Onkyo A10 - Power OK, relay click OK, no sound

Discussion in 'DIY' started by paultlaw, Nov 26, 2018.

  1. petehall347

    petehall347 the brandy coffee man Subscriber

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    looks like you need 4 capacitors to make up 2 dual ones . originals 13,000uf x2
     
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  2. reddish75

    reddish75 Active Member

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    The amps is built 'dual mono' for the power amps at least, one transformer feeding a dual can capacitor 13000uf x2 per channel for the power amp.
     
  3. paultlaw

    paultlaw Active Member

    Messages:
    479
    So this means the 2 caps I bought will not work then??? Damn
     
  4. petehall347

    petehall347 the brandy coffee man Subscriber

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    yes .i checked the manual . reddish75 is on the case .
     
  5. ivandezande

    ivandezande Super Member

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    If you bought them from Digikey or Mouser you can return them, they're pretty good about that. Who the heck told you that just two would work?
    I'd use SLPX123M063E9P3 from Digikey. Should be able to fit two of them in each original clamp, making your life much easier. It's fine that they're 12,000uF and not 13,000uF, since the latter doesn't exist anymore.
     
  6. reddish75

    reddish75 Active Member

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    Measure the space you have before buying anything else, you should be able to fit 4 X 35mm diameter caps with there clamps in there, screw terminal caps are the ones I would use
     

     

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  7. paultlaw

    paultlaw Active Member

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    479
    OK thanks for that folks, can someone explain why a single 27k uf cap won't work? I don't doubt you are right at all, why is it that 4 will work and two won't? The dual mono design? So using the 2 caps would mean tying the 2 power supplies together to feed both power amp boards?
    Just trying to understand things a bit better. I do apologise for not being able to grasp things very well
     
  8. paultlaw

    paultlaw Active Member

    Messages:
    479
    Too costly to RMA the caps back to USA, not worth it. Offered them to another ak member who is going to do an a7 resto
     
  9. ivandezande

    ivandezande Super Member

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    Sounds like you got it - there's two transformers. Each is it's own independant power supply. In a amp with just one transformer, it has at minimum two main caps, one for each rail.
    Naturally you need four, two for each transformer.
    And yeah, you could tie it all together but that kinda defeats the purpose of the dual mono design.
     
  10. reddish75

    reddish75 Active Member

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    Yep connecting both supplys together would essentially parallel the supplys.

    Connecting two transformers through one set of capacitors one for negative supply one for positive, this could create channel imbalance as one channels current demand could out strip the other at times and it would also create more cross talk aka noise in both channels and if the voltage didn't match between each transformer and bridge it could create more demand on the higher voltage supply possibly burning it out.
     
  11. paultlaw

    paultlaw Active Member

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    479
    Got to test the amp tonight, after putting in anew relay and putting chassis back together, the onkyo is impressive!

    Did not touch any transistors in the amp.
    Can I please beg some more input on which are trouble makers, I am waiting on a few parts and the power supply is next.

    I'm an onkyo convert now I believe!
     

     

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  12. reddish75

    reddish75 Active Member

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    Here's a good resource for troublesome transistors all the usual suspects are mentioned http://audiokarma.org/forums/index....ilure-prone-whatever-and-replacements.731653/
     
  13. paultlaw

    paultlaw Active Member

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    479
    Thanks for that, I have seen that list already. I kinda want to see if there is a way I can future proof things a bit by getting some stuff to keep, just in case. Lots of transistors in these I'm unfamiliar with. I worry that in a few years there will be parts that cannot be found anymore, nor a suitable alternative available.

    Have not touched any transistors on this so far.
    Protect section of board kicking up some heat, should the resistors in that area be looked at, reason being the metal shield has heat marks from the resistor sitting below it. Think its 330ohm 2w
     
  14. paultlaw

    paultlaw Active Member

    Messages:
    479
    Is it OK to bump up the wattage on the resistors that get pretty hot on the protection board?
     
  15. petehall347

    petehall347 the brandy coffee man Subscriber

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    2w will run hot. higher wattage will run just as hot . keep them up off the board and away from other things if possible .
     
  16. paultlaw

    paultlaw Active Member

    Messages:
    479
    Hi, back again, so recapped bother power amp boards and refreshed heatsink grease and mica. Bias is set to 10mv by connecting across r39 and adjusting r22 to 10mv after half hour.
    Center voltage is 11mv on left and 6mv on right - manual says to cut jumper on left channel given the reading, but i am thinking its so close to 10mv that i will just leave it be. (Supposed to be between 0-10mv) if greater J1 or J2 or both has to be cut but i think its close enough to leave it be.
    There is a 2sa726 on protect board and multiple on the preamp board i will change these to ksa992fbu, also a 2sa720 but i do not have any KSA1013's, ill order some - close her up and i think we are done, with the exception of the filter caps.
    Does that sound ok?
     
    Last edited: Feb 10, 2019

     

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  17. paultlaw

    paultlaw Active Member

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    479
    I am going to refresh the power supply diodes - and if possible looking to beef them up, unit is a 220v we get 230v over here (dont know if that makes a difference at all Tbh).
    Can i get please ask for some help to confirm these are ok subs? If there are better/beefier subs please do let me know, thanks
    1S1555 = 1N4148
    1S1885 = 1N4004
    WZ-250 = 1N5253B

    I'm asking because one of the diodes on protect board is kicking off a lot of heat, it was not the resistor as I initially thought. Its mounted flush to the board
     
    Last edited: Feb 12, 2019
  18. paultlaw

    paultlaw Active Member

    Messages:
    479
    :) Gentle bump
     
  19. reddish75

    reddish75 Active Member

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    216
    Few questions about your ac voltage, mine sits at ~ 252v whichis one of the reasons i didnt refurb the amp, what does yours sit at? Also whats your dc voltage at the output of the big caps?

    All diode subs good to go.
     
  20. paultlaw

    paultlaw Active Member

    Messages:
    479
    Thanks for the greenlight on the diodes.
    I will check the voltages over the weekend, think it was 57v at the filter caps, i may be wrong, not great with this stuff as i am sure you have gathered.
    But all around i was seeing a few volts highers than specified per the manual
    That why i was getting worried about all the power components - would beefing them up be a good idea?

    might not be tonight - Valentines today, need to panic buy a few bits!
     

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