McIntosh Modifications

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

  1. Mike Gibson

    Mike Gibson Modulator Super Mod Subscriber

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    This thread is for modifications to McIntosh equipment. All I ask is that they be tried & tested changes before you post them. Thanks.
     
  2. dewickt

    dewickt Will fix about Anything

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    How not to Mod/update

    I don't mind helping out as long as I have time, just don't bite off more than you can handle. Good soldering practices and neat workmanship count with McIntosh, they were works of art when new, lets keep them that way.
     

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  3. c_dk

    c_dk Addicted Member

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    Study the schematics to learn how the variious gain stages work and shape the spectral balance of the sound and create spurious noise.

    Study the convoluted reference grounding and shielding (or lack there of) used as best pre 80s practices and implement new solutions.

    Beware of marketing department engineered products as solutions.
     
    Cosmicmes likes this.
  4. Rich Andrews

    Rich Andrews Well-Known Member

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    C22 mod - extended HF response

    To extend the HF response flat to about 22 KC remove C19 and C20, 33 pf caps.

    In stock form my C22 started to roll off at about 18kc.
     
    Last edited: Oct 29, 2012
  5. Rodeodave

    Rodeodave hates ground loops

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    in the Alps
    When working with the turret boards in classic McIntosh amplifiers, be sure to mount new parts (usually resistors) to the same specs as McIntosh engineers did.

    A sturdy mechanical connection of a part ensures a secure and conductive solder joint later. It's not hard to do, looks neat and is superior in function.
     

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    Last edited: Oct 29, 2012
  6. Rich Andrews

    Rich Andrews Well-Known Member

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    Lowering the noise floor of the MC2500

    I don't know how to convert my MC2500 mod page to the forum so I am not going to try.

    The easiest part to perform is the re-routing of the fan wires and the move of the thermoswitch from one heat sink to another one.

    http://rich.homeunix.com/mc2500/mc2500mod.html
     
  7. Rich Andrews

    Rich Andrews Well-Known Member

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    A Soldapullt does a nice job removing excess solder from a joint so that the original part can be unwound from it's post.

    [​IMG]
     
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  8. MX117.MC7150

    MX117.MC7150 Listener Subscriber

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    Nice "how not to" photo's. :thumbsdn:
     
  9. c_dk

    c_dk Addicted Member

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    What kind of modifacations are members looking for....future serviceability....added reliability......."sound"?
     
  10. John James

    John James "Bob's your uncle" (Stolen) Subscriber

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    Yeah. :D
     
  11. c_dk

    c_dk Addicted Member

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    A number of us posting here can manipulate the sound of these units to tickle anyone's fancy making "sound" determinations extremely fickle.
     
  12. cc43fan

    cc43fan I'll sleep when I'm dead Subscriber

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    On a side note...where did you get the squirrel mugshot mug (2nd pic, next to cordless drill)?? My wife would love it!!
     
  13. dshoaf

    dshoaf That high voltage buzz Subscriber

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    For serious solder sucking, this is the device. Not cheap but highly effective!

    Cheers,

    David
     
  14. Rich Andrews

    Rich Andrews Well-Known Member

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    I see no mention of the Hakko being static safe.
     
  15. Rich Andrews

    Rich Andrews Well-Known Member

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    Location:
    TX
    MR67 Mod

    There is a published modification for the MR67 and other tuners. It involves placing a .0015 and a 27K ohm resistor in parallel from pin 8 of one 8BL8 to pin 8 of the other 6BL8. This is NOT a slap it in and go modification. The tuner must be adjusted for maximum separation after installation. For full details see Service Bulletin #114 in the document at http://rich.homeunix.com/McIntosh/servics_bulletins.pdf It does really improve the stereo imaging.
     
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  16. c_dk

    c_dk Addicted Member

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    Thanks for the good read.....have not reread those old 60s service bullitens in years. I find it most interesting the hand holding Mac is doing "warming " all the tube techs to solid state!
     
  17. jdwk

    jdwk AK Subscriber Subscriber

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    well I think the "mods" would be good for things like discontinued parts ( I guess that would fall under "replacements" not mods) but thats sort of what we would need to have done. Need to keep those audio classics running.
     
  18. jlovda

    jlovda Things I loved from the 60's and 70's

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    A little story about non-documented mods...

    When I was a senior in college in 1968 (I was an EE student at the U of Ill), I had a summer job at Stewart-Warner Electronics in Chicago aligning modules used in APN-159 radar altimeters used in F-4 Phantom jets in Viet Nam. There were four techs who did most of the final tests and alignments and they knew the units inside and out. Every once and a great while a unit would come on their bench that would not fall in spec for one parameter no matter how much tweaking was attempted. They did know from experience that if they changed one resistor from X ohms to Y ohms it would pass.

    The unit would go in the field and work fine for many months until a random component would fail. A military tech would go through the unit and find the bad component but then....comparing the schematic to the unit see that one resistor was incorrect. Feeling like a crime solving detective, he would change the resistor back to the value shown in the schematic. Before it could be returned to service the unit had to pass the complete list of tests. Guess what, the unit would never fall in spec for one of the parameters and had to get sent back to the states for higher level testing at the factory. :nono:
     
    Last edited: Oct 30, 2012
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  19. chinacave

    chinacave Its Like a Jungle Sometimes; It makes me Wonder Subscriber

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    I have that same Mug!

    A relic of the epic 2004 Christmas Battle of Ludlow Vt with the chase of a flying squirrel at a ski-house we stayed at. My Sister-in Law called the local cops to chase down the varmint, we caught it and tossed it outside before they could muster the SWAT team.

    Many gag gifts were bought, the joke wore thin quickly, so I never gave them the mug.
     
  20. dewickt

    dewickt Will fix about Anything

    Messages:
    3,389
    Location:
    Knoxville, TN
    Got to have an appropriate mug for the bench, just like a good temperature controlled iron, and a Variac.
     

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