McIntosh C-24 preamp

Discussion in 'McIntosh Audio' started by Tube Radio, Dec 4, 2017.

  1. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    I have two questions about my McIntosh C-24 preamp.

    1. It has three broken slide switches and I decided to remove the front panel to look at them and see how hard they are to change. Two more snapped off and that's when it hit me how they probably broke.

    One switch had been replaced and it also has the factory mod with the springs pressing against the control shafts.

    So at some point the front panel was removed again and the three switches broke because the panel wasn't removed straight .

    Is there any place other than McIntosh that has the proper or similar switch?

    2. I noticed the left channel the treble seems a little off slightly at times.

    What's odd is I can set the switch to stereo reverse and it seems to be right, although at certain times everything seems fine in normal stereo.
     

     

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  2. Pio1980

    Pio1980 AK Member Subscriber

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    Angel Station, Alabama
  3. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    Thanks for the link.

    Those are just what I need.
     
  4. Pio1980

    Pio1980 AK Member Subscriber

    Messages:
    25,290
    Location:
    Angel Station, Alabama
    I refurbed a C24 a few years ago, the slide switches looked identical to those in Dynaco preamps, and several other period components.
     
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  5. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    Haven't ordered the switches yet.

    Will do so soon.

    Might use some screws nuts and star washers to secure the switches so that I can easily replace them in the future if needed.
     
  6. rollcentre

    rollcentre Boom-tizzz

    Messages:
    526
    Location:
    DFW,TX, United States
    Is it common for the switches on these units to break? Do you think for normal use? Or just the front panel not being put on right?

    Also, do these preamps have lights behind the lettering on the facia? It seems like every picture of one I see lit up, only the power indicator light illuminates on the front.

    I am curious because one popped up and I'm interested. Under the hood it looks nice and simple.
     

     

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  7. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    Only the power light is lit. The panel isn't unfortunately.

    The switches can break off if the panel is not taken off evenly from both sides.

    All the electrolytic caps will need to be replaced other than the main two caps if not already done.
     
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  8. BilboBaggins

    BilboBaggins AK Subscriber Subscriber

    Messages:
    3,213
    Location:
    Ottawa, Canada
    I had a C24 and quite liked it. The switches were fine on my unit, mind you it was only ever opened up in the McIntosh Clinic or by my very good tech. I've not seen too many of them around though.
     
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  9. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    Mine was opened at some point by someone who didn't know what they were doing.

    Found a shorted electric cap keeping one channel from working.
     
  10. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    I had been having an issue of intermittent connections of some of the RCA jacks and just always ignored it since things worked most of the time.

    When I found the left channel was doing it as well and that the left channel was unusually lower in volume most of the time I decided to fix it.

    Saw the RCA jacks were all dirty on the outside.

    I had some #000 steel wool so I used that to clean the jacks on the outside.

    No more bad connections and I do believe the left channel is at the same level as the right now, but I cannot be sure as this flu has my ears messed up somewhat still.
     
  11. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    So apparently I have a device that uses the same switches and didn't know it.

    Just disassembled a solid state Heath kit oscilloscope intending on making it a scope clock and while removing the DPDT slide switches I noticed they looked an awful lot like the ones on my C-24 preamp.

    Just brought in a set of three to compare and they look identical (at least the style and length of the actuating handle looks the same) so it looks like soon as I get the time, I can replace the switches in the C-24 for a grand total of $0.00 :banana:

    In fact I don;t think I have anything invested in the preamp other than the $10 I paid for it as I already had the other things I needed to fix the problem it originally had of a dead channel.
     
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  12. BilboBaggins

    BilboBaggins AK Subscriber Subscriber

    Messages:
    3,213
    Location:
    Ottawa, Canada
    That’s awesome! Congrats! It’s a very nice preamp! I had one for a few years.
     
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  13. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    Thanks.

    Yes it is a very nice preamp.

    Recently wound up adding a TL-082 OP-AMP internally to the record output so that I can connect the record out to pretty much any impedance. Was necessary for integrating it with the equipment I have that records.
     
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  14. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    Here's a photo of the switches.

    The switch handles are shorter, but I think that I like it better.

    Also will make the switches less prone to breakage.

    20180513_235655-800x600.jpg
     
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  15. Mike Gibson

    Mike Gibson Modulator Staff Member Super Mod Subscriber

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    Looks good to me. I agree about the shorter handles being less prone to breakage.
     
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  16. twiiii

    twiiii Addicted Member

    Messages:
    5,761
    Location:
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    I was always surprised how much better the phono section of a C-24 was compared to a C-22. There was big difference in the performance below 300 HZ. The 24 was slightly noiser on line inputs than a 22, but the phono stage really surprised me. And if you adjusted the amp levels you could keep the noise from becoming an issue. Even a C-26 could be noisier than a C-22 line stage. That's why I waited for a C-28. Klipschorns and big Altecs were always a problem until you got the interface between the amps and power amps adjusted for best signal to noise ratio . Especially if you were using big power amps.
     
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  17. Tube Radio

    Tube Radio Super Member

    Messages:
    3,451
    With mine I am thinking using modern equivalents for the transistors will make it a bit quieter.
     

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