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Can I fix this receiver?

Discussion in 'Electronic Repair' started by [email protected], Jan 9, 2004.

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  1. Guest

    My friend gave me a Technics SA-GX700 receiver. I wanted it to drive
    some fairly cheap outdoor speakers on the deck.

    She assured me it worked the last time they used it, but when I set it
    up, I get no sound, wither through speakers or headphones.

    I can see the graphic EQ responding to the tuner and the CD input.

    When I turn the unit on, I get a click (relay?), then about 2 seconds
    later another click.

    There is a cooling fan on the back that is not running. I'm not sure
    if this fan is supposed to run all the time, or just when needed.

    I took off the cover, and checked the three fuses I could find.
    They're good.

    I also disconnected the fan and checked the voltage of the pins that
    supply power to the fan: .2 V.
     
  2. Guest

    I noticed that the second "click" is coming from a component marked
    "Type DH2SU 24VDC."

    Is this a protection relay?
    If so, where do I look upstream for what's tripping it?

    I don't have any speakers connected...just headphones.
    If I turn the volume to maximum, I can hear a tiny signal in the left
    headphone; nothing in the right.
     
  3. Sofie

    Sofie Guest

    Mitch:
    Before you tear anything apart you might want to confirm that you have not
    inadvertently left a tape monitor switch on.....
    or if you only have one set of speakers hooked up make certain that you only
    have that one set turned on with the buttons on the front...... if both
    sets of speaker ( A & B ) jacks are turned on with only one set hooked up
    you will not get any sound.....
    and check on the back panel, if there are jacks on the back for PREAMP OUT
    and MAIN IN, then you must jumper the outputs to the inputs or there might
    be a switch near the jacks that will accomplish that task.
    If non of these suggestions help..... try plugging in some headphones.....
    sound?
     
  4. Sofie

    Sofie Guest

    Mitch:
    Yes... this is a protection relay and it is suppose to click to turn on the
    speakers a few seconds after power on. I would guess that either a tape
    monitor switch has been left on or jumpers are missing on the back if this
    receiver has jacks for preamp out and main amp in.
     
  5. Guest


    It's definitely not Tape Monitor, as I switched this off and on
    several times.

    But there ARE Pre Out / Main In jacks on the back...with no jumpers!

    Can I jumper these with plain RCA cables?

    I'm waiting eagerly for your reply!
     
  6. ampdoc

    ampdoc Guest

    Yes, RCA cables are fine.

    --
    Jammy Harbin
    J & J Electronics, Inc
    227 S. 4Th St.
    Selmer, TN 38375
    731-645-3311
     
  7. Sofie

    Sofie Guest

    YES.... jumper with cables.
     
  8. Guest

    FIXED!

    Well, wasn't broken. :)
    In any case, THANK YOU a thousand times.
     
  9. jakdedert

    jakdedert Guest

    Good deal, Mitch. BTW...the jumpers usually supplied with receivers like
    this are simply a piece of bare wire bent into a 'U' shape which connects
    'only' the center pins of the RCA connectors. If--like me--you dislike
    'cable clutter' or you need your cables for connecting components; you can
    fashion jumpers from a couple of chunks of ten gauge wire. Make sure you
    get the bend and spacing accurate, or you will short the signal to ground
    (or damage the jacks)...no damage possible, but one or both channels will
    not work. It should push straight in with a bit of resistance, but not
    short against the outside of the jack.

    jak
     
  10. Guest

    Thanks, I may try that.

    One more question. The cooling fan isn't on.
    Should it run constantly, or does it turn on and off as needed?
     
  11. Sofie

    Sofie Guest

    Mitch:
    The speed of the fan is temperature modulated ..... when you use the amp at
    high power levels, it will come on, just make certain that you reconnected
    the connector that you removed when you measured the voltage.
     
  12. The speed of the fan is temperature modulated ..... when you use the amp at
    Actually, with a lot of Technics receivers, the fan comes on in response to the
    load levels of the output section. If you turn the volume up with nothing
    playing through the set input, the fan won't run. But, if you play something
    loud on that same input and run it at moderate volume, the fan may come on in
    response to the increased demand to the ampilifer ICs. (Don't know of many
    Technics receivers that actually used transistors in place of ICs for the
    output sections.)

    This execution of the cooling fan was a real serious problem with the Technics
    SA-DX930. That receiver almost always had a tendency to overheat. - Reinhart
     
  13. Guest

    Oh, no.

    The receiver was working great.
    But since the main music source is my PC (CD's, MP3 collection, etc),
    I wanted to use the receiver and speakers to monitor my PC audio
    signal.

    No problem.

    However, I also wanted to be able to direct that audio signal to my PC
    speakers OR the receiver. So I ran the PC audio signal to a system
    selector, and ran one output to the PC speakers, and one output to the
    receiver.

    Again, no problem. It's been working great.

    Today, however, I went to switch the selector to the receiver, and the
    receiver quit on me.

    I realize now that I shouldn't have been switching it back and forth
    while the receiver was turned on!

    Thw standby light is on, but when I turn the unit on (and I still get
    the two relay clicks, about 2 seconds apart), the display only says
    "CD," and all of the other info is blank. If I switch to tuner, it
    just has the freq. number, and no other info.

    More importantly, the red LED on the volume knob is not on.

    I checked (with a multimeter) the three fuses I can see (are there
    more?), and they are all good.

    Did I ruin the receiver?

    Stupid, stupid, stupid! It was working great until I had to put that
    dang switchbox in!
     
  14. Brand and model number of the receiver might help.

    mz
     
  15. Guest


    Technics SA-GX700
     
  16. If you're lucky, maybe just a blown fuse or other fusible device. Obviously
    a part of the power supply is dead, but there is a distinct chance, given
    your description, that an output IC is blown with a resulting blown fuse(or
    2). Technics models generally use proprietary, expensive output devices.

    Mark Z.
     
  17. Guest

    There are three fuses visible near the power supply.
    Would there be additional fuses under the boards?

    Would shorting the CD inputs have caused this?
     
  18. Sofie

    Sofie Guest

    Mitch:
    No, no other fuses are under the boards.
    No, shorting any of the inputs will NOT cause failures.....
    .....but, shorting the speaker wires or hooking up too
    many speakers can cause immediate failures, most of
    the time more serious and more expensive to repair
    than just a blown fuse.
     
  19. Guest

    I'm pretty sure there was no speaker shorts.
    The unit was working, then suddenly it wasn't.
     
  20. Sofie

    Sofie Guest

    welcome to the world ..... things break..... even new things.
    ------------------------


    ..
    ..
    ..
     
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