Yamaha RX-V371

Discussion in 'General Electronics Chat' started by Ballistic, May 10, 2015.

  1. Ballistic

    Thread Starter New Member

    May 10, 2015
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    Hello guys, my second post, and the main reason for me joining the forum. I'm hoping someone could assist me with this issue.

    I just got a Yamaha RX-V371 receiver from a friend, unit initially taken so I could strip it for spares. But, but....... it just looks so nice, and new! It was imported unit that he brought in from the States. He plugged it in not knowing that it was a 110v unit, and here in South Africa we use 220v.

    And! Unit DEAD! Now I'm no electrical engineer, but neither a total idiot :) So today I checked the resistance on the standby transformer primary and i get no reading at all, secondary seems fine, and so does the main transformer, so at least that is okay, I hope. My question is, what else could have gone on the unit by plugging it into the supply? And is it possible to get a replacement standby transformer for it?

    Thank you and have a great day.

    Regard
    Cedric
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,053
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    Is there a fuse anywhere in the primary circuit?
     
  3. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Lots of things might have happened.... from a blown fuse to a burnt primary. I suggest you post some pics
     
  4. Ballistic

    Thread Starter New Member

    May 10, 2015
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    Forgot to mention, the fuse tested with a meter and it's fine. As for pics, should I upload some pics of the standby pcb?
     
  5. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    Load pics from the top and the underside of the PCB
     
  6. Ballistic

    Thread Starter New Member

    May 10, 2015
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    coming! :)
     
  7. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    get the back off and test the voltages to and from the transformer...
     
  8. Ballistic

    Thread Starter New Member

    May 10, 2015
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    Pics as requested

    [​IMG]

    [​IMG]

    [​IMG]
     
  9. Ballistic

    Thread Starter New Member

    May 10, 2015
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    Gonna be a problem, the unit is 110v and here in SA we at 220v. Gonna see if I can get a step down convertor at work tomorrow and check it out.

    This unit is literally brand new, so would really like to get it going. I also have a working RX-V361. Older unit but looks almost the same, quite tempted to yank the transformer pcb out there and sticking it in this newer unit.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    A standby transformer will usually have a thermal fuse embedded in the primary winding. The fusible wire is very thin, so proably blew because of excessive current.

    Sometimes you can expose the thermal fuse without digging into the winding - if you can get hold of an autotransformer with the correct output voltage, its worth temporarily linking the fuse so you can verify the correct secondary voltage to order.

    For the main PSU, sometimes you can get lucky if its a SMPSU - the chopper transistor can blow before much damage happens downstream.

    Linear supplies generally take longer for something to heat up and melt - by which time a pair of output transistors could punch through or multiple damage all the way through!

    You could be lucky and the bridge rectifier died first and took out a fuse.
     
    cmartinez likes this.
  11. Ballistic

    Thread Starter New Member

    May 10, 2015
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    Funny you should mention that, I watched a Youtube video regarding that. Will check it out now.
     
  12. Ballistic

    Thread Starter New Member

    May 10, 2015
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    Okay, cut open the standby transformer on the primary side, and found the neutral wires was broken. Might be this, but will have to check tomorrow. That wire is very thin for 110v. Literally like a hair.
     
  13. cmartinez

    AAC Fanatic!

    Jan 17, 2007
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    It would be nice if you could post a pic of that as well
     
  14. Ballistic

    Thread Starter New Member

    May 10, 2015
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    Update, soldered the neutral wire back on, no resistance or continuity. So I guess it must be further down the winding :-(

    Here is a pic of it cut open. More like butchered it open :)

    [​IMG]
     
  15. ian field

    Distinguished Member

    Oct 27, 2012
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    And once the secondary voltage can be ascertained - it should be binned - it would be a bad idea trying to get any further use out of it.
     
  16. ian field

    Distinguished Member

    Oct 27, 2012
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    That looks more like a regular power transformer to me - sure you checked the primary where its leads solder to the board? - If you checked at the pins of the connector that eventually get there, you might have included a fuse and the relay contacts in the test.

    Still, if the primary is the wrong voltage anyway, it has to be replaced.

    You'll need to look at the design tables for capacitor input PSUs to guesstimate what secondary voltage to order, from the rectifier/reservoir ratings.
     
  17. Ballistic

    Thread Starter New Member

    May 10, 2015
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    Yes I am sure, straight into the board from the transformer, noting in between. Mains in to tha standby transformer and from that same point the live goes into the fuse and a few other components.
     
  18. Ballistic

    Thread Starter New Member

    May 10, 2015
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    It's late, gonna take a look at this tomorrow again. Thank you to everybody for the replies and trying to assist.

    It's much appreciated.

    Regards
    Cedric
     
  19. Ballistic

    Thread Starter New Member

    May 10, 2015
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    Just a bit of an update, was in contact with the Yamaha agents of South Africa today, looks promising. They might be able to assist me with parts, especially the standby transformer. For now, just need to get it to switch on.
     
  20. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    If it does not have a 220VAC setting, Switch it on with a 220V stby Tx and you will blow the main TX, If you are lucky the smoothing caps might survive.
     
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