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Pioneer SA-505 clicking

Discussion in 'Audio' started by tooter, Feb 17, 2018.

  1. tooter

    tooter

    36
    1
    Feb 17, 2018
    Hi all new to this forum hoping for some help with me trusty amp. just lately it stopped clicking when tuned on and no sound came out indicating the relay not activating it was intermittent. ive had a go at trouble shooting but now hit the extent of my knowledge.
    What a have done so far.
    removed the relay and tested continuity. OK
    tested the actuator with a separate psu clicks as it should
    removed the power transistors. tested with a mm all seems ok. (but im no expert used a guide on youtube to test)
    then i tested the voltage on the board across the pins where the relay actuator lives and I get 48v which i found strange as the relay clearly states 24v. idont know where to go from here any input would be great full. thanks.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    Pictures would be a good start, as would be an indication of where you are reading the voltage (and with respect to what).

    Also, if you could briefly describe the tests you did on the transistors, whether you removed them form the circuit to test them, and the part numbers of the transistors (if not clearly visible on you photos).
     
  3. tooter

    tooter

    36
    1
    Feb 17, 2018
    Hi first of all thanks for taking the time to reply. I will do my best to give you a clear picture of what i have done so far.
    1) Removed all 4 power tranys and tested using this guide.
    https://vetco.net/blog/test-a-transistor-with-a-multi meter/2017-05-04-12-25-37-07
    (
    trany part no 2x A1104 2x C2679
    data sheet if it helps https://www.semicon-data.com/transistor/tc/c0/C2679.html
    https://www.semicon-data.com/transistor/tc/a0/A1104.html



    Transistors.jpg
    2) remvoved relay tested with a 20v power supply. click down as it should making the circuit across the terminals. I removed the cover to test the mechanical workings.

    relay cobbver removed.jpg

    3) tested the voltage where the relay sits and it was 48v.
    underside pcb.jpg underside relay removed.jpg
    hope ths helps clear things up a bit,
     
    Last edited: Feb 18, 2018
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    It seems that the two pads highlighted are the ones used to energised the coil.

    If you replace the relay, what does the voltage across these points read? My suspicion is that it will be 0, or very close to it.
     
  5. tooter

    tooter

    36
    1
    Feb 17, 2018
    Hi it measures 6v
    Just had the nasty realisation that i may have put the tranys back in the wrong place didnt even notice they was different when i removed them.
     
    Last edited: Feb 18, 2018
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    Did you take a photo before you too things apart?

    When you tested the transistors, were they a combination of PNP and NPN?

    Hopefully the relay not pulling in has helped protect the transistors.
     
  7. tooter

    tooter

    36
    1
    Feb 17, 2018
    No didn't take any pics before.
    Don't know if the was mixed or not.
    Is there a usual configuration for them? How can I find out?
    Could I have damaged something else by putting them in wrong?
    I'm so mad with myself for not taking a pic first school boy error.
     
  8. duke37

    duke37

    5,226
    718
    Jan 9, 2011
    Find out if they are npn or pnp by looking at the number or testing on a transistor tester. The tester will also tell the correct connections.

    Get a schematic (circuit diagram) to see what is connected where. It depends on the circuit as to what could be damaged.
     
  9. tooter

    tooter

    36
    1
    Feb 17, 2018
    OK thanks for the answers for the time being I have removed the the tranys from the curcit can I carry on troubleshooting the original problem now or do I need the fix the trany problem first?.
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    When you originally tested the transistors the instructions told you how to distinguish NPN from PNP.

    I haven't been able to note the part numbers of those transistors because I'm using my phone. If they're not all the same then it's going to be non trivial to find out which one went where.

    Finding a schematic would be really useful.
     
  11. tooter

    tooter

    36
    1
    Feb 17, 2018
    Hi thanks looking for schematic for it now hopefully I'll have a bit of luck. Kicking myself at the mo.
     
