Pioneer SX-1080 Tuning meter stuck? Need help

Discussion in 'Pioneer Audio' started by rocknroller, Jun 26, 2017.

  1. kramden

    kramden Active Member

    Messages:
    138
    The first Pio meter that I was dealing with, acted very similar to how they do when the ground in the main variable capacitor go bad from oxidation with the exception of sometimes it would not deflect back to normal. Very sporadic. Sorry for such small writing in the reply pics; if you download the pics and view with an image utility like Irfan View, you can see them much better. The diameter of the wire I used was extremely small so that it wouldn't get hit by the armature housing as the needle deflected.
     

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    Last edited: Jul 10, 2017
  2. rcs16

    rcs16 Super Member

    Messages:
    2,965
    Location:
    Baldwin, Ontario, Canada
    If the meter uses the same IF quad IC, PAxxxx, then I am sure it will work.
    I said stop gap because having the correct one makes the unit original, not that it will not function as intended.
     
  3. rocknroller

    rocknroller Active Member

    Messages:
    190
    I'm not even certain it's the meter now. I found a replacement luckily at a decent price. came and hooked it up externally with some jumpers and worked fine. So I thought i was doen , installed it and buttoned the case back up... It did it again. Put an ohmmeter on it, deflected in both directions. Then power on - working fine. Powered on off several dozen times until it finally happened again. Checked for lose wires/connections. No change. Voltage present at the meter too, just as before.

    So I go back to look at my old meter and try a AA battery quick test - full rapid deflection - with only 1.5 volts, yes I see 4.5-6+ when in circuit with nowhere near that kind of deflection. So then it dawns on me - it must not have anything to do with the voltage but possible the CURRENT. So I set my meter for current mode and run some jumpers from one end of the tuning meter to my volt (amp) meter) and back on the new one. Of course the new one is working now so I'm seeing deflection and up to 75ua or so (close to zero when tuned and centered). Tried a dozen times to make the failure occur and FINALLY caught it happening. No meter movement, 0ua on my meter. I could only catch this condition once, but it made me think perhaps rather than a faulty connection in the meter (old or new) there is a circuit condition that somehow passes voltage through the meter, but not current? Schematic is hard to read but attached here. If the meter really had a bad internal connection, it shouldn't react to the ohmmeter test, right? And I've done that dozens and dozens of times. And while possible both old and new meters have the same physical issue, the inconsistency of it failing ONLY upon startup of the unit, rare and random, is quite odd. I've never seen either meter stop during use once it started. Only not work on power on.
     

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  4. kramden

    kramden Active Member

    Messages:
    138
    No current means an open in the loop. Bypass the correct contacts of S10 temporarily while the meter is it's "off state" (Run a jumper from the positive of the meter to pin 27 of the tuner board and a jumper from the negative of the meter to pin 28 of the tuner board) If it starts working while your jumper is across the contacts and stops working as soon as you take it off then there is your answer. (still betting it's inside the meter though if the switch has already been cleaned)
     
    Last edited: Jul 18, 2017
  5. rocknroller

    rocknroller Active Member

    Messages:
    190
    BINGO! Looks like the FM switch is the culprit. Took about 50 power ons to make it happen, then the jumper solved it. Then tried messing with the switch button to make it happen directly which it does. I assume the power on is really just shaking the unit enough to make that contact sporadic and random.
    I haven't pulled the board down, but these appear to be rectangular sealed type switches. Is there is access hole to spray in once I get the board down, or does it have to be disassembled?
     
  6. kramden

    kramden Active Member

    Messages:
    138
    Good head shots of the switch would help. But remember also that the switch is only one component in the path. Bad solder,busted copper,too much beer....you know the drill.
     
    Ricktptman likes this.
  7. rocknroller

    rocknroller Active Member

    Messages:
    190
    Yep - Got some in the front and worked it out. I think this puppy's done! Thanks to all for the forum support!
     
    Ricktptman likes this.
  8. kramden

    kramden Active Member

    Messages:
    138

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