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Pioneer SA-9500 turns off/on at random.

Discussion in 'Pioneer Audio' started by St. Pierre, Dec 12, 2016.

  1. St. Pierre

    St. Pierre Active Member

    Messages:
    380
    Location:
    Michigan
    I have read all the forums that touch on this about other amplifiers and receivers. The problems all turned out to be external issues, (speaker impedance, bad connections, ect.) I have thoroughly check repeatedly for any of these to be the source of this problem. This unit is extremely clean, new connection cables, new 14 gauge speaker wire, speaker impedance of 7.1ohm. This problem only happens when the volume is more than 2 (second click of volume control) 3 to 6 clicks it happens within 5-10 minutes, 10+ clicks happens immediately. Also when the unit is shut off there is a loud pop through the speakers, even when the volume is turned down. How can these issues be corrected? Thank you AK!
     
  2. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

    Messages:
    20,537
    Location:
    Bensenville,Illinois
    Interesting, the symptoms conflict.

    Is there the usual 3 to seven second protection delay when the unit is turned on? Before sound comes through when the protection relay clicks in.

    First check the power supply voltages, rebuild the power supply if not spot on.
    Second rebuild the protection, no checks needed - the volume problem is the old (solid aluminum, sky blue sanyo's) caps on the over current detector. The "discharge transistor" is probably toast if the turn off pop isn't suppressed (unless the relay contacts have welded themselves) BUT the "turn-off" related to the volume control setting wouldn't be happening.
    Third check the offset voltages at the power amplifier output. There are three or more EXTREMELY problematic transistors in each power amp channel. They should be preemptively replaced.
     
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  3. St. Pierre

    St. Pierre Active Member

    Messages:
    380
    Location:
    Michigan
    Yes there is approximately a 5 second protection delay when turned on (no pop) every time. About 50% of the time there is a pop when turned off, I've noticed this to occur more often after the random off/on happens. I've called just about every vintage audio repair man here in Michigan Google can provide. Their clueless and have suggested that I get another Amp. Absolutely not is my response. I love this Amp, and these issues only recently started to occur. I'm actually listening to Buddy Guy at this very moment. Volume is at 2 clicks, no distortion, crystal clear. I know this is a problem that can be resolved once I find the source.
     
  4. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

    Messages:
    20,537
    Location:
    Bensenville,Illinois
    Power supply rebuild will also cure timing problems that happen because of capacitance loss - something is dropping faster than the relay is disconnecting the speakers during power loss / power down. Protection drops pretty quickly, so something is barely hanging on.

    The SA-9500 is a mechanical challenge to do a rebuild on. Not something to cut your teeth on. Photographs and COPIOUS notes - the notes should be of a format where they are notes from you, TO you, instructing yourself how that &*^&*^*&^ thing goes back together - for when you ask yourself in exasperation "HOW does that &*^&*^*&^ thing go back together???"

    The upshot on doing all this at once is that then you shouldn't have to do it again for a long long time (like 2 decades). We KNOW where the problems crop up, and you would be instructed on how to kill all of them. MOST are just dried out e-caps, some are failed sanyo e-caps, and some are transistors that have proved their lives are short and unpredictable.
     
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  5. CraigJ

    CraigJ New Member

    Messages:
    9
    I have the same issue on a recently acquired SA-9500. Works great with good clarity. The power light was burned out when I got it. Noticed last night that the unit was warm. There is no audible click when it is turned on. Checked again this morning and it was still warm. With the power pushbutton out/not depressed it played through my turntable. Pushing the button in/depressed had no effect. Other that this it is fine. I am somewhat leery of using it. Any suggestions?
     
  6. St. Pierre

    St. Pierre Active Member

    Messages:
    380
    Location:
    Michigan
    I took mine to a tech and had it fully rebuilt to factory specifications. It works perfect now, total cost of rebuild was $125.
     
  7. CraigJ

    CraigJ New Member

    Messages:
    9
    I thought about just plugging it up to a terminal strip and powering it down...
     
  8. LesE

    LesE 110284 Subscriber

    Messages:
    552
    Location:
    Ontario, Canada
    The power switch contacts can become stuck in the on position as the result of arcing. That's what happened to my SA-9900. I opened the switch and the fused contacts immediately separated. Sometime later, I performed the following mod to preserve the power switch.

    http://audiokarma.org/forums/index....orth-5-and-an-hour-or-so-of-your-time.504673/

    Les.
     

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