I recently acquired a Marantz 1150D integrated amp that has a hum on the phono inputs only..I have cleaned all controls and checked for poor grounds etc but nothing.. Anyone have the same problem and can steer me in the right direction.? \I do not know if this amp is rare but my son was going to recycle it just beforeI took it Cheers Wayne

 

Is the hum there with the phono inputs shorted to ground?

 

Every time I have encountered audio 'hum' problems it has always been due to a grounding issue with the source audio(phonograph in your case) or the amp.

 

I have tried the phono shorting plugs and the hum is still there... The issue, at least from what I can see, is that the problem would be in the preamp board area.. I do not have a service manual, but will try to get one to proceed. As I said I am not familiar with this Marantz Model..At this point the only issue is the phono circuit, all other inputs are fine and hum free. Once I get a schematic/service manual, this will help..

Thanks for the replies and if anyone else had a similar issue let me know...

Cheers... Wayne

 

ok, if its in the preamp, does the hum disappear when the volume is at minimum, it should go away on minimum vol and be there on max vol, if the hum is there on minimum volume its in the main amp or psu.



service manual

http://www.electronica-pt.com/esquema/audio/marantz-audio/marantz-1150d-20430/