McIntosh 1900 Recap and Restore

Discussion in 'McIntosh Audio' started by CohibaJoe, Jul 24, 2012.

  1. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Just got in my 2nd 1900 (Unit is Very Clean). I sent the 1st 1900 last week to Terry for a Complete restore.

    This one is a Fleebay BIN buy...$275...Was stored 15yrs...Spoke to seller and unit turns on, Lights up, FM/AM tuning moves but no sound.

    Before I diag. this...I have been looking for a recap list and only found one here.
    From w1jim...http://mail.audiokarma.net/forums/showthread.php?t=288200

    Since I am in NJ..For the Alignment I will be using Electronic Service Lab, Trenton, NJ

    These guy had been a Mac Service Center from the 70's - 90's. Just got back a Luxman M-120A Amp and what a Sweet Amp!!!!
     

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  2. aardvarcus

    aardvarcus New Member

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    The main speaker button is shown in the attached pircture as being in the "Mute" postion. I don't know if you un-muted it in your testing or used other speaker terminals, but if not that could be the reason. If that does not fix it, I would suggest working through all the speaker channel selections a few times in case one of them was corroded. You can also pull the preamp to amp jumpers and connect the amp and preamp sections to other equipment using the RCA jacks to diagnose which part you are having the issue with.
     
  3. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Thanks...I have removed some of the boards...The connections do need cleaning..I will complete this tonight and Power Up the system...Muting Off.

    Still looking for a Cap List...I am starting one and will post..I see the Service Manual that is here...The Serial # does match the book...Some of the Caps are not Posted in the SM? Maybe missed or changed?
     
  4. c_dk

    c_dk Addicted Member

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    There are a number of schematics for this long lived product....
     
  5. aardvarcus

    aardvarcus New Member

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    Cleaning the connections will make a huge difference in the sound of the amp (assuming they were corroded). I use deoxit contact cleaner. Be sure and clean the connections in the pushbuttons for the speaker selector switches (the straw on the deoxit can makes this easier) as well as the contacts to the boards, pull and clean the jumper, RCA plugs, slide switches, etcetera.

    I recently cleaned a 1900 for a friend who had lived in a house with major humidity/dampness issues. The amp had static and channels would cut in and out. A couple hours and a bottle of deoxit later it is as good as new. He will not stop talking about how much better it sounds. I noticed a mild improvement when I cleaned my family's fleet of 1900s, which had less corrosion.
     
  6. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    OK...Here comes the questions....

    Looking over and noticed this..Pic 2

    Not sure if the Cap is leaking? Speaking of the Big Cans.

    Has anyone replaced these? If so to what Brand and Value.

    Also, the Non-Inductive Resistors. I would like to replace with some Audio
    Resistors...

    Part Express has Dayton & Mills also Parts Connexion with Mills and other with more values.
    http://www.parts-express.com/non-inductive-resistor-index.cfm

    220 / 5w
    1500 / 5w
    (2) 3600 / 10w
    600 / 5w
    300 / 5w
    .33 / 5w
     

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  7. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Preamp Boards are done. Power Supply board cap is done. Need to order the Mills Non-Inductive Resistors.

    Preamp Boards L/R:
    (4) 100uf 16v to 100uf 25v Elna Silmic II
    (4) 10uf 63v to 10uf 100v Elna Silmic II

    Power Board:
    (1) 100uf 40v to 100uf 50v Elna Silmic II
     

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  8. c_dk

    c_dk Addicted Member

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    If I remember correctly...the .33 (and .56) wirewounds as used in the early 70s units were inductive....the change came with the switch to 188/189 outputs and a coresponding circuit change to control ocsilation in the MC2125 and MC2205 etc.
     
  9. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Hum...Let me contact Terry to make sure before I order..I have sent another 1900 for him for a rebuilt.
     
  10. c_dk

    c_dk Addicted Member

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    To my memory the non inductive/ inductive issue was only with the .15 ohm resistor...
     
  11. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Sent a message to Terry for info.

    I am going to also replace the Resistors with:
    Precsion Resistive Products (GP)9372 audio series 1/2 watt

    PreAmp Board
    Power Supply Board
    Channel Power Output Board
    IF & MPX Board
    AM Board

    At this rate...Maybe all.
     

     

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  12. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Did get the ?'s answered from Terry (Thank You!!!)

    On the Non-Inductive Resistors...If they are it was mesured Very Low(VHF RF region). I am going to replace with the Mills.

    The Cap I thought was leaky...seems to be extra Flux..(That's why I have asked the ?...as I am also learning, which is a Good Thing).

    Still going over the Resistors..I intend to replace them all.

    Once I get this done I will create a Excel file with the Caps and Resistors for each board.
     
  13. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Just completed the Resistor list.

    Going to put a order in with Mouser and PartsConnexion tonight.

    Stay Tune.....
     
  14. dshoaf

    dshoaf That high voltage buzz Subscriber

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    Would not suggest you try to do the I/F and FM Mpx boards with new resistors - unless of course you're planning on doing an FM alignment afterwards.

    Otherwise, you've got quite the project going there! Thanks for documenting it for us, too.

    Cheers,

    David
     
  15. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    I plan on taking this to my Service shop for a Full alignment.

    1st replace all the Caps and Tantalum...Test for a Day
    2nd replace Non-Inductive Resistors...Test for another Day
    3rd replace Resistors 1st on Power Supply, Pre-Amp & Power Outout...Test for a Day
    4th replace Resistors on IF & MPX and AM....Test for a Day
    5th replace all other Resistors....Test for a Day

    Then I will take this in for a Full Alignment.

    Pictures on each Board with be taken...
     
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  16. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Parts are on it's way. Will have these by the weekend.

    Pics will follow with each step.
     

     

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  17. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    OK...Got some parts in.

    Replaced the Caps..Left the AM & FM board alone at this time. The Elna Silmic II need around 20-25hrs to give me a look into the sound..80-100hr for Full Break-in.

    I do noticed the Selector Switches need more cleaning. Some I need to press in and wiggle for both speakers to have sound. Seems to me "Cost" cutting.

    Overall sound is Laid Back with Neutral Base/Treble Tone, Yet has Power to Throw in your Face. At this time it is Nice.

    Will this move the Sony STR-GX10ES out from Main Rotation...No...Not in your Dreams. But, it will get it's own spot as with just a Cap upgrade it does sound Very Nice.

    I get the Resistors in Monday. Will post some pics later.
     
    Last edited: Aug 9, 2012
  18. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    I am looking to replace the lamps. FleeBay(BlackSwapAudio) has a 1900 Kit...But I going to see if (QUA-CO AUDIO) can put together LED's.

    1st...The MAC engineers DO NOT get any Love from me. Not very thought out for getting into these lamps. Also looking at the Dial...If you have to restring this...Ouch.

    Maybe to keep the Service folks employed.

    I needed to get access to Top Switches..Speakers were cutting out. Deoxit the BLEEP out of them.

    Will have the resistors in Monday...Fun Fun
     

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    Last edited: Aug 10, 2012
  19. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Has anyone replaced the Big Can Caps?

    Looking to replace these.

    I am looking to get More Define Sound as at this time the 1900 can use More definition in the instruments.
     
  20. CohibaJoe

    CohibaJoe AK Subscriber Subscriber

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    Recapped the IF & MPX Board

    Well Well...That's better...Cleaner sound.

    Getting Better...Let's see how much more.
     

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