Connect with us

Pioneer sx-727 radio dead

Discussion in 'Electronic Repair' started by [email protected], Apr 26, 2008.

Scroll to continue with content
  1. Guest

    I have a pioneer sx-727 receiver, I'm the original owner (33 years).
    Recently the radio stopped working.
    Everything else works great.
    FM, AM no difference does NOT work.
    The tuning meter does not move as I turn the tuning dial.
    If I turn the volume up, I can hear some static thru the speakers.
    Occasionally the radio will spontaneously work for a while,
    and then return to this dead mode.
    All the other inputs cd, turntable work fine.
    Any ideas what the problem might be?
    Thanks.
     
  2. Bob Shuman

    Bob Shuman Guest

    Sounds like something is intermittent in the radio section (assumes
    amplifier/auxiliary input/tape/etc. all are still working fine). I'd start
    by looking for cold/broken solder connections under a magnifying. Or
    alternatively, if that does not work and you can get at the board safely
    while the unit is powered up, you can try pushing at various points with a
    wooden dowel or similar non-conductive item. This may help you isolate the
    area to take a closer look.

    If these do not help, then you'll either need a schematic, a volt meter,
    scope, and some troubleshooting skills to check the power supply voltages at
    key points and then follow the signal through the radio section or take it
    to someone to do the work for you.

    Bob
     
  3. Guest

    OK I took the thing apart and sure enough, there was a sanyo 313E
    mounted on a V shaped piece of metal(heatsink?). When I tapped
    gently on the metal, everything now works fine.
    The small board in question is AWR-011A, which according
    to the schematic is the power supply unit.
    I would think that if this was the roblem it would effect
    everything, not just the radio.
    Anyway I will run it for awhile with the case open,
    and see if the problem recurs.
     
  4. OK I took the thing apart and sure enough, there was a sanyo 313E
    mounted on a V shaped piece of metal(heatsink?). When I tapped
    gently on the metal, everything now works fine.
    The small board in question is AWR-011A, which according
    to the schematic is the power supply unit.
    I would think that if this was the roblem it would effect
    everything, not just the radio.
    Anyway I will run it for awhile with the case open,
    and see if the problem recurs.



    Resolder the 313 regulator.

    Mark Z.
     
  5. Mr. Land

    Mr. Land Guest

    I worked on a bunch of these in a previous life.

    It has been a long time, but I seem to remember a common problem of a
    voltage regulator in the power supply section becoming thermally/
    mechanically/whateverly intermittent. If the entire tuner section is
    going dead, this might be worth looking for. Seems a reasonable
    candidate if the tuner works occasionally as you stated.

    Look for a 3-pin voltage regulator in a TO-220 case - might not even
    be on a heatsink. Try tapping it with something non-conductive, or
    heating it, or freezing it, or, you might actually measure its output
    voltage. Worth a quick look, I suppose.
     
  6. Mr. Land

    Mr. Land Guest

    Whoops, sorry, I missed the last reply or two. I guess mine was
    redundant/unnecessary.
     
  7. Chuck

    Chuck Guest


    The 2SD313 transistor itself was know for going intermittent. Replace
    the transistor. A NTE198 or 2SD613 works fine. Chuck
     
  8. Guest

    I have left the case open, and have the thing sitting on a shelf
    vertically.
    It worked flawlessly for about 3 days, then spontaneouslt the radio
    went dead again.
    I ever so gently tapped the heatsink that this transistor is on, and
    once
    again everything is fine. I have not lifted the board yet to look at
    the solder
    underneath. However I'm beginning to think that it is the transistor
    itself
    that is the problem. Can I find the exact replacement at radio shack?
    If I'm going to lift the board, I'm thinking it's probably makes sense
    to replace the
    device.

    Thanks
     
  9. I have left the case open, and have the thing sitting on a shelf
    vertically.
    It worked flawlessly for about 3 days, then spontaneouslt the radio
    went dead again.
    I ever so gently tapped the heatsink that this transistor is on, and
    once
    again everything is fine. I have not lifted the board yet to look at
    the solder
    underneath. However I'm beginning to think that it is the transistor
    itself
    that is the problem. Can I find the exact replacement at radio shack?
    If I'm going to lift the board, I'm thinking it's probably makes sense
    to replace the
    device.

    Thanks


    Just resolder the transistor. You will see that the solder connections there
    have ring cracks from age and heating / cooling over the course of time.
    Common problem.

    Mark Z.
     
