Pioneer SX-980 Protection Relay Kicking Out

Discussion in 'Pioneer Audio' started by Brivan, Aug 16, 2018.

  1. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    Hi, folks

    I've read a number of threads dealing with the protection relay not engaging in a Pioneer SX-980 receiver, but nothing regarding the relay dropping out right after turning on. I assume I've got amplifier issues, but not sure where to logically start. Using the service manual, I did reset the amp board pots to home position for the calibration. I can't even begin to set them due to the protection relay kicking in and out. Any ideas of where to start would be appreciated.

    Thanks!

    Brian.
     

     

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  2. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    Well, apparently Audiokarma wiped out several replies to my message above. I noticed on Friday the website was having issues - looks like I was an innocent victim.

    One of the lasts posts I received was from Merlynski advising that I remove Q1 from the protection board and measure voltages on the PA3004 IC. I've done that, and my protection relay is still cycling on and off, with the off state lasting about 3 seconds, then very briefly on, then right back off for 3 seconds.....and the cycle continues. With that, I don't know how accurate my voltage readings are. Here's what I got:
    Pin 1 +13.44vdc
    Pin 2 N/A
    Pin 3 0v when relay is off; maybe around.25vdc when relay is on briefly
    Pin 4 +.013vdc
    Pin 5 0v
    Pin 6 -7.5vdc
    Pin 7 .64vac
    Pin 8 +1.5 ~ +5.5vdc (depending on the charge state of the timer cap, I'm guessing)

    Thanks and I hope you pick this thread back up again!
     
    Last edited: Aug 20, 2018
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  3. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    Since Q2 on the protection board seems to be a common-failure item (according to other posts), I went ahead and replaced it with a Digikey 2N4401 transistor from some stock I had in the shop. It cross-referenced to an NTE123AP - same as the original 2SC1438. Still getting the cycling protection relay (with Q1 still removed) - same as before. Starting to wonder if the IC is bad.....
     
  4. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    I also replaced Q1 with an NTE290A, which is a direct NTE cross for the original transistor. Still have the same problem. As noted in a now-deleted post, all the caps on the protection board have been replaced. Diodes all tested okay.

    The receiver worked great prior to me bringing it into my shop for a cleaning, LED upgrade and cabinet repair. As noted in a now-deleted post, I pulled the boards containing the toggle switches and control pots in order to gain better access to them for spraying in DeOxit. The two boards were pulled back just enough to get the switches and pots clear so I could turn them enough for cleaning access. The receiver was gently blown out with compressed air, then I reassembled the boards and the faceplate. That's when I discovered my relay in-and-out problem.
     
  5. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    Here are the voltages from the protection board:

    Pin 1 19.79vac
    Pin 2 -52.7vdc
    Pin 3 0v
    Pin 4 13.13vdc (creepy)
    Pin 5 0v
    Pin 6 -.08vdc
    Pin 7 -.1vdc
    Pin 8 0v
    Pin 9 13.39vdc
    Pin 10 66.9vdc
     
  6. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    402
    Location:
    High Plains, Eastern Colorado
    I am back from my trip, my son got married.
    Apparently AK had server issues and restored from backup. :biggrin: Let us begin again :bigok:.
    My schematic copy was smudged and I saw "Q1" where I really should have seen Q2. I have taken a better look at the schematic and I apologize for the error. I really meant for you to pull Q2 and then power up with it out. This should stop the relay from cycling and allow for a more steady state troubleshooting process. Pin one of the IC should be +13vdc, that is connected directly to pin 16 of the power supply assembly, and is the 13v supply for many parts of the amp, so that looks good as you reported . I think the list of voltages on the protection board looks acceptable.
    As a suggestion do not cross reference with information from NTE. They seem to try to cross ref as many transistors as possible to sell as many transistors as possible, rather than finding the best match. Recommendations from markthefixer or echowars are good choices. There are quite a few others. Also dlucy has an excellent transistor sub thread he is maintaining with input from AK people: http://audiokarma.org/forums/index....ilure-prone-whatever-and-replacements.731653/

    EDITS: for clarity
     
    Last edited: Aug 21, 2018

     

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  7. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    402
    Location:
    High Plains, Eastern Colorado
  8. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    402
    Location:
    High Plains, Eastern Colorado
  9. slipstream55

    slipstream55 Active Member

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    235
    Location:
    Gilbert, Arizona
    I have all of the posts on this thread thru #13 if you want them back.
     
  10. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    402
    Location:
    High Plains, Eastern Colorado
    I will let the OP decide, I'm good the way it is though. Thanks Much! How do you save them?
     
  11. slipstream55

    slipstream55 Active Member

    Messages:
    235
    Location:
    Gilbert, Arizona
    Don't laugh...

