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Yamaha B-2 restoration journey

Discussion in 'Yamaha' started by Mr. Yamaha, Nov 16, 2016.

  1. Uncle Paul

    Uncle Paul AK Subscriber Subscriber

    Messages:
    1,559
    Location:
    Portland, OR
    As usual, very nice work! You are definitely inspiring changes in my own restoration efforts.

    As to how tight, here is the Sil-Pad thermal performance data sheet from Bergquist showing thermal effectiveness vs mounting pressure for it's products. How that translates to how much you tighten the mounting screws. I would assume that you would mount the same as with mica and grease - tight enough to give a reasonable amount of pressure and keeping the hardware from loosening but not so tight as to distort the transistor case.
    http://www.bergquistcompany.com/pdfs/techLibrary/Sil Pad Overview.pdf

    I am curious as to which silpad you are using - I was planning on a K10, but looking at those charts there may be some better options from a thermal perspective, though not sure if the difference is meaningful.
     
  2. Mr. Yamaha

    Mr. Yamaha With a hint of Kenwood Subscriber

    Messages:
    463
    Location:
    Haarlem, The Netherlands
    Thanks. The silpads I have are from Aavid Thermalloy: https://www.aavid.com/products/thermal-interface/thermalsil/53-03-2g

    They can be ordered at Mouser.

    My biggest problem at the moment is the power switch. Which is unrepairable. The solder legs were so brittle that at first during other works one leg broke off. So it was still usable for a Triac power switch upgrade. When I went on that journey today two other legs broke off like they were made of cookie crumbles. Then I tried to dismantle it in order to check whether I could make new legs myself and a few parts flew across the kitchen. Very unfortunate and most likely not my day today :no:

    I was even tearing down my CT-600 and CT-810 to see whether they had similair switches, but they are quite different and can't be mounted in the same frame holes as the original.

    So, I'm in desperate need of a power switch. Searched the net and the Bay, no luck so far...

    The brand is Petrick and type 285/5. They tend to be used in different brands of audio equipment in the 70'ies and even other Yamaha's. Mostly CR-X00 receivers. By the looks of it, very crappy switch. Can you imagine 230V going through that thing for almost 40 years? :crazy: I really think those switches were not made for 40 years +. My B-2 seems to have been used occasionally, but it has had a 'new' switch which was connected with thermoplastic connector blocks.

    [​IMG]
     
  3. Bratwurst7s

    Bratwurst7s In The Frying Pan Subscriber

    Messages:
    2,999
    Location:
    Munich, Germany
    I spent some years working in the sil-pad industry. Normally best practice is not to compress the sil-pad more than 20% of it's free air thickness. So as an overly thick example, if you had a 1mm thick pad you wouldn't want to compress it to less than 0.8mm thickness.

    More compression generally won't bring you any extra thermal benefits and will start to damage the material.

    Cheers,
    James
     
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  4. Uncle Paul

    Uncle Paul AK Subscriber Subscriber

    Messages:
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    Location:
    Portland, OR
    Eventually a switch will pop up either through eBay or a forum member with a parts unit. In the mean time I'd reinstall the switch for cosmetics and wire it as if the switch was on, then use a switched power strip to turn it on and off.
     
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  5. Mr. Yamaha

    Mr. Yamaha With a hint of Kenwood Subscriber

    Messages:
    463
    Location:
    Haarlem, The Netherlands
    Installed those gems today with new silpads :trebon:

    [​IMG] [​IMG]
     
  6. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
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    Location:
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    Sorry Mr Yamaha but you should use mica insultators on THIS kind of heatsink NOT silpads . Those heatsink did exist in 3 versions :
    -1) anodized black aluminium with no epoxy paint
    - 2) anodized black aluminium with black epoxy paint
    - 3) anodized black aluminium with blue epoxy paint
    Micas should be used in case 2 and 3
    Silpads may be used in type 1 and only this one
    Power disspation is critical and if you use the wrong insulator you play with your V-FET !
     
    Last edited: Feb 21, 2017
  7. Mr. Yamaha

    Mr. Yamaha With a hint of Kenwood Subscriber

    Messages:
    463
    Location:
    Haarlem, The Netherlands
    Thanks Clinic, but your advise does always seems to come afterwards :rflmao:

    Can you explain why this is not the right thermal insulator for this type of heatsink? It was advised by a very respectable B-2 restorer :naughty: Although I did not tell him that my heatsinks had a blue coating.

