Need help with repair of a pioneer receiver

Discussion in 'General Electronics Chat' started by lubnaan90, Jul 27, 2013.

  1. lubnaan90

    Thread Starter Active Member

    Jan 13, 2010
    196
    2
    Hello members,

    Have this problem with my pioneer receiver SC-LX82 would not start, when powered up the display lights up for about 2-3 secs then shoutsdown & Phase control LED keeps flashing.

    Tried the resetting method but no luck, completely diassembeled the receiver, Checked all the transistors inside the amplifier section, checked for short circuits but all seems to be OK, all OK even with the power supply.

    Any suggestions or help will be deeply appreciated.
    P.S. I do not have the service manual of this particular model, if anyone can help me get that then I would deeply appreciate that.

    Thanks in Advance.
     
  2. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
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    Last edited: Jul 27, 2013
  3. lubnaan90

    Thread Starter Active Member

    Jan 13, 2010
    196
    2
    Hello,
    Many Thanks for writing. Still no luck, i did find some flat cables loosely connected (wondering how that might have happened), connected the cables properly but still the same thing. seems like I need to try a complete reset or something.

    Thanks for the links, when there is nothing left to do i will buy the serivice manual.
     
  4. trader007

    Active Member

    Feb 27, 2010
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    lubnaan90 likes this.
  5. lubnaan90

    Thread Starter Active Member

    Jan 13, 2010
    196
    2
    Million Thanks to you, Tried my best to search the manual for free but no sucess, i wonder why it's not available for free of charge. Anyways thanks again for your understanding & help. WIll keep posted.
     
  6. trader007

    Active Member

    Feb 27, 2010
    222
    19
    It is available online for free. There is a guy who runs a website that provides a f-ton of service manuals for free, but limited 2 downloads per day.

    http://elektrotanya.com/

    If you pay I think you can get unlimited downloads.
     
  7. lubnaan90

    Thread Starter Active Member

    Jan 13, 2010
    196
    2
    Hello Members,
    Sorry for the long silence from my side, like many other members of this forum I get only the weekeneds to work on my projects/repairs.

    Now to the point...
    Based on the symptoms of the receiver (AC220v relay cuts off after 5 secs of startup, within these 5 secs the HDMI LED blinks & the receiver shuts down after that & the Phase control LED keeps blinking non stop). After following the instructions in the service manual i hope & Believe that i have found the problematic area on the Digital Main deck assy PS Block.

    Please take a look at the attachements to better understand what i am trying to describe.

    The manual says to check L1931 which should have around 3.3v, when tested, one side of L1931 has 3.3v while the other side shows -1.5v (Negative), then i check Q1930 which should have 16.5v on pin 5 & 6 but my reading shows around 13v. The same is with L1932 which should have around 1.8v, when tested, one side of L1932 has 1.8v while the other side shows -1.5v (Negative), then i check Q1930 which should have 16.5v on pin 7 & 8 but my reading shows around 13v.

    Before I proceed, I would be happy to know, What you guys think about this? I'll deeply appreciate any recommendations before I proceed.
     
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  8. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,762
    924
    Try something.

    I have repaired two pioneer sets. Both had strange power fluctuation symptoms. Occasionally they would work for a few seconds, then the light would dim or flicker and the units would stop working.

    Locate the power switch connections on the back of the switch and solder a shorting wire across them.

    Power on the unit by plugging it into the wall outlet.

    In my case the problem was cured by this 'bypass' of the power on switch. Seems the contacts had deteriorated and become resistive and intermittent.

    It is a simple check and is easily reversible if found to be ineffective.
     
    lubnaan90 likes this.
  9. lubnaan90

    Thread Starter Active Member

    Jan 13, 2010
    196
    2
    Thanks for your reply, the symptom you mentioned is exactly the same as appears here in the receiver i have "Would work for a few seconds, then the light would dim and the unit stops working"

    SOldering a shorting wire across the power switch connections is unsucessful, the receiver becomes totally unresponsive.

    What do you think about the problem i found & the Scheme I uploaded above?
     
  10. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,762
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    I am confused by your use of the word 'unresponsive'.

    Shorting the power/on-off switch and using the power cord to turn on the unit, gives you a DIFFERENT problem than the one you are currently troubleshooting?

    Bypassing the switch SHOULD give you the SAME problem, or fix the problem.

    The switch is just a metal contact, shorting around the switch cannot possibly cause a different problem unless you have made a mistake in your application of the shorting wire.

    double check your work on this.





    In your schematic I see a large electrolytic cap (C1930) is common to both points where you are getting the 13V reading.

    The IC (IC1930) also has a PGOOD signal on pin 15. Monitor that at startup and note how it behaves when the unit is momentarily working, and when the problem begins.
     
  11. lubnaan90

    Thread Starter Active Member

    Jan 13, 2010
    196
    2
    PLease allow me to clear something.
    By shorting the power on/off "SWITCH", do you mean the on/off switch located on the front panel of the receiver (Like the one I have attached below)

    About checking the PGOOD, how do you suggest to check that, should i check the voltage?
     
    Last edited: Aug 11, 2013
  12. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    I have made a mistake. I thought your power switch was mechanical in design. Having metal contacts which are brought together or separated by mechanical means.

    Your switch does not seem to be of this design. the switch you illustrated would function by sending a voltage 'command' to a controller which operates a relay, or a semi-conductor device which then supplies power to the unit. If the unit uses a relay, you should examine it closely for contact damage.

    The PGOOD signal should be a logic 'high' when active. monitor it with a volt meter.
     
  13. lubnaan90

    Thread Starter Active Member

    Jan 13, 2010
    196
    2
    I thought so. I had a feeling earlier that you were referring to those old type push lock on/off mechanical switch.

    Anyways I will check for PGOOD later on & update.
     
  14. lubnaan90

    Thread Starter Active Member

    Jan 13, 2010
    196
    2
    HELLO,
    I searched for the large electrolytic cap (C1930) which is common to both points where I am getting the 13V reading. For some reason the Capacitor is not availabe on the PCB. there is a place on the board where it should be soldered but it is absent.

    As for the PGOOD i am not getting more then 5vDC on pin 15 of IC1930
     
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  15. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    5volt is a good positive logic level for the PGOOD signal.

    Trace the AC power into the unit.

    find it where it enters the unit and probe each point along its course to see that it makes it to the power supply section transformer. I would hope you might find a relay in the power input pathway.
     
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