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Pioneer SX-880 Cutting out

Discussion in 'Pioneer Audio' started by coreseller, Sep 5, 2006.

  1. coreseller

    coreseller New Member

    Messages:
    24
    Howdy people, I'm a newby here but I've been a fan for awhile of the SX Pioneer silver face receivers. I have been picking them up here and there for a few years but it seems as if each one has it's own peculair problem (not holding FM stations, AM sections etc.) . Anyway, my real question is this; I have a very nice SX-880 right now in my garage that I just switched out an ailing SX-780 for. The 880 sounds great, all tuner sections work well, the problem is that it shuts off when turned up near or over the 8 to 9 o'clock position. It will come back on with an audible (from the receiver, not through the speakers) click when I turn the volume back down. I really don't want to take it in for work and I have done some simple repairs on these type of things in the past, any help would be appreciated, thanks.....Mark.
     

     

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  2. markallen

    markallen Luddite Tendencies

    Messages:
    1,144
    Location:
    Bismarck ND
    Common Problem SX-880/890 Series

    Not the classic symptoms, but I'm still going to guess the problem is a common one for which this model is known. I've had four SX-880/890 series and three came with this problem. I'll go out on a limb and say it wouldn't be very long and your SX-880 would not click on at all when you throw the power switch.

    The design is such that a particular transistor (there are three, actually, but a specific one is usually the culprit) in the power supply circuit gets VERY hot; over time, the solder joint cracks and you can have intermittent contact problems. Eventually, you'd turn the receiver on and the relay won't kick in. The dial lamps will light up, but that's it.

    You need to re-solder the problem transistor. To help you locate it, I've attached a picture of one of mine. It's the one near the middle lined up with two dark blue caps. As you can see I've also added a heat sink to the U-shaped channel that surrounds this particular transistor (it's hard to see, but it should be a SD712) to help prevent the problem in the future. Open the bottom of the case and you'll see the mainboard is darkened from the heat, and close inspection will likely reveal the broken solder joints. As long as you've got it open, resolder the other two nearest the SD712 as they get hot also.

    There are other references to this problem in AK. Check the thread titled "SX-880 overheating..". I don't know how to link to it, you can use the search function. Hope this helps!
     

    Attached Files:

  3. coreseller

    coreseller New Member

    Messages:
    24
    I really appreciate it Markallen. I ran a search before but not one specific to overheating.....mark.
     
  4. markallen

    markallen Luddite Tendencies

    Messages:
    1,144
    Location:
    Bismarck ND
    You are welcome, let me know if you have any other questions. I'd be interested to know if this solves the problem.

    Good luck!
     
  5. avguytx

    avguytx AK Subscriber Subscriber

    Messages:
    8,974
    Location:
    Central AR
    What are the difference between an SX-880 and the 890? I've been looking at one locally that is having "issues" and this may describe it. It's the SX-890 that I'm looking at.
     
  6. Fernzee

    Fernzee Heyyyyyy

    Messages:
    485
    Location:
    Twin Cities, Minnesota
    The 890 is the black-faced, european version. If you can get it, I say do it. The black-faced ones are rare in the US.

    Coreseller,
    You may also want to check the bias adjustment on your 880. If it is off-kilter, it will cause over heating. Check in the Vintage Solid State forum under the thread titled, DC Offset and You.
     

     

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  7. avguytx

    avguytx AK Subscriber Subscriber

    Messages:
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    Is it just black faced on for where the tuning dial, meters, etc is? The rest of it is silver.
     
  8. markallen

    markallen Luddite Tendencies

    Messages:
    1,144
    Location:
    Bismarck ND
    The only difference is that the SX-890 has the black dial with white lettering - and is FAR more RARE. I have one of each of the SX-590, 690, 790 and two 890s and would like to learn more about them. I've appealed for information on the SX-x90 series here on AK but so far nothing. Definitely collectors' items, in my estimation.

    I'm guessing you're considering the 890 that is selling in a few hours on eBay in the Dallas area; I have been watching that one and if I could pick it up in person I'd go for it. I don't want to pay $35 shipping, though. If you do get it and the repair I described above works, I'd be interested to know. Good luck!
     
  9. Fernzee

    Fernzee Heyyyyyy

    Messages:
    485
    Location:
    Twin Cities, Minnesota
  10. Fernzee

    Fernzee Heyyyyyy

    Messages:
    485
    Location:
    Twin Cities, Minnesota
  11. avguytx

    avguytx AK Subscriber Subscriber

    Messages:
    8,974
    Location:
    Central AR
    Yep...that's the one I'm looking at. It's about 45 minutes to an hour away from where I live, but to me, that's close! Just picked up a SA-400 Techincs earlier on the bay for $10. Why do I keep getting receivers! I need speakers! haha
     

     

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  12. coreseller

    coreseller New Member

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    Hopefully will get the time next week (3 kids in sports, scouts, etc.) to follow your advice and do the resolder. One question, where did you get the heat sink? I cruised quickly through the local parts express store in Springboro and grabbed some faderlube but did not see any heat sinks. Thanks again.....Mark.
     
  13. markallen

    markallen Luddite Tendencies

    Messages:
    1,144
    Location:
    Bismarck ND
    Regarding the heat sink: I got it off the chassis board of an old computer monitor (where it had been cooling a transistor). I have this "need" to keep old electonics boards around, and sometimes they come in handy to harvest used components. Most old boards have some type of heat sinks, either extruded (like the one in the pic) or cut and machined out of aluminum or steel sheet, often with fluted edges. Old computer power supplies are a good place to look.

