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Mint 2270 blowing fuse on power up.

Discussion in 'Marantz Audio' started by jd3rdcoast, Jun 3, 2018.

  1. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    167
    Location:
    Houston Area
    Hey all, I recently acquired a 2270 SN-11960 from someone who purchased several high end audio items at an estate sale. This 2270 is in the most pristine condition I have ever seen any 22xx unit to date. Like never seen the light of day inside and out. He said it was blowing main 3A fuse on power up. Today I am doing initial assessment.

    Nothing obvious internal, no burnt smell or components seen.

    1. Installed a new 3A fuse. No fuse was there.
    2. Removed Main/Pre jumpers. (Will this take Amp boards out of circuit?)
    3. DBT power up and yes there is a short somewhere.

    Suspect either Main Neg 9000k Capacitor as is very discolored bottom when compared to the Pos cap as seen in the pic below or Output Transistors.

    Curious which is quickest way to isolate which or both?
    1. Disconnect at Relay to caps?
    2. Pull amp boards to get at transistors? Not wanting to do any unnecessary molestation of this unit if possible.

    Thoughts?

    Here is pic if Main Caps: I have a set of 10k Gold Tunes if need them.
    upload_2018-6-3_10-48-3.jpeg

    upload_2018-6-3_10-54-34.jpeg
    upload_2018-6-3_10-55-51.jpeg
     

     

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  2. wlhd1610

    wlhd1610 Penny and her new friend Sponsor Subscriber

    Messages:
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    Relay not connected to caps it's for speaker protection.

    First ,build yourself a dim bulb tester- don't keep replacing fuses as a way to test.

    Fastest/easiest is to pull all four output transistors.

    See if dim bulb stays bright or dims down.

    If bright then you can isolate main caps but you'll need to snip or unsolder wiring to do that.

    Bob
     
  3. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    167
    Location:
    Houston Area
    Thanks Bob,

    Yes I have the DBT, it stays bright with 60w bulb on power up. Speaker switch not engaged.

    I misspoke when I said Rely to caps. I meant to say Bridge Rectifier feeding DC rail voltage to caps. I see removing Main In jumpers does not take the amp boards out because of rail voltage wires which are soldered to board.

    I’ll get after the output transistors.

    JD
     
  4. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    167
    Location:
    Houston Area
    Pulled the Outputs and sure enough both Right Channel outputs were shorted E-C. The Left side 2517 NPN-Hfe=57; 2518 PNP-Hfe=12
    Will order a full set of Outputs.

    Unit powers up with DBT and light goes dim with no inputs. So that looks pretty good that everything else is at least functional.

    So planning on what to replace and or upgraded.
    1. Set of Outputs for R side
    2. Should I go ahead and get the L side Outputs while their off as well?
    3. Proactive on the temp regulated bias transistor H760 and replace with recommended MJE243G.
    4. Since I have the 10K Nichicon Gold Tune mains handy, Thinking I might as well put them in but will see how it sounds first.
    5. Debating to go any further and just let this one run as is for a while or go ahead and do the Main caps, PS, Tone Amp, Amps and Phono. Boards with typical replacements. I like what Dingman did with this thread following LeeStereo's guidance. : http://www.audiokarma.org/forums/in...tly-caps-and-diodes-a-few-transistors.810608/
    I have done two 2245's like that so this should be piece of cake at this point if I decide to put in the time.
     
  5. wlhd1610

    wlhd1610 Penny and her new friend Sponsor Subscriber

    Messages:
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    Location:
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    You're on the right track.
    I would get it working first before you start changing other things out.
    Install the new outputs in the bad channel ,power up on dbt while checking bias and dc offset and see if it's good.

    Bob
     
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  6. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    167
    Location:
    Houston Area
    Good News! Replaced the bad Right Outputs with MJ21195G / MJ21196G (and the Left since I had them.) Didn't realize they are the same I had purchased for 2245 replacements and I had a extra set. I believe they were mentioned as a viable 2245 sub when the spec'd ones were not available and they worked just fine there.

    Power Supply was at 36V and set to 35V.
    DC offsets were at about 60mv and set to less than 5mv.
    Bias: Right side was 15mv set to 10mv no problem. Left side was also 15mv. Full counter clockwise gets down to 11.5mV.
    Relay kicks not problem.

