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Transformer Hi, Our amp does not power up anymore. According to a professional it is the transformer. Anyone know if and where these are for sale?

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  • Ruud Zijlmans Feb 16, 2008

    Hi Graeme,



    Thank you for your reply.

    We are located in Scotland, United Kingdom.

    The amp is Sherwood Newcastle R-925RDS the numbers on the transformer are: R-925

    8200-28101-636-0

    YK-81110



    Regards,



    Ruud






  • Ruud Zijlmans Feb 16, 2008

    We had a professional repairman testing the amp this morning and he came to the concludion that the transformer is dead.



    well... I can solder a bit, do know my way with a skrewdriver but unfortunately do not have a multimeter.

    I'm ready :)

  • Ruud Zijlmans Feb 16, 2008

    I'd say we have a go at repairing the transformer first.



    No problem, I can get a multimeter, however that will have to wait till tomorrow as it's nearly midnight here.

    I'll mail you tomorrow as soon as I have the multimeter, ok?



    Ruud

  • Ruud Zijlmans Feb 17, 2008

    Hi Graeme,



    Got the multimeter. Probably need some help with that too :(

    Ready when you are :)

  • Ruud Zijlmans Feb 19, 2008

    Hi Graeme,



    I think I have the difficult one :(

    Here's the pic

    I have removed the bracket and the copper band that went over the blue plastic.

  • Graeme Ross
    Graeme Ross May 11, 2010

    Hi there,

    Transformers are generally available as OEM parts from the manufacturer or distributor of same. If you could tell me where you are located and most importantly, the MAKE and MODEL then I can find a part number and a supplier near to you. Some transformers can also be repaired. Waiting your reply.



    regards

    Graeme

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  • 1,512 Answers

Hi Ruud

How electronics savvy are you... have searched for a parts supplier outside of the US, and ... still searching. I can give you a fix for the transformer if indeed that is what is the problem:) Need you to be able to solder and be handy with a screwdriver, and perhaps have a basic multimeter handy... are you ready? :)

Posted on Feb 16, 2008

  • 1 more comment 
  • Graeme Ross
    Graeme Ross Feb 16, 2008

    Welling Australia is the Sherwood Distributor here in Australia.... have been for years, but I gave up on dealing with them when I was a Sherwood agent years ago... took forever to get anything from them...




    1. I could do a Price and Availability from them to see if I can get the part for you. They are not too hard to change, and you could do it yourself.

    2. Or..... we can have a go at repairing the transformer.... but first, you really need to get a cheapo multimeter.... cost you less than $10 from an electronics hobby store these days.

    regards

    Graeme

  • Graeme Ross
    Graeme Ross Feb 19, 2008

    OK, few steps to get there:) i am going to talk you through a visual way of checking the internal thermal fuse in the power transformer


    1. Disconnect unit from the mains

    2. First check for the obvious, an overlooked blown fuse. Check them with your multimeter set to the x1 ohms range.

    It should read less than 1 ohm!! Sometimes fuses can look ok, but actually be faulty. Replace any blown fuse if you find one with the same type and rating. Fire it up again if you find and replace any blown fuse, Otherwise....


    1. Identify the mains power transformer. It is the biggest and heaviest component in the unit.

    2. Inspect the transformer, see if you can spot 2 rows of thick tin plated copper square shaped (about 1x1mm) mounting pegs/terminals that connect the rest of the amp to the transformers internals via single core enamal coated copper wires generally wirewrapped about these same square wire pegs. The primary circuit(mains side) is the thinnest copper wires.

    3. If you cant get into a position to see these terminations, you may have to remove the transformer to get a better look. Don't be afraid to clip any cable ties that have been used to tidy up any excess wiring to the transformer

    4. Look for a pair of tinned copper wires(not enameled copper) connecting to these same wirewrap posts. The same posts will also have a rather thin ennameled copper wire connected to it.

    5. This is the thermal fuse that has probably failed.

    6. Check this for continuity with your ohms meter to read zero ohms.

    If it is open circuit(reads nothing)... then this is why your amp has stopped. You will need to jumper this internal thermal fuse and the amp will work again. Once you have identified which external connections of the transformer are wired to the internal fuse, you can do it from the outside of the transformer on the connection pegs. The thermal fuse is there to satisfy an American mains standard, that we dont need with the MEN system that is used, so no harm comes from jumpering it



    If you are unlucky, the transformer will have the wiring going straight into it, and you may have to actually carefully cut your way into it to find the thermal fuse and then jumper it. The thermal is always mounted on the outside of the windings, but may be under a few layers of tape, plastic, and sometimes a copper band. these are a bit harder to fix, and often you may have to remove the transformer to get access to it. If you think its going to be a difficult one, stop before you start and see if you can find an electrically savvy mate to help you.



    or



    post a picture of it in here and I can assist you directly. Bit limited doing this in here... but I reckon we can do it :) Good Luck



    regards

    Graeme

  • Graeme Ross
    Graeme Ross Feb 19, 2008

    hehehe wow that was quick

    bed time here in Aussieland..

    my wife made me come send you this note... more tommorrow:)

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