    Btw, the VFET's in my unit were originally greased without mica sheets. 100% the first time they were taken out.
     
    Last edited: Feb 21, 2017
  8. Uncle Paul

    Uncle Paul AK Subscriber Subscriber

    Messages:
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    Location:
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    Somewhere in this forum there is a thread that goes into the epoxy heat sins, and as I recall the blue epoxy acted as an insulator. Yamaha dropped the practice as it was non standard. Here is a thread that at least mentions the three types - blue epoxy, black epoxy, and no epoxy. http://audiokarma.org/forums/index.php?threads/b2.439559/page-5#post-8029847

    My second B-2 has blue epoxy, but it will be a while before I start work on it. I will use an insulator if one is already present. Adding an insulator if it isn't needed lowers power dissipation needlessly.
     
  9. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
    988
    Location:
    Middle of Crook County
    Second that!
    Why use insulators on the blue (painted) heatsinks?
     
  10. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
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    Patrice, would you please elaborate on the need to use pads with the blue epoxy heatsinks?
     
  11. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,538
    Location:
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    Why use insulators on the blue and black (painted) heatsinks ?
    Yamaha did not with painted heatsink ! it is not necessary and we all understand why !
    Using insulators is necessary with no painted heatsink
    I have refixed many B2 and some were touched by somebody before who over tight TO3 screws ! this way the insulator paint was dammaged and an insulator was necessary to avoid short but only in this case .
    Using silpads is find if it is on recent heatsink with high precision place machined with high tolerances . Silpad should not be use on old heatsinks just because surface shape is critical .
    For a good thermal conductivity less space you have better it is . Multiple insulator is not good idea (paint + insulator ) decrease efficiency
    Am I clear ?
    PS : regarding : Thanks Clinic, but your advise does always seems to come afterwards , sorry I don't live in front of my computer ..I have customers waiting for repair
     
  12. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,538
    Location:
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    Now some pictures
    1) not painted heatsink
    2) blue painted heatsink with marks closer to screws area

    DSC05726-R.JPG DSC08191-R.JPG DSC08198-R.JPG DSC08782-R.JPG
    3) Dammaged area are easy to see on this black painted heatsink DSC05726-R.JPG DSC08191-R.JPG DSC08198-R.JPG DSC08782-R.JPG
     
  13. Mr. Yamaha

    Mr. Yamaha With a hint of Kenwood Subscriber

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    Location:
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    So no mica plates like you stated earlier, but just thermal grease?

    The blue paint of my heatsinks have no marks or damaged areas.
     
  14. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
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    Location:
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    If so , you don't need micas just specific grease (thermal grease)
     
  15. rottalpha

    rottalpha Yamaholic Subscriber

    Messages:
    988
    Location:
    Middle of Crook County
    Thank you for clarifying!
     
  16. Mr. Yamaha

    Mr. Yamaha With a hint of Kenwood Subscriber

    Messages:
    463
    Location:
    Haarlem, The Netherlands
    Great, I ordered some tooth paste :bigok:
     
  17. Mr. Yamaha

    Mr. Yamaha With a hint of Kenwood Subscriber

    Messages:
    463
    Location:
    Haarlem, The Netherlands
    Not sure whether anybody struggled with the mirrored PCB lay-out drawings in the SM, but I did. And I think it can make you make mistakes.

    So, I used my MS Paint skills to re-mirror the drawings and re-re-mirrored the component labels (not jumpers) afterwards to make it readable.

    Use at own risk! :biggrin:

    [​IMG]
     
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  18. belgianbrain

    belgianbrain AK Subscriber Subscriber

    Messages:
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    Location:
    Greater Toronto Area, Canada
    This would've been great to have a week ago!

    That is an annoying aspect of the service manual.

    But this amp is so easy to work on.
     
  19. Oilmaster

    Oilmaster Ozzy Subscriber

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    Location:
    Paris & The Hague
    ATTENTION: Yamaha has wrongly printed the TR110 symbol: emitter and collector are swapped. The EBC orientation is to be the same as TR107/108/109 !
     
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  20. Mr. Yamaha

    Mr. Yamaha With a hint of Kenwood Subscriber

    Messages:
    463
    Location:
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    Thanks for the tip. I use this scheme for orientation only. For pin-outs I only trust my component tester :naughty:
     
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