Pioneer SX-850 No relay click

Discussion in 'Pioneer Audio' started by jwallace2011, Feb 28, 2011.

  1. jwallace2011

    jwallace2011 New Member

    Messages:
    5
    Hello,

    My name is Justin and I'm a band director. I was cleaning out the attic of our band hall and came across an old Pioneer SX-850 stereo receiver. I plugged it in, and unfortunately, I got no sound. All the lights work, but no sound. Actually, one day I plugged it in and the relay clicked and all was well, but I bumped something in the back (power cable?) and the sound went off again.

    So... I started looking through your forums here and followed some of the steps outlined in similar situations; I removed the top and bottom covers and took some readings with a multimeter on the power supply board. There were some discrepancies:

    pin 6, 7: 49.6
    pin 8, 9, 10: -00.7 (supposed to be 36.5)
    pin 11: 0.1 (supposed to be 28)
    pin 13: -13.3
    pin 14: -51.8
    pin 15: -19.4

    I'm an amateur, and not sure where to go from here. Any help would be greatly appreciated, as this would be a very useful piece of equipment to have around the band hall!

    Thanks,
    Justin
     

     

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  2. sregor

    sregor AK Subscriber Subscriber

    Messages:
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    Hopefully, it is straight forward. Check r5 (150 ohm) resistor on the power supply board. Problem most likely is Q5 open, or r5 open. Also look for bad solder connections in the general area of the transistor. Transistor is 2sc1318 - MTF (Mark the fixer - resident AK pioneer guru) recommends KSC2073 transistor - available from mouser part 512-KSC2073TU. Good luck with it. Steve
    BTW, welcome to AK

    One more tip - make sure basing is correct if you change the transistor. The center lead on both these transistors is the collector. Since it is an NPN transistor, the transistors will conduct from the base to the collector and emitter on diode check. Lets you quickly identify base, collector, and emitter.
     
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  3. Rapidroy

    Rapidroy Well-Known Member

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    Location:
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    it should be 2sc1318, ksc2383, mouser # ksc2383ybu. I think Segor was looking at a SX-950. I'm working on the same problem on mine.
     
  4. sregor

    sregor AK Subscriber Subscriber

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    Location:
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    You're right, but its not an issue - he used the higher power substitute on the 950 because slightly higher power dissipation. It's just a regulator circuit, so either sub will work as long as they fit. Same board and schematic.
     
  5. markthefixer

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

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    I hope that by this point you have downloaded a service manual.

    You are doing nicely, most likely Q5 has died, it is a common occurrence - the transistor is overworked for it's size. The replacement I have specified in other threads is a larger cased transistor that will shed the extra heat more effectively - at a price of maybe having to enlarge the holes the transistor leads fit into slightly to get them to fit.

    The MOST IMPORTANT thing is to get the correct lead into the correct hole - there are six possible combinations of which only one is correct. The guys should find and link to my explanations of the transistor symbol printed on the board.

    edit: this will help a little, read at least the first page of posts, there are useful diagrams:
    http://www.audiokarma.org/forums/showthread.php?t=43186
    this is a load of reading, especially with the links, but is does cover a lot:
    http://www.audiokarma.org/forums/showthread.php?t=331932&highlight=symbol&page=5


    Q5 is (the larger packaged):
    AWR-101: Q5 2SC1318 ecb
    512-KSC2690AYS to-126 ecb 120/a160 1.2a 20w 155mhz 35-320hfe $0.40

    or it could be (the SMALLER packaged):
    512-KSC2383YBU to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

    both numbers are from mouser.com, and the extra data is to assist if you try to obtain the transistor or an equivalent locally. Preferably NOT NTE (long story).

    You will notice they both are ECB layout. the guys should explain... that is with the lettering facing you, leads pointing down, going left to right. The original 2sc1318 is also ecb, but we can't trust that blindly. We use the symbol on the board to designate which lead goes into which hole.

    Now, there is a small chance that Q5 won't get it going (don't worry about pin 11's 28v, that 28v depends upon 8.9,10's +36.5 volts being present. That 28v only runs the phono amplifier section). Then either R6 or C18 is at fault. The big parts list (costing under $15 iiac) does list C18, but not R6. But I can come back with a part number for R6, if needed.

    (You could rebuild the board from that list, ensuring a higher level of reliability.)

    Upon the chance that Q5 replacement does not restore the +36.5v (+/- 10 percent) then voltage reading from the three Q5 leads will be needed to locate less probable reasons for the failure.
     
