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Marantz 1090 - Is she too far gone?

Discussion in 'DIY' started by Hartin, Oct 1, 2018.

  1. Hartin

    Hartin New Member

    Messages:
    17
    Hi all, this is my first post to AK. I've found a great deal of information here this site has become invaluable to me. I've picked up a Marantz 1090 that i'd like to revive. its a good looking amp but after I opened it up i can see it needs some love.

    The unit power's on. Right channel puts out sound but doesn't seem stable (volume fluctuates). The left channel is completely out: fuse is blown as well as some components. (close up of components below)

    My question for you is how do we determine when a receiver is too far gone? I can solder and test components. I'm just not sure whether replacement parts are readily available or too costly. I know its hard to tell from a visual inspection. Just looking for some advice based on your past experience before I dive in too deep.
    20181001_105236.jpg 20181001_105312.jpg 20181001_105338.jpg 20181001_105400.jpg
     

     

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  2. BinaryMike

    BinaryMike Pelagic EE Subscriber

    There's a serious cosmetic problem with corrosion on the outside of the power transformer, but I don't see much difficulty beyond the usual tedium of restoration. I used to fix up components in similar condition routinely.
     
    Bruno Primas likes this.
  3. Blue Shadow

    Blue Shadow I gotta get me a new title

    Messages:
    21,473
    Location:
    SE PA
    Dang near pristine. Just an hour or two cleaning and derusting and that one with enough time drying and it would be ready for testing and repair as needed.

    Those with the experience and the service manual might be able to walk you through a repair. Obvious where to start after it is cleaned up with those burned up resistors. Locate them on the schematic and folks can suggest what else to look at as you go through the restoration process.
     
  4. blhagstrom

    blhagstrom Mad Scientist, fixer. Subscriber

    Messages:
    12,855
    Location:
    Duvall, Washington
    She's rough but she'll sing again.

    I've revived worse than that, true zombies.

    Given the amount of electronic damage, it could be a bit of work to resurrect.
    Original parts are all obsolete. We've determined a lot of suitable replacement parts.
     
  5. Hartin

    Hartin New Member

    Messages:
    17
    Thanks for the input guys! I'll start with the "Deep Cleaning" sticky and post updates. Any advice on cleaning up the transformer? I was going to light sand it, just not sure how sealed these things typically are. are there chemical options that dont require submersion?
     
  6. slimecity

    slimecity Super Member

    Messages:
    3,079
    Location:
    New Zealand
    Theres a thread here somewhere on a guy who found a sansui amplifier (cant remember the model number) buried in some dirt. It looked like it had been there for a while.

    He dug it out.

    He cleaned it up.

    And it worked!

    So yea - no issues here I reckon.

    You can alternatively have a unit that is in perfect cosmetic condition but it happens to have serious faults. You never know, this unit could work OK.

    I would however pay extra attention to switch, pot and other contacts when cleaning, as they would have been exposed to more dirt/rust etc than a similar unit that had been looked after a bit better
     
    Last edited: Oct 2, 2018
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  7. cademan

    cademan Addicted Member

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    9,047
    The right channel volume fluctuations could be dirty controls. Your left channel is another story. :yikes:

    A blown fuse, a few smoked resistors, maybe a pre driver or two, and the emitter resistors, all point to shorted output transistors in the left channel.

    You don't know how it was abused before you got a hold of it, but it reminds me of when someone who doesn't know what they are doing, wraps tin foil around a blown fuse and then the smoke comes out. :oops:

    A fuse wrapped in tin foil will do all that damage until a resistor or some other component finally breaks the circuit. :rolleyes:
     
  8. ChrisMarantz

    ChrisMarantz AK Subscriber Subscriber

    Messages:
    2,554
    Location:
    San Francisco Bay Area
    Some of the dirtiest and worst looking equipment I work on turn out to be the simplest and most straightforward electronic rebuilds I do - making them look new again takes more time. . .

    The 1090 is not my personal favorite Marantz Integrated Amplifier ever made - however that's just my personal bias

    There's a good rebuild / upgrade thread in the Marantz Forum by LeeStereo

    He does an excellent job working through some of the short comings of the 1090 - Chris
     
    Last edited: Oct 2, 2018
  9. Anti_Skate

    Anti_Skate AK Subscriber Subscriber

    Messages:
    552
    Location:
    Somewhere in Mid Michigan
    Looks like Fun to me.
     