    Ran my test track through my HD88's: Billy Gibbons and the BFG's Perfectamundo, Track 3, "Your What's Happenin', Baby" Note: If you haven't heard this CD it's a burner. Super punchy bass lines, dueling Hammond B3's and drum kits and of course The Rev. Willie G's killer distorted hot licks and gravel voice. On a good system it's a real treat.

    Unit sounds SWEEEEET! Full sound stage, Nothing missing or shaded. That's the good.

    The not so Bad but should get addressed :
    1. Probably should do the H760 Bias transistor update so get better range for that left channel rather than full counter clockwise.
    2. The Power Switch activates but power stays on at all times. It looks like it's wired properly looking at it. But the back yellow wire is shorted to the to front hot lines either internally or by the snubber capacitor. The back orange wire engages as it should.
    3. That's really it unless I want to take any proactive measures. This thing really looks as good as the day it came out the box internally and externally other than someone did a quality LED upgrade.
    4. Anything else I need to check? I have scope if needed.

    Power Switch. Should I pull the cap and check continuity again?
    2270-PwrSwitch.jpg
    I think this is a keeper. "Honey, it's important to keep a chain of continuity going! 2245, 2250B, 2270..."
    2270.jpg
     

     

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  7. wlhd1610

    wlhd1610 Penny and her new friend Sponsor Subscriber

    Messages:
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    You can get a new switch from Digikey for about $7 ,install a new snubber cap while you're in there.

    Bob
     
  8. rBuckner

    rBuckner Luv 2 Restore Subscriber

    Messages:
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    The 2270 uses a 4A fuse, hopefully you caught that already!
     
  9. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    167
    Location:
    Houston Area
    Yes, Thanks. I had 3's in hand and what is in there now while I finish up. Currently, searching forum to see if power switch is available on Mouser.
     
  10. willyrover

    willyrover Super Member

    Messages:
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    Anyone happen to have the Digikey item number for this switch?
     
  11. rBuckner

    rBuckner Luv 2 Restore Subscriber

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    DigiKey is EG1018

    Mouser is 612-P227EE2B20A
     

     

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  12. highvoltage_

    highvoltage_ Super Member

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    3,691
    Is a 2275 next?

    Glad to hear it's working. :)
     
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  13. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    167
    Location:
    Houston Area
    Thanks, I realized after that post to just go to Digikey for Mfg. # and cross ref. to Mouser. I prefer Mouser since in TX UPS ground is next day. Be here today!
     
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  14. willyrover

    willyrover Super Member

    Messages:
    3,120
    Location:
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    Thanks!
     
  15. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    167
    Location:
    Houston Area
    Here is the answer on why Power Switch stayed on.
    When opened found smoked and contact welded shut.
    upload_2018-6-7_12-20-52.jpeg
    C965B82A-DD9A-49AC-95B8-95A6F191E4CD.jpeg
     
    Last edited: Jun 7, 2018
  16. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
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    A lttle Deoxit ought to fix that right up. :naughty:
     
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  17. thxdave

    thxdave Lava Lamp repairman

    Messages:
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    Location:
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    .....yeah, it's a flesh wound....nothing more

    :)
     
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  18. catrafter

    catrafter Marantz Specialist Subscriber

    Messages:
    6,136
    Location:
    Montana
    No worries, the fuse should blow before your house burns down.:)

    Tom
     
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  19. jd3rdcoast

    jd3rdcoast AK Subscriber Subscriber

    Messages:
    167
    Location:
    Houston Area
    Replaced with new switch from Mouser. Had to shim inside between switch and panel with a small lock washer because the pushbutton mechanism arm bumps the inside panel when tighten the screws from front. The lockwashers keep that from happening. Original cap does not fit this smaller actuator so wrapped a bit of electrical tape around end and some rubber cement inside cap. While not as solid feel as original, seems to be holding. Anyone done other things to adapt original switch cap to new smaller actuator?.
     
  20. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
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    Location:
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    Teflon Tape works pretty good. There are vendors on the auction site that sell replacement caps with the smaller slot. They aren’t perfect for all silver face Marantz units, but they fit quite a few.
     

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