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
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
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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.
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?
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?
Attachments
Here's the difference from original 2200 and MKII. I posted this some time ago. Came directly from Tony:
http://www.diyaudio.com/forums/solid-state/85978-diffirent-between-parasound-2200-mark-ll.html
http://www.diyaudio.com/forums/solid-state/85978-diffirent-between-parasound-2200-mark-ll.html
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.
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I have a HCA-1200 which has a 120hz hum from the chassis. Everything disconnected except for the power.
I find the hum annoying. Took it to sertechelectronics in town and the fellow there just said it is likely the transformer de-laminating and I just have to deal with it.
I find that the hum gets louder sporadically and quietens down again. Doesn't seem to sync up with anything else in the house.
I also notice the left side of the amp is quite a bit warmer than the right side. Is the indicative of a problem?
I only have basic electrical knowledge but happy to investigate further if instructed.
Is it safe to poke around when its powered off? Do the caps discharge when switched off?
I find the hum annoying. Took it to sertechelectronics in town and the fellow there just said it is likely the transformer de-laminating and I just have to deal with it.
I find that the hum gets louder sporadically and quietens down again. Doesn't seem to sync up with anything else in the house.
I also notice the left side of the amp is quite a bit warmer than the right side. Is the indicative of a problem?
I only have basic electrical knowledge but happy to investigate further if instructed.
Is it safe to poke around when its powered off? Do the caps discharge when switched off?