    If you don't have access to such useful junk, I have also made heat sinks for this exact application out of sheet aluminum. It can be cut with standard sheet metal shears (aka "tin snips"), so is easy to configure to fit to attach to your existing heat sink. I think it is important to try and extend the life of that overheated transistor, and this is an easy way to do it. At the very least, it can't hurt.
     
  14. coreseller

    coreseller New Member

    Messages:
    24
    Well, I finally got a chance to open up the Pioneer. Funny thing, I replaced the 880 with another one and while all the controls were cleaner sounding it also shut off when turned up near the 9 o'clock plus position. Regarding the repair; used faderlube on all the pots, worked beautifully. I resoldered the suggested transistors, cleaned everything up and hooked it back up, sounds great now up until the 10 to 11 o'clock position and the same thing happens, it shuts off until I turn the volume way down and the audible click occurs and you get sound again. It appears I just raised the threshhold on the volume a bit, any other ideas? Also, I did not put on the heatsink since I have't been able to find any, thanks again.....Mark.
     
  15. markthefixer

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

    Messages:
    21,085
    Location:
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    I don't have a 880 schematic, I have a 780 and a 980. Both use a pa3004 protection integrated circuit, BUT the 980 has extra parts around the pa3004, a zener diode, transistor and what not. So I can't guess what yours has. But the I.C. has simplified the protection circuits in these receivers. (Then they complicated them again in the 980!! and if there are extra parts they could have gone bad)

    BUT you need to monitor the the outputs, for dc voltage. WITH NO SIGNAL,(turn it to aux etc) connect a DMM set for autoranging dc volts to the speaker terminals, and see what it reads. Then WITH NO SIGNAL, turn UP the volume control and see if the relay kicks out and what the meter was reading just before it's disconnected (internally) by the relay.

    There should be almost NO dc voltage. If there isn't and the relay doesn't click than it's the amplified signal that is making something unhappy.

    At this point you will need at least a schematic diagram.

    See the thread by EchoWars about: Amplifier Distortion, DC-Offset, and You! It is a sticky at the top of the vintage solid state forum for an explanation of this DC stuff.
     
  16. coreseller

    coreseller New Member

    Messages:
    24
    Thanks there Mr. Mark. I'll follow your advice there but before proceeding I gotta fess up, I do not even own a voltage meter. Since I've decided to continue with the repair and I'm sure I'll probably have a use for one elsewhere in the future could you please let me know what / where you would suggest I should pick up in the way of a meter? I kind of surprised myself at how easy the soldering thing was (I've watched my brother-in-law closely over the years do electronic repairs for me) and look forward to learning more, thanks again.....Mark.
     

     

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  17. markthefixer

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

    Messages:
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    There have been threads about picking DMM's, and any call for assistance in the general topic forum will get a blizzard of suggestions.

    Thirty bucks at radio shack will do you just fine, but you can probably go down to ten bucks if you look around. You just need to resolve down to 1 millivolt, so a 1 volt range on a 3 1/2 digit meter will read from 0.001 to 1.999 volts.

    You will need to get sx-880 schematic diagrams (online or paper) so a post for help in the pioneer forum may get results.
     
  18. markallen

    markallen Luddite Tendencies

    Messages:
    1,144
    Location:
    Bismarck ND
    Sorry my suggestion for remedy did not work out. Just based my suggestions on what I have seen with my SX-880/890s. Markthefixer has provided some useful information to help me with power supply problems on my SX-980 (mtf, will be posting findings shortly). He clearly knows far more than I (My name is Mark, but in my case it's "Mark[who ASPIRES to be]thefixer"!!).

    If you can't come up with SX-880 schematics a faster way, I have one for the SX-890, same thing. PM me your address and I'll run a copy on the copy machine and mail it.

    The DC offset/bias settings for the 880/890 (from the service manual) can be obtained from this site:

    http://jbmanuals.free.fr/Pioneer/docs-pub/sx-880/

    I saw a DMM in the Sears flyer (Sunday newspaper) for $8.99, normally $20. Have no idea how good it is, says "19 range". But I'm sure they have a variety of others if that one doesn't have the millivolt setting you need. Of course Radio Shack is always an option. I highly recommend getting some mini-clips for whatever DMM you get. Probes are fine for some things, but eventually you'll be getting readings, the probe slips and - POP - you've blown a channel. I recently learned this the hard way. . . this is painful . . I can't talk it about it any more . . .

    markallen
     
  19. markthefixer

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

    Messages:
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    Location:
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    Markallen, good point about the mini-clips.

    Also, the test probes you use should have a sharp point so they don't tend to slip, and all but the tiniest end of the sharp tip should be insulated.

    BTW markallen, my middle name ia allAn, making me a markallan..... :D

    And searching for failed solder joints (usually by heat flexion) on a Pioneer is always time well spent.
     
  20. markallen

    markallen Luddite Tendencies

    Messages:
    1,144
    Location:
    Bismarck ND
    I stopped by Sears today to look at their sale-priced 19 range DMM. Actually doesn't look too bad, does include the 200mV setting. For $9 it's even got the Craftsman label so the warranty should be good. As I expected, Sears has a wide variety of meters to choose from, even sells some Fluke products (much more pricey of course). Whatever, any one with interest in all things electrical/electronic would be well served to start out with such a DMM, should work fine for basic audio diagnostics such as DC offset.

    One thing I noticed is that some of the meters (not the $9 model) say they measure capacitance, I think I saw up to 200 mf. Does this mean you can test some capacitors?
     

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