macman007
Mcintosh..Made In USA
Hi folks, the faithful 1200 has developed a hiccup lately. Seems after playing a while, especially very quietly, or when sitting idle in between titles, after about an hour of running, I hear quietly very quietly a buzz with some 60hz , going up and down. It comes and goes, for about a minute, then goes away. I have isolated the 1200 from any room or other circuit influences, as well as other gear, even swapped speakers. I use my 1200's pre amp center channel to feed signal to a powered subwoofer, which times out after while if no music plays, When the hum-buzz begins, you hear the relay trying to kick on the sub's idle shutdown relay. I get the buzz from the speaker with everything else, even the other speaker, subwoofer, and all other peripherals and cables disconnected.
My thought is one or more caps are beginning to break/broken down and letting DC pass, perhaps a output coupling cap for the left channel. Everything on this unit is original, except the power supply board protect relay caps, I got a pair of NOS caps from Catrafter 15 years ago now for a buzzing protect relay. This is different. I've owned/ its been in my family since brand new, so I know it's complete history
Its planned to recap it 100% this year, I'm actively trying to get a decent cap list together. You'd think someone would have one posted here, or several for that matter, as with other Marantz's. There are a few 1200's out there after al.
Should anyone reading this have an idea based on experience which cap(s) are failing, if my suspicions are correct ( think they are) please reply to this post. I just need to get a few more months out of the unit, till I get my other preamp back in service after the holidays. Then this one is relegated to the bench for an overdue overhaul.
I have measured the speaker outputs, there is no more than the specified DC voltage on either channel at anytime, even with the buzzing. I tried the speakers on both speaker system terminals. The buzz is till there on the left channel, with the very quiet 60hz tone thru-out..
Thanks and happy holidays!
My thought is one or more caps are beginning to break/broken down and letting DC pass, perhaps a output coupling cap for the left channel. Everything on this unit is original, except the power supply board protect relay caps, I got a pair of NOS caps from Catrafter 15 years ago now for a buzzing protect relay. This is different. I've owned/ its been in my family since brand new, so I know it's complete history
Its planned to recap it 100% this year, I'm actively trying to get a decent cap list together. You'd think someone would have one posted here, or several for that matter, as with other Marantz's. There are a few 1200's out there after al.
Should anyone reading this have an idea based on experience which cap(s) are failing, if my suspicions are correct ( think they are) please reply to this post. I just need to get a few more months out of the unit, till I get my other preamp back in service after the holidays. Then this one is relegated to the bench for an overdue overhaul.
I have measured the speaker outputs, there is no more than the specified DC voltage on either channel at anytime, even with the buzzing. I tried the speakers on both speaker system terminals. The buzz is till there on the left channel, with the very quiet 60hz tone thru-out..
Thanks and happy holidays!
