1. Time for some upgrades in server hardware and software to enhance security and take AK to the next level. Please contribute what you can to sales@audiokarma.org at PayPal.com - Thanks from the AK Team
    Dismiss Notice

Marantz 250M rebuild by Bob Speece

Discussion in 'Marantz Audio' started by airtime, Mar 22, 2017.

  1. airtime

    airtime Super Member

    Messages:
    2,181
    Location:
    Central Arizona
    I wanted to post this for a while now. Bob did an amazing job on this jewel of an amp. And BTW it sounds every bit as good as my coveted Latino ST-70 tube amp.

    If I miss a step I hope Bob jumps in and adds to it.

    First old caps out and heat sinks removed
    Marant 250 caps and resistor.jpg

    All the old heatsink compound and mica insulators removed and heatsinks cleaned up...
    Marantz 250 heat sinks.jpg

    Newmain filter caps on the left with the old original caps on the right
    Marantz 250 filter caps.jpg

    Over the last several days I have finished the relay protection board and the left amp board.
    Before....
    Marantz 250 amp board after.jpg

    After
    Marantz 250 amp board after.jpg Marantz 250 amp board after.jpg

    This is a list of some of the things Bob did as well.

    I replaced the drivers with new correctly matched 2SC783 and 2SA483's with new mica insulators and Dow 340 heatsink compound making sure that the small nylon spacers were in place.

    I replaced the predrivers with new matched ST 2N3440 and 2N5416's.

    I replaced the differential input pair with matched and heatshrink bonded MPS6519's.

    Used Vishay AML138 for the axial caps and a Panasonic FC for the 100uf tantalum C527.


    Tomorrow I plan on working on the right channel amp board with the same treatment.

    Those oem original type Toshiba TO66 and ST 3440/5416 transistors are rare and hard to source but they are the best and look far better than shoehorning in some TO220's like others do.


    pics of the flyback diodes mod that is detailed in Service Bulletin M-250-3.
    Marantz 250 diode.jpg

    I have the new OnSemi MJE21195/96 output transistors installed on their heatsinks with new mica insulators and Dow 340 heatsink compound.
    marantz 250 on semi.jpg

    Both new 24,000uf 100v main filter caps are in ,along with their Panasonic 2.2uf poly film bypass caps....
    Marantz  250 filter caps and polys.jpg

    New LED lamps using Don Haywood's premium lamps.....
    Marantz 250 LED.jpg
     

     

    Please register to disable this ad.

  2. mcheinstein

    mcheinstein New Member

    Messages:
    16
    Looks beautiful, Airtime. Thanks again for helping me out in my thread on the 1200. I'll be following this one!
     
    KutzlerTrans likes this.
  3. KutzlerTrans

    KutzlerTrans Jennie & I with Buddy and Barney. Subscriber

    Messages:
    2,990
    Location:
    Wisconsin
    Mr Bob is one of the Best :thumbsup:
    Congrats on the unit. Now you can blow the doors off of the place.:jump:
     
  4. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
    2,913
    Location:
    N. Richland Hills, TX
    Fantastic looking unit! I'm sure Bob has that thing ready to crank it up for many years to come. :thumbsup:
     
  5. airtime

    airtime Super Member

    Messages:
    2,181
    Location:
    Central Arizona
    I didn't want to get into an audio review as much as point out the detail that Bob did restoring this beauty.

    However sonically speaking it's awesome sounding. Honestly I wasn't expecting it to sound as good as it does. Now I look forward to using it in the rotation even against my tube amps.
     
    catrafter, SWL3600 and Trojan4Life like this.
  6. SWL3600

    SWL3600 Super Member

    Messages:
    1,512
    Location:
    Twin Lakes, WI
    Awesome. I'm looking forward to Bob restoring my 250 this fall. Can't wait! :)
     

     

    Please register to disable this ad.