  10. Guest

    Hi ,

    I decided to lift the board and look at the solder for the device
    sanyo 313e.
    Before I could do anything the V shaped metal (heatsink?) attached to
    the
    device just fell off. The plastic screw holding it had just cracked in
    half.
    There also is a thin piece of plastic between the device and the
    heatsink.
    I'm assuming that they do want the device to touch the metal.
    I could not find a another plastic screw, so I use a metal one with
    an
    insulating washer. I hope that is ok. Why does the device need to be
    insulated from the metal heatsink. Is it strictly pecautionary, in
    case
    the heatsink comes in contact with something else. Would it be ok
    to put some cpu grease between the device and the plastic insulator?
    Anyway after all this the solder looked ok, so I did not resolder.
    I wonder if my problem all along was that the heatsink
    was just hanging on by a thread.
    Anyway it seems to work ok. I'll run it for a while with the case
    open
    as a precaution.

    Thanks
     
  11. Guest

    Hi ,

    I decided to lift the board and look at the solder for the device
    sanyo 313e.
    Before I could do anything the V shaped metal (heatsink?) attached to
    the
    device just fell off. The plastic screw holding it had just cracked
    in
    half.
    There also is a thin piece of plastic between the device and the
    heatsink.
    I'm assuming that they do want the device to touch the metal.
    I could not find a another plastic screw, so I use a metal one with
    an
    insulating washer. I hope that is ok. Why does the device need to be
    insulated from the metal heatsink. Is it strictly pecautionary, in
    case
    the heatsink comes in contact with something else. Would it be ok
    to put some cpu grease between the device and the plastic insulator?
    Anyway after all this the solder looked ok, so I did not
    resolder.
    I wonder if my problem all along was that the heatsink
    was just hanging on by a thread.
    Anyway it seems to work ok. I'll run it for a while with the case
    open
    as a precaution.


    Thanks
     
  12. Jamie

    Jamie Guest

    The metal back plane of the component most likely has connection to one
    of the electrical pins which can not be shorted to the case.
    this is common.


    http://webpages.charter.net/jamie_5"
     
  13. as a precaution.
    If the solder is really OK, which I doubt. Then the transistor is failing.
    On this TO-220 case transistor this most commonly happens from a
    base-emitter junction opening up internally.

    If you were to look very closely at the solder connections ( I recommend a
    magnifying glass) I believe you will see the ring-cracks around the
    transistor leads.

    In this particular case the heat sink has no other electrical connection,
    but you are still going to need another screw and nut. Another mica
    insulator and some silicon grease would be good, although as I say, in this
    case I think you could dispense with the mica.

    Alternatively you could use a newer style TO-220PL plastic case transistor
    such as a 2SC4793 which requires no insulator.

    It's unfortunate in a way that your skills and experience don't seem to
    quite be up to the task. I don't say that as a put-down, but this whole
    thing should have been over long ago.

    If you decide to replace the transistor, you'll need a source for the part,
    and most suppliers have 15.00 to 20.00 minimum orders.

    You might consider OEQuotefix to fix your problem with Outlook Express
    making messy looking posts. It's a free download.


    Mark Z.
     
  14. Guest

    No need to be nasty.
    The solder looked ok to me.
    The board is very old, so the plan is to proceed cautiously.
    I have attached the device properly to the heatsink.
    If the problem recurrs, I will reheat the solder joints.
    If that does not solve the problem then I will replace the device.
    I'm assuming that a 2sd613 will be an adequate replacement, correct?
     
  15. No need to be nasty.
    The solder looked ok to me.
    The board is very old, so the plan is to proceed cautiously.
    I have attached the device properly to the heatsink.
    If the problem recurrs, I will reheat the solder joints.
    If that does not solve the problem then I will replace the device.
    I'm assuming that a 2sd613 will be an adequate replacement, correct?

    *****************************
    A 2SD 613 would be fine.

    I'm not sure why the > marks aren't showing in the quoted sections, I had to
    add them manually last time.

    I don't feel I was being nasty before, even said so:

    I was watching as several other responders were telling you to replace the
    transistor and a lot of back-and-forth when as I say this coulda / shoulda
    been over with long ago.

    mz
     
  16. Guest

    OK thanks sounds good.
    One more question.
    In the process of lifting the board to examine underneath,
    the plastic tabs that hold the board in place are very brittle.
    One broke and the others half broke off. Can I pull these out
    from the side that the power supply board is on?
    I'm thinking that mayb I can replace these with some
    computer mainboard ones that I have lying around?