    I'm am working on a never-ending project. Years ago, shortly after I joined AK, I created a word doc for each piece of audio equipment I owned or hoped to own. The list is extensive. In those word docs I copied/pasted every AK thread (posts and pics) that related to technical info or troubleshooting for that piece of equipment. The ultimate goal was to have a troubleshooting document when ever I needed it that could be easily searched or used off-line in the event AK was down or in this case, lost info. The effort has paid off more than once. Since I was doing a lot of business travel at that time, it was also a time killer on boring week-ends. Like I said, I have been at this for a long time and it will never be completed but it has been useful.
     
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  12. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    Thanks for the offer! I'll work with Merlynski on this for the time-being, but I'll keep you in mind!
     
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  13. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    402
    Location:
    High Plains, Eastern Colorado
    OK! Since having Q1 out did not stop the relay cycling that indicates that the problem is not coming in through the overload detection.
    Is Q2 on the protection board out? Does having it removed stop the relay cycling?
    Report the voltages on the pins of Q3 again please. Is pin 3 near +13 vdc or near 0 vdc, or doing something else?
    What is the voltage at the collector of where Q2 shoud be? I am expecting about +65 vdc.
    Measure the pins of the protection board again please, if the relay stopped cycling..
     
  14. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    First off, sorry for my delayed response - I was on vacation last week, so my first day-and-a-half back were occupied by playing catch-up. After reading through some of the linked threads on the subject of the PA3004 IC, I thought it would be a good idea to ohm out the power resistors on the protection board. They checked okay, so I decided to power the receiver up to see if anything had changed after sitting for a week. Surprisingly it did! The protection relay still cycled off and on, but it stayed on longer than before - and the duration of the on-time changed from a half-second to maybe two seconds. This got me to thinking about crappy connections, so I had another look at the solder connections on the board, but everything looked good. I then used my tweaker to push on different components while the relay cycled. When I got to the IC, the relay stayed on when I pushed on it. Well, how about that? I resoldered all the pins of the IC and now I have an operational receiver!

    Thanks you for all your help with this and I'd be more than happy to report any follow-up voltages to you for the purpose of "closure". That IC is so small, it's hard to imagine any of the solder points coming loose - they all looked fine. So I'm wondering if the IC itself was a little flunky internally. And will I have this problem sometime again in the future? Time will tell, I guess.
     
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  15. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    402
    Location:
    High Plains, Eastern Colorado
    You are welcome, glad I could help. 'Closure' readings not necessary, but thanks!
    Time and temp change will cause marginal solder connections to flake out. Glad you got it resolved, and that we were looking in the right area :).
     
  16. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    Well, I guess I spoke too soon. I came back from salvaging some Klipsch Cornwall II speakers that were going to be thrown out and powered up the receiver - it's back to cycling the relay again. Pushing on the PA3004 IC stops the cycling and the receiver works normally. I'm guessing my IC is flaky?
     

     

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  17. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    402
    Location:
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    Or maybe a cracked trace nearby, look really close with a magnifier, and/or scrub off the soldermask nearby and flow over the trace with solder. Might be the chip cracked internally :(. Cheapest replacement is about $12, on the fleabay from China, purportedly an OEM NOS :dunno:
    EDIT: more info
     
    Last edited: Aug 28, 2018
  18. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    Upon even more investigation, I realized I was pushing on the relay when I was pushing on other components - I have the protection board flipped up with the relay against a part of the framework. I just resoldered the relay (makes more sense that it's loose) and it's working every time I turn it on. If nothing else, I'm getting it narrowed down, I think.

    I like that this thread is coming to a resolve - so many I read just drop off and you never hear from the OP about what was done to alleviate the problem.
     
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  19. Brivan

    Brivan Active Member

    Messages:
    108
    Location:
    Sioux Falls, SD
    The gift that keeps on giving......powered the receiver off/on many times while I cleaned the control knobs and put them back on. Last knob to go on was the balance knob. As I did with all the others, I ran it from end-to-end to check for proper position, and that's when the relay starting clicking in and out again. No amount of pushing on protection board components corrected it this time. At the time, I had speakers connected, preamp in/out jumpers in place and sound being fed to the auxiliary input. Disconnecting everything again makes no difference. I guess my biggest red flag is that adjusting the balance pot triggered the cycling of the relay again. It's like moving the balance pot permanently skewed something in the amplifier section since I still have the relay cycling problem even with the preamp in/out jumpers removed. I'll check idle and offset tomorrow - enough for today!
     
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  20. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
    402
    Location:
    High Plains, Eastern Colorado
    Look for a pinched wire caused by the disassemble and reassemble process. One that is barely pinched or pierced and sometimes makes contact may be your demon . . .
    If pre-out power-in jumpers are uninstalled the problem cannot be in the circuitry before them.
    This is getting very interesting :confused:
     

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