Another M-80 Restoration Project

Discussion in 'Yamaha' started by DeltaB, Aug 2, 2018.

  1. DeltaB

    DeltaB New Member

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    Purchased a M-80, which was advertised as "mint in the box" (you know how those go) and knowing it would arrive with at least some work needing to be performed, I weighed the cost vs. return and knew what I was getting into. It did arrive with damage from being dropped by FedEx, smashing all the speaker output terminals, however, knowing that at some point I would replace them it wasn't as sorrowful as it sounds.

    This unit however, does exhibit signs of very low hours usage and all in all, is a very fine candidate for restoration. Since parts will be arriving tomorrow, in the coming days I'll post pics of the project as it progresses this weekend. As it appears, besides the rear terminal replace, this will only require a recap and cleanup.
     
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  2. milo63

    milo63 AK Subscriber Subscriber

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    Are you doing DIY posts or one of those fancy prebuilt units?

    Looking forward to the show. I should recap my M-60 but it's "aesthetically challenged" so I'll probably just enjoy it.
     
    Last edited: Aug 6, 2018
  3. DeltaB

    DeltaB New Member

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    Back in the 80's and 90's I was at Altec-Lansing. I do actually love doing all my work myself. I'll be posting some pics and write-up in the coming days...
     
  4. avionic

    avionic " Black Knights " Subscriber

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    There are four TO-220 transistors on the two APU boards that you will need to reflow the solder on. There is always 1 or 2 of them that have annular ring cracks around the leads. I would have a good look at the TO-92's as well.

    All the TO-126 transistors on the main board also will need to be reflowed.
    The M-85 service manual is more accurate than the M-80 service manual.
    The only difference between the two amplifiers is whats written on the front and rear panel.
     
    Last edited: Aug 6, 2018
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  5. DeltaB

    DeltaB New Member

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    Thanks for the heads-up Avionic. Like I stated before, I was at Altec-Lansing for many years. This unit spent most of its life in the box, and has very few hours on it, in fact, none of the joints have experienced enough thermal cycles to reflow. I always go meticulously over a device before placing it into service. Kester 44 is our friend. :)
     
  6. avionic

    avionic " Black Knights " Subscriber

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    It still has the glue issues to clean up.Sounds like it will be a breeze for sure.
     

     

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  7. DeltaB

    DeltaB New Member

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    It didn't even get plugged into the Variac until it was disassembled, inspected and DBSG removed, and the components placed back in. I never reflow a joint. Always use a soldapult to remove the old solder, and rejoin with new joint. Seeing thousand upon thousand of amps coming out of the burn rack at Altec will show you one thing, never reflow a joint, and solid solder joints is what makes for low IMD/THD. I already had made the decisions on the caps and Mouser was kind enough to exchange copius amounts of my cash for their parts delivered on Friday.

    The DBSG was still tan throughout, and only a very small section smaller than your pinky fingernail over the bus bar had begun to start to brown. No passive devices were damaged at all. No oxidation on any of the leads in this unit actually. Only a trace of corrosion around the edge where the DBSG touched the bus bar, and it didn't even eat through any of the copper.
     
    Last edited: Aug 6, 2018
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  8. avionic

    avionic " Black Knights " Subscriber

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    Sweet..
     
  9. DeltaB

    DeltaB New Member

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    You know Avionic, when you come across an ad over on ebay, and the guy is claiming "mint in box" you grin and say to yourself, "is this guy's definition of "mint" the same as mine or does it smell like candy..." It's nice to come across a treasure like this, I paid premium for it, but nice none the less. I'll take time to gather up pics and some tips from my experience after a little more listening time...
     
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  10. avionic

    avionic " Black Knights " Subscriber

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  11. OMGCat!

    OMGCat! AK Subscriber Subscriber

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    I've had a few of the same amps over time and some have been just fine with the glue being pliable and all of the leads still shiny while others have been a corroded mess.

    The only difference that I can see is the amps that seem to have more use tend to have much cruddier looking glue. Maybe it's thermal cycling that dries the glue out and has it turn into creeping death.
     

     

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  12. avionic

    avionic " Black Knights " Subscriber

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    Did you know that the multi-voltage model M-80 has clear anodized heatsinks and the 120v only model has black anodized heatsinks. Not entirely sure if that holds true with the 85.
     
  13. DeltaB

    DeltaB New Member

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    Yeah, the U model (US) had the black versions. Mine is a R model. (general worldwide)
     
  14. avionic

    avionic " Black Knights " Subscriber

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    DSC04204.JPG I picked up a cosmetically mint (u), including the binding posts:thumbsup:, non-working that was fixed by resoldering the TO-126's One was totally isolated from the circuit. It also had a little glue/oxidation action going on. The cost was less than a pack of smokes.
    Its one of my daily drivers. Driving NS-1000's
     
    Last edited: Aug 6, 2018
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  15. DeltaB

    DeltaB New Member

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    As this last week has been busy with work, I've had little time to expound on some of the restoration experiences. Listening test are going well, and here is some selections for the first round of issues to deal with in bringing a 30 year old amp back to original glory. As with all older equipment, general solder condition and Al caps are the first places to spend some quality time.

    The power boards were fitted with Nichicon UPM1H101MPD6 105 degree low impedance 5000hr 100uf 50v.

    The remainder of the Al caps, except for the 1000uf 100v, were replaced with matching value ELNA SilMic II for their sound quality.

    Nichcon LKG Type II "Gold Tune" Snap-In 1000uf 100v LKG2A102MESABK were specifically chosen for a couple of reasons. And while many like to use the UFW or UKW in their change, they don't realize that this amp can draw more than the rated current for Fine Golds at the same capacitance and voltage. (over 2 amps each side) When you exceed the ripple current rating, you will overheat the core of the cap, and shorten it's life greatly, and starve the circuit when it needs it most. Careful selection is required when you start addressing some of the basic requirements to keep a circuit well fed. Derating a cap of greater voltage will also run you into other issues from a design perspective that would require more time to explain than I am going to spend in this post.

    The next round is going to include removing the original Mylar's and bringing WIMA's to the mix.

    Happy listening weekend folks!
     
    Last edited: Aug 11, 2018 at 2:14 PM

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