  7. audiobeer

    audiobeer AK Subscriber Subscriber

    Messages:
    572
    Location:
    St. Peters, Mo.
    I wish I had room to list all the items Bob has restored for me. He’s rebuilding my Marantz 4400 and has a 250M and 33 Preamp he’s getting together for me. He’s “The Man” when it comes to Vintage equipment!
     
    SWL3600 likes this.
  8. Steven Tate

    Steven Tate AK Subscriber Subscriber

    Messages:
    2,913
    Location:
    N. Richland Hills, TX
    Agree 100% :thumbsup:
     
  9. txturbo

    txturbo AK Subscriber Subscriber

    Messages:
    922
    Location:
    Austin, TX
    Really nice! I am a sucker for the blue PCB's.
     
  10. airtime

    airtime Super Member

    Messages:
    2,181
    Location:
    Central Arizona
    I'm listening to it RIGHT NOW. It's STILL a wow feeling when I turn it on
     
    SWL3600 likes this.
  11. airtime

    airtime Super Member

    Messages:
    2,181
    Location:
    Central Arizona
    For years I've been trying to like my NAD C275BEE power amp. But every time I plug it in and go back to the 250M I relearn what a jewel the 250M is. So once again the NAD will sit in the closet for another few years

    This NAD amp is about 8 years old and has less than 200 hours on it. Why use it when I the 250, VTA ST-70 and Sherwood.
     

     

    Please register to disable this ad.

  12. SWL3600

    SWL3600 Super Member

    Messages:
    1,512
    Location:
    Twin Lakes, WI
    Yer killin me....:)
     
  13. SWL3600

    SWL3600 Super Member

    Messages:
    1,512
    Location:
    Twin Lakes, WI
    Until my 250 goes to Bob for repair/restoration.....I've been using my restored 3300/1200b combo. I know the preamp in the 1200b is essentially a 3300 but after comparing both scenarios, for some reason using the separate 3300 pre sounds better.

    I'm anxious/curious to hear the difference in performance....if any....when I get the 250 back and compare it to the 1200b. In the meantime I absolutely dig the 1200b.
     
  14. airtime

    airtime Super Member

    Messages:
    2,181
    Location:
    Central Arizona
    The 3300 is a wonderful match for the 250.

    You're gonna be VERY happy with that 250 rebuild
     
    SWL3600 likes this.
  15. audiobeer

    audiobeer AK Subscriber Subscriber

    Messages:
    572
    Location:
    St. Peters, Mo.
    Well I got it back and works like a new one would. Anyone that says it is a sacrilege to make it black must know it’s easy to make it go back! Thanks again Bob Speece, I couldn’t be happier unless of course you delivered it with Beer and Pizza!
     

    Attached Files:

    SWL3600, Steven Tate, Bkphoto and 2 others like this.
  16. JediDude

    JediDude Active Member

    Messages:
    167
    Location:
    Ottawa, Ontario

    Looks good.... ;-})>
     

     

    Please register to disable this ad.

  17. Bkphoto

    Bkphoto Super Member

    Messages:
    1,761
    Location:
    Westchester, NY
    He did mine also...!
     
  18. Pete B

    Pete B AK Member Subscriber

    Messages:
    1,965
    Location:
    CT, USA
    Those new PSU caps look like, but I have to check the dimensions to be sure:
    Cornell-Dubilier DCM243U100DC2B

    I have one of these that needs a recap.
     
  19. airtime

    airtime Super Member

    Messages:
    2,181
    Location:
    Central Arizona
    Contact Bob for the exact part number.

    As I've already posted it sounds AMAZING
     
  20. wlhd1610

    wlhd1610 Penny and her new friend Sponsor Subscriber

    Messages:
    2,535
    Location:
    Catskill NY
    Thanks for all the kind words guys.

    This is the cap I use:
    DigiKey 565-3679-ND

    24,000uf 100V screw terminal fits perfectly in existing brackets.


    Bob
     
    Finnetric and Pete B like this.

Share This Page