MX-113 To Do's

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

  1. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    886
    Location:
    N. Va
    Yeah, the Mallory cap and bracket hold up the other side, but we can add a small L on the sub chassis.
     

     

    Please register to disable this ad.

  2. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,763
    Location:
    Potomac Falls, Virginia
    Ok fine and good idea, here's the situation.

    The MX113 Power Supply PCB (PS PCB) has two mounting brackets, one on the LEFT in photo below, and C204 (the Mallory can) on the RIGHT.

    mx113_PSPCB_Cap.jpg


    Close-up of bracket on LEFT side.

    mx113_PSPCB_bracket.jpg


    RIGHT side of MX113 PS PCB

    According to the schematic, there's a bracket hole in the lower-right corner of the PS PCB. Only a bracket, a couple screws and drill hole are needed.

    PCB_044576.jpg


    C204A and C204B, which John already has, can be soldered directly to the PCB.

    The other cap-can will be restuffed and potted, and that horrible red marker removed!


    -Greg
     
    jbailey930 likes this.
  3. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,763
    Location:
    Potomac Falls, Virginia
    Update on MX113.

    John had me over today to remove the can caps.. desolder C204 and cut wires on C210.

    C204 BEFORE pic..
    MX113_C204_before.jpg


    AFTER
    MX113_C204_pads.jpg

    Two of the cap lugs were bent over against the PCB (upper-left and lower right lugs, with the latter being the worst to remove).


    END view of C210.

    Notice clockwise from upper right, are TWO red wires, a red/white wire, a violet wire, and orange wire.
    MX113_C210_before.jpg


    The two caps removed..

    MX113_cans_removed.jpg

    C204 will be discarded and Nichicon radials soldered to PCB.

    C210 will be RESTUFFED with Nichicon radial caps potted in place.


    This is a simplified schematic of C210 A, B, C, D.

    C210_A-B-C-D_simple.png


    John will be gutting C210 can soon.


    -Greg
     
    Last edited: Feb 10, 2019
  4. c_dk

    c_dk Addicted Member

    Messages:
    6,508
    Location:
    West Michigan
    I would drill out the two rivets holding the c210 cap clamps and build a small circuit board with standoffs threaded into the rivet holes.

    Toss the old c210 away and save the mess and fuss for a non cosmetic cap. I would add some added high frequency filtering to the PS while redesigning it.
     
  5. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,763
    Location:
    Potomac Falls, Virginia
    Thank you but no sir. The plan is to stuff the can with Nichicon lytics, butt-solder existing wires with heatshrink, pot it with goop, and snap the can back into the clamps. Someone else can adulterate it with a hobby board.

    This will be a NEW experiment in restuffing Mc cans.


    -Greg
     
  6. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,763
    Location:
    Potomac Falls, Virginia
    A new L-bracket will be needed to secure the end of the MX113 PCB that was supported by C204 and its spring clamp.

    Back side of PCB

    L_bracket_backside.jpg


    Front side of PCB with sketch of L-bracket to chassis

    L_bracket_needed_enh.png
    Not to scale..

    A new clearance hole will be needed in the chassis.


    -Greg
     
    Last edited: Jan 29, 2019

     

    Please register to disable this ad.

  7. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    886
    Location:
    N. Va
    Good time with Greg pulling the old caps out today. The Sprague 066-128 was piece of cake. The Mallory was a pain due to how two of the spades were bent through the board. Took quite a bit of solder wick and patience.

    Our unfortunate news was the HP 1206a scope I got was not fully functional. Have to figure that out.
     
  8. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,763
    Location:
    Potomac Falls, Virginia

    Today's activities on the MX113 power supply restoration



    C204 replaced with Nichicon VR radial (solder side). No photo taken of component side apparently.

    MX113_C204_solders.jpg

    Notice original `spring clamp´ and new 220uF cap on top.


    C210 can preparation

    John took the advice of removing the `tab ring´ so the FOUR new caps could be inserted in a bundle, see below.

    MX113_can_prep.jpg



    Cap core assembled into a bundle and `tagged´ for joining to original wires

    MX113_C210_core.jpg

    All negative leads (white stripes) soldered around a center AWG 20 copper pigtail and dipstick.


    Cap bundle test-fitted inside can

    MX113_C210_core_in _can.jpg

    Caps are all in the lower half of the can with plenty of room to hide them


    Looks like it's going to come out great!


