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AR P-10 Power Amp


djcheung
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Hi all,

Just acquired the C-06 and P-10 last week.

On first power on, I have noticed that it hums a bit on both channels and the right channel is louder than the left with just the speakers connected. Otherwise it sounds reasonably good. My 3as sound a bit fuller and more solid. When the volume is turned up, the hum is not noticeable.

On opening the cover on the P-10 to have a peek, I have noticed that it has been opened before with some screws missing and the support bracket for the RCA inputs missing. I have also noticed that one of the solder pad on the speaker connection board has been lifted off the circuit board, luckily the solder is still holding firm.

My skill is limited only on 'like for like' parts replacement. 

Can this humming noise be fixed or I should just play it and enjoy ?

Does anybody here have one of these ?

Best regards,

David.

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Hum at idle - especially in both channels - can be due to a power supply issue, usually aged/defective filter capacitors or diodes.

You can download a service manual for the P-10 at the HiFi Engine website: https://www.hifiengine.com/manual_library/acoustic-research/p-10.shtml

Honestly, I wouldn't run the risk of damaging your AR-3a speakers with a dicey power amplifier - a lot can go wrong. It's a nice amplifier, and certainly worth servicing for proper performance.

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Thanks ar_pro,

I have a copy of the service manual. But not being electronically trained, I wouldn't even know where to start. I have been trying to find a shop locally here in Cambridge,UK but without success. A good shop is quite hard to come by in this corner of the world!

I will keep looking.

David.

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Thanks ar_pro,

I just had another quick test to see where the hum is coming from.

1. I connected the speakers with no inputs connected. Power on, only hear hum from within the equipment. No hums from the speakers.

2. Connect the power amp to the preamp with the preamp not connected to anything and not plugged in to the power socket. No hums

3. Connect the power amp to the preamp with the preamp not connected to anything but now connected to the power socket but with power button off - HUMS

Any suggestions ? I know this is difficult without seeing the unit physically.

Best regards,

David.

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