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SA 7500 MKII Volume problems and Protection Relay

Discussion in 'Pioneer Audio' started by robertv, May 17, 2018.

  1. robertv

    robertv AK Subscriber Subscriber

    Messages:
    13
    Location:
    Griffin, GA
    I picked up a SA 7500 MkII at an estate sale last week, and I ran into some problems which, after I did some researching on here, appeared to be very typical with this unit. After thorough Deoxiting, I continued to have a scratchy volume control with one channel that repeatedly went out. But if I turned up the volume loud, the channel would "push through" and come back. Following the information in this thread,

    http://audiokarma.org/forums/index....-7500-ii-protection-relay-replacement.696990/

    I purchased a new protection relay and installed it. And the problem got better. No scratchiness, and everything seems fine for long playing periods. Then, suddenly, the same channel goes quiet. Not out, but very quiet. And now the volume "push-through" trick no longer fixes it. BUT, if I simply turn the unit off and then back on, it's fixed, at least for a good while... then gone again. Off-On, fixed. So it's gone from non-operational to annoying.

    My skills are very limited; I'm fairly proficient with soldering, so when there's a thorough explanation on here like the one in the thread above, I can handle the repair. But as far as real trouble-shooting on my own, I'm lost in the woods.

    Anything else that I can try, or do I just need to turn this thing over to an expert?
     

     

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  2. loweran

    loweran AK Subscriber Subscriber

    Messages:
    1,009
    Location:
    Austin, Texas
    Man, I went through the same thing. The issue is the volume control is very sealed. It's hard to get the deoxit in there. I would drop a channel at low volumes on startup, turn it up and it fixed itself. I ended up replacing the relay and that seemed to cure it. I sold it and cant say for sure that it is completely cured. Very much the same symptoms you report. Try hitting the volume pot again with deoxit. Otherwise, you may need to retro fit a different volume pot in there. I read that you can put one in minus the board that the original is on.
     
  3. playittwice

    playittwice Well-Known Member

    Messages:
    637
    Location:
    Dubuque Iowa
    Did you get this resolved?
     

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