  12. duke37

    duke37

    5,226
    718
    Jan 9, 2011
    You give links to C2679 transistor and A1104.
    The 2C2679 is a npn very high frequency transistor in the small TO-92 package. 19V 50mA.This is unlikely to be used in an amplifier, it would be used in a VHF radio.
    The 2SA1104 is a power transistor (120V 5A) in a TO-3P package and would be fixed to a heat sink. If you have two of these, there should be another two npn transistors in a similar package fixed to the same heat sink for stereo.
    With no load, the amplifier may work on just the driver transistors. Adding a speaker load will pop these off.

    I would not put the transistors back in until you know where they should go.
    Do not remove anything else until you know where the fault is. I think you will now need an expert willing to spend considerable time on this to find the original fault and the extra faults you have added. I would not fiddle with it without a schematic.

    The relay connection could have been tested by closing it manually. If the amplifier then worked, the fault was in the relay drive circuit. 6V on a 24V relay would not be enough to pull it in.

    What is an actuator?
    Where are you?
     
  13. duke37

    duke37

    5,226
    718
    Jan 9, 2011
    It looks as if you can get a servicing manual down load for $17 from servicemanuals.net.
     
  14. tooter

    tooter

    36
    1
    Feb 17, 2018
    Hi thanks. There was 4 transistors connected to the heat sink. (See pic) they are the ones I removed in the links. By actuator I ment the coil that activates the relay. I'm in the UK . may have to get the manual would like a free one really as the amp is more sentimental the cost as it was a 18 bday prezzie.
     
  15. duke37

    duke37

    5,226
    718
    Jan 9, 2011
    I think that you have the 2SA1104 correct but the other two will not be 2SC2679. What is the correct type number?

    I see that you are in the UK but this is quite large. You could be in Stornoway or Pensance. I was wondering how far from mid Derbyshire.
     
  16. tooter

    tooter

    36
    1
    Feb 17, 2018
    Hi looks like i got lucky today. i found the service manual for my amp the manual is for the sa-540 not the sa-505 but it is identical. im having trouble reading it though. I believe I hve identified the layout of the power tranys which i will test again before i replace hopefully we can move forward and solve my problem attached is a link to the manual.
    https://www.dropbox.com/preview/Shared/hfe_pioneer_sa-540_service_arp-304-0_en.pdf?role=personal
     
  17. 73's de Edd

    73's de Edd

    2,684
    1,088
    Aug 21, 2015
    Sir tooter . . .

    I am sure that you can see by now, by referencing, that the PNP 2SA1104 transistors go to the center of the set of 4 and the NPN 2SC2579 are being the extreme outer units in the physical layout on their heatsink..
    The explanation for the ASR1107 24VDC relay and the 48VDC supply, is that the + 48VDC is the higher voltage supply voltage that the POWER transistors use . . . then they have an 820 ohm 1 watt voltage dropping resistor to drop that higher voltage down to the 24VDC power for the relays coil.

    73's de Edd
    .....
     
  18. tooter

    tooter

    36
    1
    Feb 17, 2018
    Hi am it turns out I had the tranys in the right place after all. As you can see from the pics above they are from after I removed them the first time so happy days. But I still have my original problem. Would really appreciate any further help on diagnosing the problem from here.
     
  19. tooter

    tooter

    36
    1
    Feb 17, 2018
    Hi thanks after replacing the relay I can only measure 6v across the relay. Any further help would be appreciated. Thanks
     
  20. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,693
    Jan 21, 2010
    The previous advice was to manually operate the relay and see what happens.

    The relay is almost certainly part of a protection circuit. It is either failing to actuate because the circuit detects a fault, or because the protection circuit is faulty.

    In the latter case, actuating the relay will cause the amplifier to operate normally.

    In the former, you might see smoke.

    I don't have the schematic, so I don't really know what the relay is doing. It may be part of a complex circuit that checks various parameters, or it might just rely on the main power rail, disabling the output when it is not in spec.
     
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