    -Greg
     
    Last edited: Feb 10, 2019
    jbailey930 likes this.
  9. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    886
    Location:
    N. Va
    @Gregory great work yesterday. The extra time put in thinking through the arrangement of the caps in the can was crucial to a clean install. We spent more "tech time" figuring out how to bundle and gang those together than what I have into the unit!

    Here's the other side of the board where the Mallory can was located

    IMG_3409.jpg and another from the board side. Notice the clean soldering. The can left large holes

    IMG_3408.jpg
     
  10. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    886
    Location:
    N. Va
    Ready to install the re-stuffed Sprague cap, but have a question. The Sprague cap was wrapped in plastic. I removed the plastic to clean out the material. Is the plastic necessary to ground the cap on the chassis separate from the ground lugs? Thanks
     
  11. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,763
    Location:
    Potomac Falls, Virginia
    The cap-can should be grounded because the Power Transformer RED/YEL wire was soldered to the can lug (see below, top of pic).

    close-up_c210.jpg

    At the bottom on can (just out of focus at bottom) is a can lug with a `snipped´ wire end. Below that is a solder lug riveted to the chassis (ground).


    Here's the MX113 PS schematic with GREEN lines drawn to represent `virtual´ RED/YEL transformer center-tap wire.

    MX113_PS_schematic.png


    All these lines need to be grounded. However C210 cap-can was insulated with a transparent plastic wrap or cover.

    Looks like someone CUT a ground wire or a ground lug...

    C210_brackets_wire.jpg

    and cocked the can bracket. (chop chop!):rflmao:


    -Greg
     
    Last edited: Feb 7, 2019

     

    Please register to disable this ad.

  12. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    886
    Location:
    N. Va
    Hmmm, ‘‘twas not you or I. This is why we do our own tech work....
     
  13. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,763
    Location:
    Potomac Falls, Virginia
    More progress today on the MS113 cap-can restuff.

    Got the wires soldered to the `cap cluster´ with heat shrink tubing today, but not after confusing the cap values. Had to check schematic THREE times until both John and I agreed everything was correct.


    The original wires soldered to caps with heat shrink over top. I forgot to bring over heat gun! Rrrr

    C210_wires_54.jpg



    Side view with `copper pigtail´ straightened, it becomes a `copper tail´ which will be attached to a ground post with a ring terminal.

    C210_wires_64.jpg



    This view with cap bundle, heat shrink on ground bundle (center), and ground post.

    C210_wires_68.jpg


    Soon the original can will be mounted back on the spring clamps and the cap cluster stuffed inside.


    -Greg
     
    Last edited: Feb 10, 2019
  14. jbailey930

    jbailey930 AK Member Subscriber

    Messages:
    886
    Location:
    N. Va
    Very good news....buttoned up for now. @Gregory will post pics and voltage measurements. Nevertheless, its dead quiet hooked back into MC2100 and Neat Iota speakers in my office. Smooth and crisp. Very good soundstage for mini system.

    Of course there is more to do.... @Longfellowe indicated the MPX lamp could be Q405/6 short. Measured the voltage expecting 40v but = 0. Not sure what kind of heat sink there. And the signal meter is caput.... IMG_3416.jpg
     
  15. Gregory

    Gregory Soundco Kid Subscriber

    Messages:
    2,763
    Location:
    Potomac Falls, Virginia
    Another 2-1/2 hrs over at JBs workshop.. which is the furnace room and toasty warm.


    Below are the four cap leads and the ground bundle with heat shrink applied.

    heat_shrink_on.jpg

    The copper tail is to the LEFT, and the power transformer center-tap wire (YELLOW stripes) was soldered to the GROUND bundle.

    Remembered to bring the heat gun today to `shrink the tubing´ on the C210 cap cluster.


    Here is the cap cluster test fitted into original C210 can (gutted).

    can_test_fit.jpg


    Next the can is reinstalled into the spring brackets and cap cluster gently stuffed inside.

    can_reinstalled.jpg

    Have to say I like the way it came out.


    The copper tail from the ground bundle is now connected to the transformer mounting study with a bare ring lug.

    PS_Ground.jpg


    All work was checked and double-checked for correctness.. and then power applied.

    idle_power.jpg

    16 watts idle power seems low compared to my MR77 which draws 40-45 watts.


    Voltage check of the primary power supply section looked GOOD.

    MX113_voltages.jpg


    John says he connected it to the system in his study and the hum/noise were GONE. I have an idea the PS ground wasn't right, and of course the old clunker cans needed to be replaced.

    How many hours do we have into it JB? 30? since last spring? One of these days we'll have to get a pizza. :thumbsup:


    -Greg
     
    Last edited: Feb 10, 2019

Share This Page