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SX-650 Very Low Output on One Channel - All sources except tuner

Discussion in 'Pioneer Audio' started by spark1, Oct 23, 2018.

  1. Bill Ferris

    Bill Ferris Super Member

    Messages:
    1,687
    Location:
    NE. FL.
    Or-- your tuning into a highly compressed FM radio station, thus making any other signal source appear weak !!

    Hey !! With the heavy handed compression used on OTA transmissions, a OTA FM signal as a over all sensitivity reference against other inputs would be questionable IMHO/E !!
    A specially after cleaning/spraying out the function switch, and checking out the other line level inputs with a known reference source, whether a CD player, audio signal generator`s output set to the equipment`s input sensitivity specifications with a scope, and or ACVM connected to the speaker outputs, or tape outputs to get some idea if there is really a circuit issue.

    Just a thought..

    Good luck.
    Much kind regards, OKB
     

     

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  2. spark1

    spark1 Super Member

    Messages:
    1,480
    Location:
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    As I noted above, output is fine on both channels when using the tuner. Output is dramatically reduced on right channel with other inputs.
     
    Last edited: Oct 27, 2018
  3. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,806
    Location:
    Fort Dodge, Iowa
    Think again. This time review the schematic.:thumbsup:
     
  4. avionic

    avionic " Black Knights " Subscriber

    Messages:
    43,806
    Location:
    Fort Dodge, Iowa
    Check solder pin connections for switch Sa1.
     
  5. spark1

    spark1 Super Member

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    1,480
    Location:
    The Great Midwest
    Thx again avionic. I'll be digging into it later this evening.
     
  6. spark1

    spark1 Super Member

    Messages:
    1,480
    Location:
    The Great Midwest
    Success! I took off the front chassis plate again and used a stiff hobby paintbrush and deoxit to clean the selector switch contact points yet again. I then desoldered and resoldered all of the switch connections. Put things back together and sounds great; of course, since I didn't power it up until I had done the deep clean AND the resoldering, we'll never know which it was!

    I had already addressed a problem in the phono section, and this evening I went ahead and recapped it and the tone board (including the blue sanyo aluminum caps).

    Now all I have to do is prep, prime and paint the cabinet, and it will be good to go. The authentic woodgrain vinyl had some bad spots, so I peeled it off. I've done this on several of the lower end x50 and x80 receivers over the years, spraying them semi-gloss black and finishing with clear coat. I really like the way they look when done this way.

    Thanks very much to all who took the time to respond to this thread, especially avionic, whose direction clearly narrowed it down to the selector switch.
     
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  7. Watthour

    Watthour Electron Rancher - JS3600

    This whole endeavor will be useless without photos of the finished product (I'd be interested to see the results of the refinish).
     
  8. spark1

    spark1 Super Member

    Messages:
    1,480
    Location:
    The Great Midwest
    I may not get around to painting the cabinet for a little while...I have it and one from an SX-780 to do, and I've found that taking the time to set up a little spray booth in the garage provides much better results (keeps the dust off while the paint is setting up).

    In the meanwhile, here are a couple of pics of SX receivers I've done in the past:

    SX780g.jpg IMG_0080.JPG SX750.JPG
     
    Last edited: Oct 28, 2018
    Matthelm and avionic like this.
  9. Watthour

    Watthour Electron Rancher - JS3600

    Thanks. I like the look, contrasting the aluminum face with black. It's crisp.
     
  10. spark1

    spark1 Super Member

    Messages:
    1,480
    Location:
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    Me too. When I used this approach for the first time, I wasn't quite sure how it would turn out. But I too like the look...crisp is a good adjective. The black makes the faceplate really pop.
     
  11. Porkbuns

    Porkbuns New Member

    Messages:
    25
    I always am amused when its just bad contacts. Reassuring though.

    I once repaired an SX-737 that had only one channel out from the tuner and only the tuner. Turns out someone had desoldered a capacitor in the signal path and forgot to re solder it.
     

     

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  12. 0Hz

    0Hz AK Subscriber Subscriber

    Messages:
    268
    When I first read the description of what you were doing I thought "no, no no no no... noooooo" (I do love my real wood 636 cover) but I have to admit after looking at the pictures for a bit, it looks great.. almost good enough that I wouldn't mind owning one of these later silver-faced, full of levers, instead of buttons, receivers if it looked like that. :beerchug:
     
  13. spark1

    spark1 Super Member

    Messages:
    1,480
    Location:
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    If it had been a wood veneer, I would have repaired it. Not much you can do with that vinyl/plastic stuff they used.

    I have veneered a 750, and it came out quite nicely. Good experience, but not cost effective...took quite a bit of time.

    Did you take the vinyl off of your 636 and do the wood veneer yourself, or did you have it done?
     
    Last edited: Nov 5, 2018
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  14. spark1

    spark1 Super Member

    Messages:
    1,480
    Location:
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    Glad I could amuse you.

    If I had to bet, my money would be on a solder joint as the cause of the problem, given that the switch contacts showed no signs of serious oxidation, and given that they had been cleaned/"deoxit-ed" pretty well already.

    The switch assembly is board mounted, and years of use put a lot of stress on those joints.
     
    Last edited: Nov 5, 2018
    0Hz likes this.
  15. Porkbuns

    Porkbuns New Member

    Messages:
    25
    Ah! Well it's good that you got it running!
     

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