McIntosh Modifications

Discussion in 'McIntosh Audio' started by Mike Gibson, Oct 28, 2012.

  1. Rich Andrews

    Rich Andrews Well-Known Member

    Messages:
    921
    Location:
    TX
    That task isn't something that the average man-in-the-street could handle. It is one of things that if you have to ask how to do it, you should not attempt it..
     
  2. smartin53

    smartin53 AK Subscriber Subscriber

    Messages:
    439
    Location:
    Denver
    Well...it MAY be simpler than anyone thought. I was independently researching MAC1700 mods and came across this thread...

    http://audiokarma.org/forums/showthread.php?t=91542

    It goes into some details on converting the tape output into a preamp out. Ultimately it SEEMS he simply clipped and isolated the tape output, and then ran a shielded wire to the outputs from the preamp boards. The following post indicates where the signal came from.

    http://audiokarma.org/forums/showpost.php?p=972885&postcount=31

    From the discussion, it seems it works well. I'm curious if this makes sense and if anyone had any further thoughs. It is obviously doable.

    I've been juggling the option of switching from my MA6100 to the MAC1700 and then running the audio into my Dynaco ST-70 tube amp. I'd of course need this mod to do that.
     
    Last edited: Jan 13, 2013
  3. dewickt

    dewickt Will fix about Anything

    Messages:
    3,377
    Location:
    Knoxville, TN
    I recently converted an MA230 the same way using the tape head jacks as the amp in and the phono 2 as the preamp out. On a 230 with the 4 gang volume control you can end up with a gain control for the amp in and also a gain control for the preamp out.
     
  4. mrz80

    mrz80 I guess it's in my blood

    Messages:
    602
    Location:
    Gainesville, FL
    Curse you AudioKarma, I've got enough projects on my "this 'll never get done but it's on the to-do list anyway" list! :) I'd pretty much managed to forget all about my long ago notions of modifying my 1700 for pre-out/amp-in; now you guys've got me thinking again about it. I'd reached the conclusion after some brainstorming that it'd be a major undertaking involving ditching the courtesy AC outlets (does anyone actually *use* those in the modern age of outlet strips?) to gain some back panel real estate. I figured on making up a "filler" panel, moving the speaker outs over to where the AC outlets were, and putting pre-out/amp-in RCAs where the speaker outs were. I'd considered but rejected repurposing the Tape Head and Phono2 jacks for pre-out/amp-in, since I was also considering redoing the Tape Head input (and maybe Phono2 as well) as another line-level Aux input. Maybe I ought to go ahead and put this project back on the list, since the unit needs major surgery now anyhow (I have to recap the unit, chase down the high distortion in the phono preamp, and repair the dead FM tuner). Food for thought, food for thought... :)
     
  5. hapichai

    hapichai New Member

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    3
    new thread? anyhow, a newly acquired mc30

    it's rough, i'm wondering how to test the tranny.. one looks questionable. clearly, the output transformer. wires look like they got hot. one coupled cap in the board had a bad solder. i resoldered. was planning on using a lighter gauged fuse, and bringing it up on a variac. This particular one came from a military base. i can provide pics, specifics.. before stepping up to the plate and recapping it, etc. i at least want to know if it's a go, or just a ebay boat anchor.. thanks, rich
     
  6. ADiG

    ADiG New Member

    Messages:
    3
    hi, someone can tell me how many millivolts is the bias voltage of the power section amplifier MA7000?
    in my Mc MA7000 the values ​​are different and left heatsink up more heat.
    you could read the schematic diagram at the "heat sink" page, but is not available online
    Many thanks
     
    Last edited: Aug 5, 2014
  7. ADiG

    ADiG New Member

    Messages:
    3
    there is a technical MC in this forum, who knows the value in mv. be set?
    Around the forums, I've read several posts with the same problem (the left channel of the ma7000 warming). Perhaps there was an error setting this value in the assembly ...
    by my measure, it is not very clear about the difference measured between the two channels:
    left 10.00 mv. - Right 5.7 mv.
    I brought the left channel to 6.00 millivolts and does not heat up more, but knowing the exact value, I would stay in peace!
    Thanks to those who helped me
     
  8. ADiG

    ADiG New Member

    Messages:
    3
    I warmly thank Ron C. and Mr. Landon from Mcintosh Lab for the support lent me - thank you!
     
    KentTeffeteller likes this.
  9. drillher

    drillher AK Subscriber Subscriber

    Messages:
    1,664
    Location:
    Upstate,N.Y.
    My Mc240 had a thicker power cord installed and other than some electrical tape wrapped around the cord where it exits the chassis,there is no strain relief.Should I remove the tape and install a strain relief in the chassis if I can find one that fits without enlarging the hole in the chassis?
     
  10. damacman

    damacman Blown and Injected Subscriber

    Messages:
    6,161
    Location:
    Gilbert, AZ
    Yes! And that is exactly what you need to do to properly secure it.
     
  11. dewickt

    dewickt Will fix about Anything

    Messages:
    3,377
    Location:
    Knoxville, TN
    Original cord was 16 gauge two conductor non polarized, for an amp that never draws over 2.5 A this is more than adequate. I use neoprene HPM heater cord that I found on Amazon, forget 3 wire grounded cords, the 240 will have ground loop humm due to its design and not knowing how the power transformer is wound (winding start unknown).
    The grommet is a Heyco SR-4K-4, chassis hole of .5", and flat cord.
     
    John James likes this.
  12. drillher

    drillher AK Subscriber Subscriber

    Messages:
    1,664
    Location:
    Upstate,N.Y.
    Thanks Terry.
     
  13. cardoctordav

    cardoctordav New Member

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    43
    How is this for a mod?
     

    Attached Files:

  14. cardoctordav

    cardoctordav New Member

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    43
    I was done by necessity, the old board was broken!
     
  15. cardoctordav

    cardoctordav New Member

    Messages:
    43
    Are UF5404's a bad idea in a 240?
     
  16. wayne glenn

    wayne glenn New Member

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    5
    I have a mx130 mated to two mc2105's running klipsch RF-7's bi amped, I am wondering if the mx130 can be made a contender or should I just put my money into a better analog pre amp?
     
  17. c_dk

    c_dk Addicted Member

    Messages:
    5,111
    Location:
    West Michigan
    What is a contender? Everyone's definition is different.

    The MX130 is a outdated theater preamp tuner.....but it certainly, in certain areas, will outperform a older stereo preamp (certainly if it has not been restored) both in noise, distortion and convenience....it has a tuner and a remote control.

    Have you had your MC2105 amps restored or at least recapped?
     
  18. wayne glenn

    wayne glenn New Member

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    5
    That is on my to do list, I need to figure out which caps I should replace and which are the best sounding at a good price
     
  19. wayne glenn

    wayne glenn New Member

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    5
    As I contender I'm speaking sound quality , especially vinyl
     
  20. AbSoundLabsMN

    AbSoundLabsMN Absolute Sound Labs

    Messages:
    37
    Location:
    Minneapolis, MN (Savage) - 55378
    We have used Hakko soldering equipment for years. With the exception of some of the soldering irons, all of the rework stations and temp controlled stations are grounded thereby offering static protection. Of course, using a static wrist band is a good addition. Our Hakko equipment are very reliable and have been in service for over 10 years.
     

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