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schematic for Pioneer SA-510

Discussion in 'Datasheets, Manuals or Parts' started by niq_ro, Feb 10, 2004.

  1. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    That's not the same circuit as in post #17, which I was referring to. The #17 circuit uses a Vbe multiplier, the circuit you posted uses a crappy special diode (D3)
    , and is EXTREMELY dependent on the exact components being fitted supplied from Pioneer.

    I would suggest making sure R59 is shorted out, and also try shorting out R61 - this will reduce the bias to the minimum possible with D3 fitted.

    Personally I'd throw out D3 and fit a Vbe multiplier (with a preset resistor for setting it), then you can set it for whatever transistors you fit.

    No, it failed because the bias was too high - thermal runaway occurs VERY quickly.
     
  2. unclejed613

    unclejed613 Well-Known Member

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    always clean off the old thermal grease (alcohol is a good solvent for it) and put fresh grease on, and replace the mica insulators if the originals are damaged in any way,
    those STV diode stacks were very unreliable, and were prone to failing open circuit,
    more modern amps do away with the STV-3 diode stack and the other diode and resistor, and replace it with an adjustable bias circuit like the one shown below. the transistor should be mounted on the heat sink between the output transistors, and also coupled to the heatsink with thermal grease.
     
    Last edited: Apr 21, 2012
  3. Manuel Moreno

    Manuel Moreno New Member

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    I need the SA-508 service manual. And need to buy the same transistor: B773A and D883A. Can you tell me where ?
    email mmorenoc@hotmail.com
     
  4. dave

    Dave New Member

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  5. boinaverde

    boinaverde New Member

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    you find this schematic in hi-fi engine.and transistors is very true 2SD883A IS A NPN and 2SA773A IS A PNP.
     
  6. unclejed613

    unclejed613 Well-Known Member

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    i don't think you'll find the transistors. if you do find some, it's likely they're some other device that's been relabeled. they were discontinued many years ago, but there may be a legitimately licensed manufacturer making replacements.

    the japanese transistor cross reference lists 2SA1061 and 2SC2485 as replacements. since they are TO-3P packages instead of TO-3 metal packages, you have to bend the B and E leads to go into the socket, and wire a ring lug to the collector lead and put the ring lead on the mounting screw. otherwise, the TO-3P package should fit where the original metal package went. you may need a longer collector screw because the plastic package is a bit thicker than the original metal tab.. you ill also need a rectangular heat sink insulator instead of the oval one.
     
  7. Rotarymaker

    Rotarymaker New Member

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    An old "trick of the electronics trade" was to place a 2200uF to 4700uF capacitor in series with each speaker when repairing dc coupled audio amplifiers ..... this acted as a dc blocker and saved your speaker coils from burning up under amplifier output fault conditions.

    hope this helps,
    Rotarymaker
     

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