuilt several first ver's and MKII all in need of re-cap and power resistors. Another problem is the poor soldering done by the Chinese. I have seen more than one lead barely soldered in of just plane broken loose. Also check ALL of the connections to the main caps and grounds. Even though they have sealant on them I still find them loose. If you need the schematic let me know. I have posted somewhere the BIAS setting procedure, just do a search.
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Old 23rd February 2014, 07:10 AM   #5
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The attached Google'ed schematic is for revision I HCA-2200 amps. Information from Parasound states that are no major circuit topology changes for your revision II, mainly a better PCB layout.


When you ground both amplifier inputs, do you hear a hum? 60Hz? If both channels hum, the shared main power supply is a good place to start measurements, and checks for a loose ground connection.

With one input grounded, and one input connected to your preamp, do you hear a hum? Alternate inputs? Good suggestion to remove+plug+remove+plug scrub clean the jumper pins on the XLR connectors?

Can you test the amp with an alternate input source? Capacitor coupled or battery powered?
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File Type: jpg HCA_2200 schematic.jpg (639.1 KB, 50 views)
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Old 23rd February 2014, 07:15 PM   #6
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Here's the difference from original 2200 and MKII. I posted this some time ago. Came directly from Tony:
Diffirent between Parasound 2200 and Mark ll
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Old 26th February 2014, 08:51 AM   #7
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Quote:
Originally Posted by LineSource View Post
The attached Google'ed schematic is for revision I HCA-2200 amps. Information from Parasound states that are no major circuit topology changes for your revision II, mainly a better PCB layout.


When you ground both amplifier inputs, do you hear a hum? 60Hz? If both channels hum, the shared main power supply is a good place to start measurements, and checks for a loose ground connection.

With one input grounded, and one input connected to your preamp, do you hear a hum? Alternate inputs? Good suggestion to remove+plug+remove+plug scrub clean the jumper pins on the XLR connectors?

Can you test the amp with an alternate input source? Capacitor coupled or battery powered?
That's the scat I was looking for...

Need some feedback from OP to go any further.

Oh, and thank's Ed...this one might end up on my bench, so your input is appreciated.

Last edited by EchoWars; 26th February 2014 at 08:56 AM.
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