SX-1050 is not a virgin after all...

Discussion in 'Pioneer Audio' started by Stevescivic, Aug 25, 2017.

  1. Stevescivic

    Stevescivic Active Member

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    187
    Well my hopes of actually working on a unmolested unit came to a screeching halt tonight when I opened up the bottom of my unit. Looks like some moron took a cheap soldering iron and tried to solder the wire wrap connectors from the transformer to the power supply board. It also looks like they did some handy soldering work to the surge suppressor board too which might actually be supressor board from another model. Normally on the SX-1050 the suppressor has a single electrolytic cap. Mine doesn't have one yet the suppressor looks factory because it mI ntsvperfectly in the chassis. The tell tale sign that something isn't quite right is the missing capacitor and the fact that the soldering looks sloppy and some wires look like they were melted by a soldering iron due to carelessness. There is normally a wire wrap that also ties the thermal fuse to the huge round resistor and that appears to be missing and the thermal resistor isn't making physical contact with the giant resistor.

    Any suggestions on how to properly fix the wires? I was thinking of cutting back the melted portions and splicing some new wires and wire wrapping them to the pin posts.

    Drives me mental that I can rarely find anything that hasn't been messed with at some point in its life...
     

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  2. SaturationPt

    SaturationPt AK Subscriber Subscriber

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    That is disappointing, especially if there's damage that is difficult to reverse (such as burned / lifted solder pads).

    I have run into the sorority girl syndrome also (where it becomes obvious that you're not the first one in there) ... but most of the time you can make it right.
     
    merlynski likes this.
  3. Stevescivic

    Stevescivic Active Member

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    187
    Hahaha, sorority girl syndrome :) That being said, what is my best recourse to make this unit to be as near perfect as possible without breaking the bank?
     
  4. zebulon1

    zebulon1 This summer heat slowed me down. Subscriber

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    Once the posts have been soldered you can't go back and rewrap. The post has been compromised.
     
  5. KingBubba

    KingBubba "Too Much Stuff" Subscriber

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    Actually, the post should be considered compromised when it was unwrapped The act of wrapping wears on the post to the point that the edges are no longer sharp. As Zebulon said "You can't go back".
     
  6. petehall347

    petehall347 the brandy coffee man

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    new posts will fix it
     
  7. Stevescivic

    Stevescivic Active Member

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    So what can/should be done with it? Leave it as is since it is working still? Does anyone have some posts with the factory wire wrap still attached that they'd like to share with me so I can resplice the damaged posts?
     
  8. petehall347

    petehall347 the brandy coffee man

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    new posts wire and then you need the wire wrap tool .
    or if its working and it doesn't bother you leave it be .
     
  9. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Location:
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    I am assuming that "surge suppressor" in this case means the soft start circuit board (AWX-098).? Would you please post pictures of both sides of what is there to show how it differs from original?
    Thanks much!
    merlyn
     
  10. Stevescivic

    Stevescivic Active Member

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    187
    Well here are hopefully better pics of the surge board.
     

    Attached Files:

  11. merlynski

    merlynski Curmudgeon Electronicist Subscriber

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    Thank you!
    That board looks different than the one I have that matches the schematic I have.
     

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  12. QSilver

    QSilver Super Member

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    1,079
    Looks like you might be missing the ceramic ends of that resistor... is the thermal fuse there just under the resistor?
     
  13. Stevescivic

    Stevescivic Active Member

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    187
    There is a thermal fuse under the resistor but no capacitor.
     
  14. Stevescivic

    Stevescivic Active Member

    Messages:
    187
    I just looked at the supressor again and it definitely isn't AWX-098 but AWX-108 which from what I gather was a later generation of Sx-1050.

    So now I am legitimately concerned as some caps I yanked from the unit had slight deviations. For example. On the boards I yanked some caps rated for 50 volts yet the SM states 35 volts.

    I think we may neeed some experienced folks to chime in on what transistors or caps I need to sub out to make it work with later versions of the SX-1050.
     
    Last edited: Aug 29, 2017
  15. QSilver

    QSilver Super Member

    Messages:
    1,079
    If they've got a higher voltage rating, thats completely fine and probably a good idea. See if you can locate a schematic of your board AWX-108. Maybe your's is a later version? What's the serial number?
     
  16. Stevescivic

    Stevescivic Active Member

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    Well the thing is that the schematics call for a 47uF 35 volt cap but what I removed was actually a 47uF 50 volt cap.

    Does anyone have a schematic of the AWX-108? There aren't really any replaceable parts on it because it was working BEFORE I started the rebuild and the thermal fuse is working because otherwise the unit wouldn't power on.

    If you look at some previous pics in this thread you can see someone at one point in time was mucking around with the surge suppressor and the power supply b/c the wire twists were mangled and soldered back. The wires were haphazardly soldered and it looked like whoever was working on it had no regard to melting the insulation on the wires. Nothing is exposed per se but it sure makes for an ugly fix.

    I guess the argument is if it ain't broke don't screw with it. I had this receiver playing music for at least 3 hours over a course of a week or two before I tore into it rebuilding each board at a time. Tell tale sign that it was in dire need of a rebuild was one of the channels started cutting out and crackling. I immediately powered down the unit and started the rebuild. Although 99% of the caps pulled had the properly capacitance values 2 on the lower power supply board had drifted beyond 30% tolerance. I didn't measure the ESR on any of them but I suspect that caps develop high ESR before capacitance starts to decline.

    The unit sounded VERY good before it started failing on me so it will be interesting to hear how it sounds after all my handiwork.
     
  17. r887661

    r887661 AK Subscriber Subscriber

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    Sorry to hi-jack your posting but I'm getting no responses to my posting concerning the same surge protector and thermal fuse on an SX-5580. Mine smokes like heck on power up and I need some help and guidance. Please look for my post SX-5580 SX-1050 Smoking Hot.

    Once again, apologies.
     
  18. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Steve; PIONEER DID on occasion substitute higher voltage caps when the line ran out of a cap. This is a very common thing with the manufacturers. Actually with the 50V caps in there you have more voltage headroom as the circuit is probably running within a volt or 2 of the original cap voltage (not good). With today's higher wall voltages expect your internal voltages to rise about 4-5volts. If you are recapping the whole thing, look at the voltages around the caps. If it's less than 5 volt difference between the line voltage and the cap voltage, take the cap up to the next higher voltage. This will give the caps a bit of breathing space so they aren't running at close to max voltage.
     

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