    Last edited: Mar 1, 2011
  6. jwallace2011

    jwallace2011 New Member

    Messages:
    5
    Thanks to all for such speedy responses!

    Markthefixer, I read through the links you included (even some of the wikipedia entry on transistors). Just one question before I start desoldering: what is Q5? I have the service manual, and I know where it is, but I want to make sure. On the attached pic I've circled in yellow what I believe to be Q5. Could you confirm/deny this?

    Thanks!
     

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  7. markthefixer

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

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    That is Q7..

    Look at pins 4 and 5, to the side of them (closer to 6 & 7) is the Q1 "D313".

    On the other side of the metal heat sink Q1 is mounted on, lined up with pins 4 and 5 are two 2sc1318 transistors. the one closer to the heat sink is Q5, the further one is Q3 if you go further you will run into a light blue capacitor.
     
  8. jwallace2011

    jwallace2011 New Member

    Messages:
    5
    Warm or cold?
    I'm going off the photo now: the receiver's at school.
     

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  9. markthefixer

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

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    bingo
     
  10. jwallace2011

    jwallace2011 New Member

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  11. markthefixer

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

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    Yes, that is it...

    and hopefully after it is replaced, no other faults are revealed. We could do some preemptive replacements, mainly in the protection circuit.
     

     

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  12. jwallace2011

    jwallace2011 New Member

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    Update!

    I know it's been a while... After spring break everything's busy until the end of school.

    Just wanted to let y'all know that replacing Q5 worked like a charm! I used the larger packaged replacement markthefixer suggested from mouser.com. Soldered it in, matching the diagram on the board, tested, and the relay clicked on. It's now several weeks past, and everything is working fine.

    Thanks alot for everyone's help! I'll be checking AK's forums periodically as new projects crop up!
     
  13. chicks

    chicks Lunatic Member

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    That's great! It's a really nice receiver, mine had the exact same issue, searched and found MarkTheFixer's threads here. I wonder how many of these wound up being trashed over the years due to this design problem?
     
  14. markthefixer

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

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    I shudder to think about it..

    I can't rescue them all, but ePrey and greed IS helping preserve them. See their value and think " I can ge some MONEY.." it isn't till later they realize "I've got to PACK and SHIP that thing........"
     
  15. Sir.Byrd

    Sir.Byrd Lunatic Member

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    Over spring break you should recap the whole receiver, or at least the power supply. I see some shrunk cap casings (sign of heat over time), and now that you have it working you can go right ahead and do it all as preventative maintenance.
     
  16. JohnDoe99

    JohnDoe99 New Member

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    Last edited: Mar 2, 2014

     

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  17. JohnDoe99

    JohnDoe99 New Member

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  18. JohnDoe99

    JohnDoe99 New Member

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  19. Watthour

    Watthour Electron Rancher - JS3600

    KT - I think this may have been lost in the old thread. It may be better to begin a new thread specific to your problem and let the 2011 thread fade away.

    A PM note to a moderator might help as they can move/merge posts (or entire threads).
     
  20. markthefixer

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

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    q3 and zd1 are blown, that happens with too high of a load.

    Too high of a load CAN (not the only thing, but likely until proven otherwise) be caused by a mis-installed q5.

    So Q5 needs to be checked.

    Overall you are using old lists iiac, because I had been recommending ksc2690 to-126 transistors for q5 because of the heat it produces.

    Thing is, you may have taken out some resistors, so there is a LOT of checking to do before you EVER apply power again to this unit.

    You are starting into the nightmare of an online piecemeal repair (which usually damages more than it fixes), and I must nip this in the bud, before you spend FAR more on multiple shipping charges than you would on a single parts order for all the transistors and diodes and caps and a few resistors to redo the entire board.

    First, the ksc2383 and the ksc2690 BOTH have ECB layouts, emitter, collector, base from left to right when the lettering is facing you and the leads are pointing down. Refresh your memory about the two transistor symbols (pnp and npn) and how they signify the leads, as these symbols are printed on the board in the center of the lead triangle for each transistor.

    NEVER ** EVER ..... NEVER ** EVER .... NEVER ** EVER ..... use the original transistor insertion alignment for anything other than verifying the OLD transistor's leads, and if the MANUAL disagrees with the ORIGINAL transistor that's on the board, the BOARD is right. Pioneer may blow capacitor polarity markings, but they never (in my knowledge) ever blew a transistor symbol.

    for new transistors (that I specify) there is always a datasheet to be found and downloaded (mouser usually has links) to use for lead identification. I also ALWAYS test each transistor before insertion. I haven't YET found a bad new one, but there's always a first time.
     

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