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McIntosh MC2105

Discussion in 'McIntosh Audio' started by briandrex, Jul 7, 2018.

  1. briandrex

    briandrex AK Subscriber Subscriber

    Messages:
    90
    Location:
    Chesapeake City, MD
    Just picked up a 2105 amplifier with wood case in decent shape. Only problem it was known to have was the cracked glass front which I planned on fixing at a later date. Using a Marantz 2270 as a pre. Hooked everything up and get very faint sound out of the left channel. Swapped the cables at the pre-out on the Marantz and still have the same problem which narrows it down to the amplifier. Tried different speakers and speaker cable and still very weak left channel. Have some static when I turn the Left Gain all the way up and jiggle it.

    Proceeded to take the bottom off the amplifier and really deoxit the Right and Left Gains. Worked them each a good 100-150 times each until they were really smooth. Let everything dry and then hooked back up with the same problem. I'm thinking my next step is to take this somewhere to be serviced. Would have liked to have sampled it a little before the service call but thinking that I may not get that lucky. Just wanted to see if there is anything simple I could look for. I got the unit for a great deal so not worried about a service/restoration bill if it comes to that sooner than later.
     
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  2. AlTinkster92

    AlTinkster92 AK Subscriber Subscriber

    Messages:
    3,255
    Location:
    NC
    Don't use Deoxit D-5 on pots, only Faderlube. Good luck with your project :)
     
  3. c_dk

    c_dk Addicted Member

    Messages:
    6,240
    Location:
    West Michigan
    Did you Deoxit the slide switch on the back......adds a capacitor in series with the input to use with certain old tube preamps that would leak some DC, especially upon turn on.

    Cleaning a bad speaker switch is usually not effective for this amp, a plastic part in the switch fails, but would not hurt to try to get some Deoxit in there.

    The speaker switch is no longer available so splicing the wires or jumping the soldered connections are your options.
     
    Last edited: Jul 7, 2018
  4. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    26,482
    Location:
    Angel Station, Alabama
    If the slide switch is same as on C24, replacements are available.
     
  5. briandrex

    briandrex AK Subscriber Subscriber

    Messages:
    90
    Location:
    Chesapeake City, MD
    I used faderlube as well. Why no deoxit on the POTS? Is there plastic that could be harmed?
     
  6. briandrex

    briandrex AK Subscriber Subscriber

    Messages:
    90
    Location:
    Chesapeake City, MD
    I have not used the deoxit on the slider switch on the back. What is that switch for? I did notice some crackling and static in the left side when I slid it up and down. I guess it's time to open it up again and clean that switch as well. Right side sounds fantastic just want to here it in stereo now lol. As far as the speaker switch is concerned....since it have power to the right side would a dirty or back switch fail to only one side such as the left? You can here sound from the left but it's very weak unless you only listen to the left by itself and really turn the volume up.
     

     

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  7. briandrex

    briandrex AK Subscriber Subscriber

    Messages:
    90
    Location:
    Chesapeake City, MD
    Just did it and I have sound on the left channel now. Sounds great thank you for the help! Still want to get this restored. Will hopefully get it up to Audio Classics one day or locally around the Maryland, Delaware New Jersey area. Had really good results with my MAC 1700 at Brandywine Electronics in Bear, DE.
     
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  8. damacman

    damacman Blown and Injected Subscriber

    Messages:
    8,601
    Location:
    Gilbert, AZ
    The MC2105 is worthy of restoration. After a refresh, it will run circles around many modern designs from other manufacturers. I've owned several.

    Enjoy!
     
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  9. kevzep

    kevzep Its all about the Music Subscriber

    No lubricating properties, you should be using Deoxit SN5 Shield (Blue) after applying deoxit DN5 (red) as it just removes all the oxidation and leaves a fresh surface ready for more oxidation.......
    You must only use Fader Lube (Green) in Pots.
     
  10. twiiii

    twiiii Addicted Member

    Messages:
    6,222
    Location:
    west Texas
    The speaker on and off switch is where I would look first. Plug in a pair of headphones and see what you get. Do the needles indicate power through the amp? The input connectors can be a big issue, too.
     
  11. yurka77

    yurka77 AK Subscriber Subscriber

    Messages:
    880
    Location:
    Bethel, CT
    i had this issue on my amp when i first got it. As recommended here, I cleaned the sliding INPUT switch in the back and both channels work great now
     

     

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