    Thanks
     
  17. Yes, if the area to be soldered can only be accessed by pulling the board
    up - it's been a long time since I've worked on a 727. I was thinking the
    board could be accessed from underneath.


    Mark Z.
     
  18. dBc

    dBc Guest

    Greetings TX7123 & others..

    Regarding:
    "If you decide to replace the transistor, you'll need a source for the
    part, and most suppliers have 15.00 to 20.00 minimum orders."

    Consider:
    http://www.electronix.com/catalog/product_info.php/products_id/3545
    http://www.mcmelectronics.com/content/ProductData/Catalog50/section16.pdf
    http://www.rcetronics.com/transist.htm
    ( "No order is too small." )

    For the datasheet on a 2SD613:
    http://www.littlediode.com/components/product.php?productid=46727&cat=287&page=209
    ( click on, Click Here, at the page - make sure you have Adobe
    Reader )

    Incidentally, Mouser does not have a minimum order however, they do
    not show stock on a 2SD613. Needless to say shipping has gone way up
    for *everyone.*
    http://www.mouser.com/

    At 1490 pages, Mouser [typically] has what you need. I don't doubt
    that they have an equivalent to the 2SD613 in stock. However, with
    the above actual transistors, you have alternatives.

    Regarding the 2SC4793:
    http://www.mouser.com/Search/Refine...&OriginalKeyword=2SC4793&Ntk=Mouser_Wildcards

    Cheers,
    Mr. Mentor




    |
    |
    | On May 3, 5:19 pm, "Mark D. Zacharias" <>
    | wrote:
    | >Hi ,
    |
    | <SNIP>
    |
    | > I decided to lift the board and look at the solder for the device
    | >sanyo 313e.
    | >Before I could do anything the V shaped metal (heatsink?) attached
    | >the
    | >device just fell off. The plastic screw holding it had just cracked
    | >half.
    | >There also is a thin piece of plastic between the device and the
    | >heatsink.
    | >I'm assuming that they do want the device to touch the metal.
    | >I could not find a another plastic screw, so I use a metal one
    with
    | <an
    | >insulating washer. I hope that is ok. Why does the device need to
    | >insulated from the metal heatsink. Is it strictly pecautionary, in
    | >case
    | >the heatsink comes in contact with something else. Would it be ok
    | >to put some cpu grease between the device and the plastic
    | > Anyway after all this the solder looked ok, so I did not
    resolder.
    | >I wonder if my problem all along was that the heatsink
    | >was just hanging on by a thread.
    | > Anyway it seems to work ok. I'll run it for a while with the case
    | >open
    | as a precaution.
    |
    | >Thanks
    |
    | If the solder is really OK, which I doubt. Then the transistor is
    failing.
    | On this TO-220 case transistor this most commonly happens from a
    | base-emitter junction opening up internally.
    |
    | If you were to look very closely at the solder connections ( I
    recommend a
    | magnifying glass) I believe you will see the ring-cracks around the
    | transistor leads.
    |
    | In this particular case the heat sink has no other electrical
    connection,
    | but you are still going to need another screw and nut. Another mica
    | insulator and some silicon grease would be good, although as I say,
    in this
    | case I think you could dispense with the mica.
    |
    | Alternatively you could use a newer style TO-220PL plastic case
    transistor
    | such as a 2SC4793 which requires no insulator.
    |
    | It's unfortunate in a way that your skills and experience don't seem
    to
    | quite be up to the task. I don't say that as a put-down, but this
    whole
    | thing should have been over long ago.
    |
    | If you decide to replace the transistor, you'll need a source for
    the part,
    | and most suppliers have 15.00 to 20.00 minimum orders.
    |
    | You might consider OEQuotefix to fix your problem with Outlook
    Express
    | making messy looking posts. It's a free download.
    |
    |
    | Mark Z.
    |
    |
     
  19. Guest

    Well just when I thought everything was fixed...
    The receiver had worked flawlessly for over 3 weeks.
    Then suddenly today the radio went dead again.
    I took it apart and this time reheated one of the solder
    joints on the questionable transistor (d313e).
    Anyway everything is back together and working.
    Hopefully this will permanently fix the problem.
    The plastic tabs that hold the board in place are disintegrating.
    Anybody know where I can get similar tabs?
    Thnaks.
     
  20. Jamie

    Jamie Guest

    You mean nylon stand offs?
    places like Mouser, Digikey etc.. have hard things like that.


    --
    "I'd rather have a bottle in front of me than a frontal lobotomy"

    "Daily Thought:

    SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
    THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
    http://webpages.charter.net/jamie_5"
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-