intermittant preamp (HK AVR8000)

dakota137 · 21st October 2007, 11:45 AM

The left front channel failed in my Harman Kardon Amplifier. It has individual preamp outputs as well as power amp inputs on the back for each channel, and I was able to determine that the poweramp for the channel is fine, (via hooking up the preamp out to a separate power amplifier and having the same problem). (I also checked the affected speaker)

The channel will work normally for about 5 minutes (independent of analog or digital source, DTS/DOlby digital, 5.1 or stereo, and volume), but then will cut in and out and proceed to work only at a very low, barely audible level. It will usually start working again if I turn the amplifier off, then back on.

So far I've ran some compressed air through the amp (trying to dust it off, it's not too dusty), reset the processor, and haven't been having any luck.

Any ideas? It's out of warranty but I do have a service manual. I live in Japan so any help is much appreciated as service centers are nonexistent over here! Are these symptoms of a bad capacitor or transistor? I don't know where to start. Thanks!

myhrrhleine · 22nd October 2007, 03:06 PM

It's hard to answer because there are so many possibilities.
Personally, i'd start by checking the solder joints.

warm up/ resolder each joint.

dakota137 · 24th October 2007, 02:49 PM

Thanks... I also noticed that it:

a) affects the headphones as well

b) if I move the amp around, it'll cut in and out...

21st October 2007, 11:45 AM	#1
dakota137 diyAudio Member Join Date: Oct 2007	intermittant preamp (HK AVR8000) The left front channel failed in my Harman Kardon Amplifier. It has individual preamp outputs as well as power amp inputs on the back for each channel, and I was able to determine that the poweramp for the channel is fine, (via hooking up the preamp out to a separate power amplifier and having the same problem). (I also checked the affected speaker) The channel will work normally for about 5 minutes (independent of analog or digital source, DTS/DOlby digital, 5.1 or stereo, and volume), but then will cut in and out and proceed to work only at a very low, barely audible level. It will usually start working again if I turn the amplifier off, then back on. So far I've ran some compressed air through the amp (trying to dust it off, it's not too dusty), reset the processor, and haven't been having any luck. Any ideas? It's out of warranty but I do have a service manual. I live in Japan so any help is much appreciated as service centers are nonexistent over here! Are these symptoms of a bad capacitor or transistor? I don't know where to start. Thanks!

22nd October 2007, 03:06 PM	#2
myhrrhleine diyAudio Member Join Date: Jan 2006 Location: Avalon Island	It's hard to answer because there are so many possibilities. Personally, i'd start by checking the solder joints. warm up/ resolder each joint. __________________ Just because you can't hear it doesn't mean no one can.

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24th October 2007, 02:49 PM	#3
dakota137 diyAudio Member Join Date: Oct 2007	Thanks... I also noticed that it: a) affects the headphones as well b) if I move the amp around, it'll cut in and out...

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