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Does this transformer look normal?

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    #1

    Does this transformer look normal?

    I just opened up a 20 year Sony STR-DE945 receiver a friend asked me to look at, it suddenly no longer will power up. I haven't tested anything yet but stopped when I saw the transformer covered in an amber like substance, just hoping it's normal & not melted enamel from the winding (if that does happen to these). I just thought I ask here before I go any further with this receiver. Everything else looks good, nothing obvious.
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    #2
    Re: Does this transformer look normal?

    That's normal, the transformer was dipped in varnish and vacuum impregnated as part of its construction.
    There would be an internal thermal fuse for the primary protecting it as well.
    I would check continuity at the line cord and work back to see if the on/off switch, main fuse, transformer primary, line voltage selector etc. are ok. There is an open circuit somewhere...

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      #3
      Re: Does this transformer look normal?

      ok, thank you, found out this is normal after I posted message. Now on the hunt for what failed, odd, when plugged in one of the power board relays clicks but none of the others do. No voltage output from transformer. Seems we have a power problem so down the rabbit hole I go.

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        #4
        Re: Does this transformer look normal?

        RY901 must be closed to supply ac to the main transformer, also check fuse F901. There are many fuses in this receiver for the different dc voltages, download the service manual.

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          #5
          Re: Does this transformer look normal?

          I do have the service manual. Thanks for the info. All fuses were good. It ends up that the transformer is bad. No outgoing power, thermal fuse is probably open. Not going to bother digging for the fuse, just getting a replacement transformer.

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            #6
            Re: Does this transformer look normal?

            So you got power going into the transformer And nothing comes out?

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              #7
              Re: Does this transformer look normal?

              Nada. I was fortunate to find a used one in Montreal for $40, waiting on receiving it & hoping it powers the receiver up without any other 'surprises'. The only thing that worked when the unit was plugged in was the standby relay but that is powered separately. I guess I could try to dig out the fuse but my understanding was that if the thermal fuse tripped then the winding may be in bad shape as well, so better to replace it and hope I get one that lasts a few months.

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                #8
                Re: Does this transformer look normal?

                I would check if it has a thermal fuse, if it does you can just install a thin wire or use a couple amp fuse to check it, If it works, replace it with the correct thermal fuse and it should be ok.

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                  #9
                  Re: Does this transformer look normal?

                  Well, I'm in the process of digging it out. In the interim, I've replaced the transformer and all is working again - for now. I was able to get the receiver back to the customer in short order. So far, wow that fuse is really buried, still peeling the 'onion' back as time permits. I know it's gotta be in there somewhere.

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                    #10
                    Re: Does this transformer look normal?

                    Originally posted by repair-it View Post
                    Well, I'm in the process of digging it out. In the interim, I've replaced the transformer and all is working again - for now. I was able to get the receiver back to the customer in short order. So far, wow that fuse is really buried, still peeling the 'onion' back as time permits. I know it's gotta be in there somewhere.
                    sometimes you find the wires before the fuse and can stop right there .

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