Shorted KA-7100 output TR

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by cwh, Jun 4, 2017.

  1. cwh

    cwh AK Subscriber Subscriber

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    What are current recommended subs for Qe27-30?

    My list includes:
    -MJ21193(4)G
    -MJ15022(3)G
    -KSC2690A, KSA1220A

    Carl
     
  2. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    Location:
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    Copied directly from my build list:

    Q27/28 2SD427 x2 > MJ21194 (NPN) output transistors if needed
    Q29/30 2SB557 x2 > MJ21193 (PNP) output transistors if needed
     
  3. cwh

    cwh AK Subscriber Subscriber

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    Thanks hopjohn! If you've got an updated list to share I'd happily take it.
     
  4. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    I can't share it unfortunately for reasons I cannot discuss. I'm sure others have their own if they'd like to provide it.
     
  5. cwh

    cwh AK Subscriber Subscriber

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    No worries, I do appreciate the thumbs up on the MJ21193.
     
  6. Dave47

    Dave47 New Member

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    2SD427s and 2SB557s seem to be readily available on ebay. Any reason you wish to substitute?
     
  7. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    Cus those and any others on eBay are likely fake. Why risk it? With good, genuine subs available.
     
  8. neevo

    neevo Well-Known Member

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    I have one with a few different options I can share from my build. Would be in 8 hours or so as going to bed now but when in office in the morning I can email if you send me your details. Excel file.
     
  9. Dave47

    Dave47 New Member

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    Is there a huge market for these? I know expensive components such as modern processors etc are copied but aren't these simply a niche market? Does it make anyone money to counterfeit these? Even if someone wanted to make counterfeits wouldn't be easier to simply buy some of the substitutes and simply re-mark them? If so then they are at least as good as the substitutes.

    I'm not sure I understand the market for counterfeiting these particular parts
     
    Last edited: Oct 10, 2017
  10. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    I don't understand it myself, but I can tell you I've seen currently produced transistors faked so it isn't reserved for obsolete parts. I doubt they'd bother with a legitimate sub when whatever is available to these people at the lowest cost is what they will use. As a general rule avoid ebay for any part related semiconductors where the source is unknown, especially if they are coming out of China.
     
  11. cwh

    cwh AK Subscriber Subscriber

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    Neevo, thanks I'll send a pm.
     
  12. neevo

    neevo Well-Known Member

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    542
    Location:
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    Looks like I can load up the document here, so lets give that a whirl!

    The list was built with inputs from a couple of awesome members on here (given hopjohns comments I will remove the names anyway as I am not sure if they have issues too) and I have 2 lists effectively which provides 2 options for each part (if a suitable option was available from Mouser).

    In the end I ordered everything (by mistake) so check the pivot carefully before you use that as an order form. The stuff I installed is listed in green and I can confirm my amp works perfectly and has been a pleasure to use since. There were a couple of upgrade parts in there too (eg the multi turn pots) which I highly recommend using too for anyone wanting to completely overhaul their KA-7100. In my rebuild thread I also upgraded the speaker connections too which is a great mod for those that are happy with a non standard amp.

    Edit: Didn't work uploading the excel document unfortunately, so I will upload a JPG and happy to email the excel to those that would like to play around with it (there is an option to load in pricing too).

    KA-7100 Restore List.jpg
     

    Attached Files:

    cwh likes this.
  13. Dave47

    Dave47 New Member

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    Thanks for posting this neevo. I have a KA-7100 that I'm trying to fix. Afterwards I might change some components to re-furbish it further.
     
  14. neevo

    neevo Well-Known Member

    Messages:
    542
    Location:
    Sydney, Australia
    Do it. They're not rare but I think they're one of the most gorgeous silver faces amps. Don't sound too bad either and they are built really well.

    I did a thread on my build, if I can do it, anyone can.
     
  15. 39cross

    39cross AK Subscriber Subscriber

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    It's a relatively easy amp to restore, but some disassembly is required to get to the tone control board and the eq board. in what is a rarity thus far in my experience, the underside of the main amp/ps board is printed with the component layout, so it's easy to ID the caps etc. you are replacing.
     
  16. hopjohn

    hopjohn Kenwood Krazy Subscriber

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    I've seen too many disasters to qualify that statement. Neevo had obvious, mechanically related skills (working on a lathe, tapping threads, just to name a few) that were beneficial in his rebuild. He sells himself short. If you suck at soldering (let's be honest some people do and it makes many of us cringe), practice first on some junk.
     
  17. 39cross

    39cross AK Subscriber Subscriber

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    I completely agree. I remember a thread here where someone really did a number on a KA-7100. It does require some mechanical aptitude and some practice. It's always easy when you know how (and even then sometimes it's not)!
     
  18. Dave47

    Dave47 New Member

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    Location:
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    I agree but I believe I do have the required mechanical and electrical aptitude and I have good soldering skills. I am an electrical engineer too - although that doesn't mean I am an expert on amplifiers and I most certainly will have questions and thus it is nice to know that some have worked on their 7100s. And it is nice to have the schematics too.

    I think my greatest skill however, is to know when I need to stop and research a bit before proceeding and to learn from other's experience.

    BTW neevo, I did glance at your thread and it is going to be a valuable resource. And you are right. It is a very nice looking amp.
     
  19. cwh

    cwh AK Subscriber Subscriber

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    Looks good Neevo and thanks for sharing.
     
  20. 39cross

    39cross AK Subscriber Subscriber

    Messages:
    831
    Location:
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    I don't think you'll have any problems!
    I helped Neevo with his list, which was based on the work of others here. I've restored two of them. Sold one to a friend who couldn't be happier with it. The other is currently doing duty in our kitchen area, hooked up to a pair of smaller Advents. It makes a great small-sized system with a big sound.
     

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