  10. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Fort Dodge, Iowa
    Looks like someone has been in there before and replaced a few OEM resistors with junk carbon composite resistors in the " chernobyl'd" section of the amplifier circuit.
     
  11. drew_t

    drew_t AK Subscriber Subscriber

    Messages:
    702
    For now, I would just try to brush the loose rust off it, and not worry too much about what it looks like.
     

     

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  12. ChrisMarantz

    ChrisMarantz AK Subscriber Subscriber

    Messages:
    2,554
    Location:
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    I think you can remove the end caps fairly easily. You can use some Navel-Jelly on them to remove the rust, as well on the core laminations. A brass brush will help with removing the loose rust. If the covers are pitted - you can use some automotive Contour Glazing Putty to fill the pits and then prime and paint everything.

    I had a Model 250 with a similar transformer and it turned out very close to new when I was done - Chris.
     
  13. Hartin

    Hartin New Member

    Messages:
    17
    I've cleaned up one board and I think I see why it blew up. Previous repair looks lousy. Lots of old flux left behind, possibly bridged joints. Looks like Cademan and Avionic are right. left channel output transistors were part of the previous work.

    I'm going to start testing components and comparing to the service manual specs. I'm sure I'll need some help identifying replacements. Should I continue that here in the DIY board or move to the Marantz board?
     

    Attached Files:

  14. slimecity

    slimecity Super Member

    Messages:
    3,079
    Location:
    New Zealand
    Start by cleaning the flux off with say, an old toothbrush and some isopropyl alcohol - that really makes a difference to see what you are doing
     
  15. ChrisMarantz

    ChrisMarantz AK Subscriber Subscriber

    Messages:
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    Location:
    San Francisco Bay Area
    I looks like someone was soldering with a hot nail - Chris
     
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  16. ConradH

    ConradH Addicted Member

    Messages:
    7,959
    Location:
    Canandaigua, NY
    OT, but brings to mind instructions I saw in a scientific book for making tiny thermocouples or something- they suggested soldering them with a hot sewing needle! Wonder if they ever actually tried it?

    Non OT, those boards look pretty good. Clean up the flux, fix whatever's wrong and it should be good as new.
     
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  17. Hartin

    Hartin New Member

    Messages:
    17
    Working on the Main Amp PCB
    I dont have a good reference manual to work from so I'm looking for some validation of my replacements.
    ID Replacement Part (Digi-Key) Bands
    R759 CF14JT100RCT-ND Br Blk Br Gld
    R757 CF14JT100RCT-ND Br Blk Br Gld
    R721 CF14JT2K20CT-ND R R R Gld
    R751 CF14JT200RCT-ND R Blk Br Gld
    R745 CF14JT150RCT-ND Br Gr Br Gld
    R749 CF14JT200RCT-ND R Blk Br Gld
    These are the resistors from the left channel that are damaged or incorrect replacements from a previous repair (tolerances dont match the right channel)
    I have two questions.
    1. Is there a general consensus on replacing ceramic film with metallic film?
    2. If I were to replace with metallic film should all other ceramic film resistors be replaced as well?​
     

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  18. BinaryMike

    BinaryMike Pelagic EE Subscriber

    Your color bands match the values encoded in the part numbers.

    Carbon film is a generally acceptable replacement for carbon composition and carbon film originals. Metal film and metal oxide film offer a performance upgrade that's useful in some circuit positions. They're also more reliable, so some folks like to use 'em everywhere --- especially when there's little difference in cost.
     
  19. Mike Sweeney

    Mike Sweeney AK Subscriber Subscriber

    Messages:
    493
    Location:
    Orange CA
    The metal film resistors can impact tone. I use carbon as a rule but use metal when marantz used them. I also use flameproof resistors for the bigger load resistors. Just in case someone lets the magic smoke out ;) I also pull ans test the power transistors as a rule. Often they test good but low so they get replaced and ill keep them as emergency spares. You just don't know the history and how abused they were and replacements are cheap. I've heard that they are the marantz sound but I've never heard a difference. The caps make more of a difference in my ears.
     
  20. Hartin

    Hartin New Member

    Messages:
    17
    Here's the repaired main amp board. Had a little trouble with pads lifting in previously repaired areas but otherwise no issues.

    Im going to put it back together and see if it will fire up. Any tips? Should I try headphones first? Connect up to sacrificial speakers? Measure speaker output with a DMM?
     

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