Pioneer SPEC-4 repair and restoration thread!

Discussion in 'Pioneer Audio' started by mattsd, Jun 10, 2012.

  1. laatsch55

    laatsch55 Super Member

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    Why the component between 7 and 9?
     
  2. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time

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    Hi Lee!!

    seven is unused foil, but I suspect that the foil is being used for relay coil power.

    the black band means a zero ohm resistor - or a jumper, really...

    it's just that the my2 pin out doesn't quite line up with the holes (at least the ways I tried it).
     
  3. laatsch55

    laatsch55 Super Member

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    Then we shall both learn something when the EW bestows upon us the rest of the pictorial epiphany.

    MTF, how ya doin Bud? Things getting back to normal yet??
     
  4. mattsd

    mattsd AK Subscriber Subscriber

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    Nice job, Glenn! I knew there had to be a cleaner way to do it, but I didn't have time to experiment with the first repair, so I had to do it the best way I could. I will be very interested in your thread.
     
  5. EchoWars

    EchoWars Hiding in Honduras

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    Yep. The board is wired for two completely separate relays. The top one would be activated by '7', and the bottom one by '9' (both share '8' as the return). But on the Molex connector, there's no wire connecting to '7', it is blank. I could have moved the wire in the connector from '9' to '7', but it's a bit of a battle to pop those wires out of those connectors. Easier to simply use a zero-ohm jumper between 9 and 7, and then I can leave the protection diode where it is (the larger MY2 almost covers up the component position for the top diode in its new 'forced-fit' position).
    Nope, it doesn't. Of course, the MY2 is so tall that it can ONLY go into the top position so it will clear the bottom chassis (and makes it by less than 3mm in any case). The NC pins get cut off, the top row of holes are enlarged in the proper direction to allow the top three pins to fit, and a whole new row of holes are drilled for the bottom row of pins. Then I drilled two more holes in the foil of '13' to make the jump over to '12'. Now the audio output line can be connected to either connector location at the bottom of the board, and the output is properly connected to '10', which is the meter signal line.

    The tricky part is fabricating what I call a 'solder dam' to engulf the pins in solder that are at the edge of the foil. I'll show this in more detail in the separate thread.
     
  6. laatsch55

    laatsch55 Super Member

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    Had to build a few of those solder dams. Clay works good.
     
  7. EchoWars

    EchoWars Hiding in Honduras

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    Nope. A wire, clipped from a resistor.
     
  8. laatsch55

    laatsch55 Super Member

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    Used as a capillary then? Man, I can chase those little hummers all over the board when Im using them to bridge traces.
     
  9. laatsch55

    laatsch55 Super Member

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    Rick Stout's Spec 4 turned out rather nice,....
     

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  10. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time

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    somebody's got some nice equipment... You Lee?

    I'm doing fine, but a bit tired lately as I am trying to break out of vampire hours (I used to sleep during the sun's appearance and was wide awake at the gawdawful hour of o dark hundred... Now I can't sleep past dawn - by sunrise I am irrevocably awake...

    and I'm trying to KEEP it that way - so, goodnight...^^^^^ :D
     
  11. laatsch55

    laatsch55 Super Member

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    Yes Mark, Those papers are the product of my Audio Precision ATS-1DD, audio test system. Simply delicious.... Goodnight Mark..
     
  12. laatsch55

    laatsch55 Super Member

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    It is sweet...
     

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  13. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time

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    I concur... :bigok:
     
  14. petervv

    petervv Member

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    guys,

    Finally found time to restore the basket case Spec-4 I bought 2 years ago.
    The amplifier boards were clearly from different batches as they had different components, one board did not even have the sleeves around strategic resistors. As both had a lot of burned parts I decided to remove (almost) all components and do a full rebuild.
    I selected most parts from the part lists and advices of MtF, EW and Mattsd, including the MY-02 relay swap EW-style.

    Everything worked first time right, bias and DC balance are rock stable and I get 2x180W into 8 Ohms without a problem. Power output into 4 Ohms is 390W, I tested this in burst mode to reduce dissipation in the amplifier, this translates into 10A. Following the manual the current limiter should be adjusted to 7A but the MJ21193/94 can handle more power than the originals so I took the risk for now. Anyone has an opinion?

    Some negative points:
    - the front has two deep and large scratches
    - I'm missing the rear 'bumpers
    - the housings of the two mains relays were broken into pieces, I glued them back together but I want to replace them in the end because I don't trust them, every now and then at least one of them makes a buzzing noise, haven't found what's wrong there.

    Thanks for the inspiration.

    regards, Peter
     
  15. petervv

    petervv Member

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    somehow the photo's didn't upload
     

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  16. laatsch55

    laatsch55 Super Member

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    Nice work, excellent slder skills!!
     
  17. VintagePlus

    VintagePlus Mcintosh and B&W

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    Awesome job!
     
  18. Oregonian

    Oregonian AK Subscriber Subscriber

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    You audio repair guys are amazing. Nothing short of it.
     
  19. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time

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    What happened with your relay to transformer clearances?

    I have a spec-4 that had the caps and relay rammed into the chassis/transformer...

    not many original parts left... :D
     
  20. laatsch55

    laatsch55 Super Member

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    No ceramics----EXCELLENT!
     

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