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MX-113 To Do's

Discussion in 'McIntosh Audio' started by jbailey930, Nov 6, 2018.

  1. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    859
    Location:
    N. Va
    Hi all - I have pre-owned MX-113 in my office setting paired with an MC2100 pushing little Neat Iota's. I bought the 113 from a local tech 5 years ago who said it was serviced. The 113 needs some cosmetic work and want to get support from the forum on a couple of tech issues. I've used the Testor touch up paint on the glass. It aint a beauty but its alright.....

    1. The signal strength meter doesn't work. It was working until 6 months ago or so. I've had the faceplate off to see if its obstructed. I don't want to go as far as removing the tuning wire tho. The light for the meter does work
    2. The red stereo indicator remains lit at all times - even while turning the dial and with no reception.
    3. There was a popping upon powering off and volume pot scratchiness. I had this at @Gregory 's place over the weekend. Did a look'see and cleaning. These symptoms are no longer present.

    Greg replaced a couple of caps on the AM and FM board per the service manual.
    Here are a couple of pics - the tech leaves the last time he was in the unit with his name/initials and date. [​IMG]

    [​IMG]
     

     

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  2. embrown057

    embrown057 Active Member

    Messages:
    182
    Location:
    Apollo Beach,FL
    Most I've worked on have had the same exact complaint. Power supply is the first you need to look at. Regulator go's bad and causes low or no voltage. Let's see a picture of the top side.
     
  3. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    859
    Location:
    N. Va
    thanks, Dr. Brown :)

    [​IMG]
    Previous work replaced this -
    [​IMG]

    [​IMG]
     
  4. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    859
    Location:
    N. Va
     

    Attached Files:

  5. embrown057

    embrown057 Active Member

    Messages:
    182
    Location:
    Apollo Beach,FL
    If that is one of those generic multi section caps he used I would scope that out and see how much ripple current you have. The 044-576 board has zener D 207 and pass transistor, need to replace them. Change Q202,203 and change all lytics in that circuit. Be carful at rework on these boards can be a challenge, don't lift any angular rings.
     
  6. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    859
    Location:
    N. Va
    Cap Parts List Order
    ------------------------------------------------------
    C204-A 200uF, 100V 220uF, 100V
    C204-B 200uF, 100V 220uF, 100V

    C210-A 150uF, 50V 220uF, 50V
    C210-B 300uF, 50V 330uF, 50V
    C210-C 50uF, 200V 47uF, 200V
    C210-D 200uF, 150V 220uF, 160V
     

     

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  7. embrown057

    embrown057 Active Member

    Messages:
    182
    Location:
    Apollo Beach,FL
    From your BOM is appears you going with multi contracted caps? Diodes, BJT's ? Need to get that power supply in good working.
     
  8. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    859
    Location:
    N. Va
    agreed. thanks for you advice.
     
  9. c_dk

    c_dk Addicted Member

    Messages:
    6,245
    Location:
    West Michigan
    The last new MX113 we got in was in 1978......so all these are at least 40 years old and well past their electrolytic cap replacement time. I would suspect most are over 45 years old.

    There are a number of tricks that have been developed by FM tuner techs to stabilize the performance of the FM tuners. Multiple tuner boards were used with schematic issues therefore showing up.

    FM issues should be addressed by a tech with the appropriate tuner test equipment and skill set.
     
  10. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    859
    Location:
    N. Va
    I am going to leave the tuner alone for now. Reception is pretty good 25 miles outside of DC using ribbon antenna.

    Let us know who in the greater DC area is an appropriate tech. I've used a couple and have not been pleased with the work. Given the age and condition its not worth to spend too much vs. buying a newer version.

    thanks
     
  11. c_dk

    c_dk Addicted Member

    Messages:
    6,245
    Location:
    West Michigan
    Well Myer Emco was the big deal in the DC area.......but John McQuire's people in Rockville were a fellow repack enabled dealer and also close to the company for beta products.
     

     

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  12. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    859
    Location:
    N. Va
    yeah, I bought most of my early hifi gear from Myer-Emco. They were great. Right next door in Falls Church was Washington Electronics who did repair work. Good old days.

    I met the owners from Just Audio at CAF last week but they are way up outside of Baltimore.......there are several EE's local and former Air Force comm techs that have the skills and equipment I know.
     
  13. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,721
    Location:
    Potomac Falls, Virginia
    Neither John or I really know if the multi-section cap was replaced, or just autographed in red marker by the tech. John says he's hearing 60 Hz hum in the speakers, and he's been looking around for a dual trace scope. Sounds to me like the multi-cap cans need to be re-stuffed. Have specified a list of Nich VR radials from Mouser (see list below). One photo of a re-stuffed multican has long slender brown 'lytics in place. What type are those?

    Code:
    MX-113  POWER SUPPLY CAP LIST   Multisection Cans
      Cap         Parts List           Nich VR          Size (mm)
    --------------------------------------------------------------
    C204-A        200uF, 100V        220uF, 100V       12.5 x 25
    C204-B        200uF, 100V        220uF, 100V       12.5 x 25
    
    C210-A        150uF, 50V         220uF, 50V          10 x 12.5
    C210-B        300uF, 50V         330uF, 50V          10 x 16
    C210-C         50uF, 200V         47uF, 200V       12.5 x 20
    C210-D        200uF, 150V        220uF, 160V         16 x 35.5
    

    Why replace the Zener? Is that component known to fail? I'd be willing to replace it, but cannot see changing transistors unless there's measured data to justify it.


    -Greg
     
    Last edited: Nov 17, 2018 at 2:04 PM
  14. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,721
    Location:
    Potomac Falls, Virginia
    There used to be a Myer-Emco just a few miles from here at 47010 Community Plaza in Sterling along Leesburg Pike. Was dismayed when they closed. Been in and out of Maryland for almost 40 years, lived there three times, and have had enough of that scene TYVM.

    -Greg
     

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