Baffled by step down transformer choices... Some guidance much appreciated.

Discussion in 'Power Electronics' started by Tommy Sanders, Aug 31, 2016.

  1. Tommy Sanders

    Thread Starter New Member

    Aug 31, 2016
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    0
    I've come here to look for some help in understanding how step down transformers work and which one is right for my needs.

    I live in the UK and have imported a little old American guitar amp from the 60s - 110v. (Kalamazaoo model one)

    here is some more information on the amplifier:

    '110-120v, 60 cycles, .35amps'

    I also know that it was sold as a 5W amp, so not very powerful.

    I can see that there are a vast array of transformers available; i'm keen to understand which one is right for this amp, so that I don't end up damaging it!

    If anyone could explain this to me, I'd be really grateful as I can't wait to play the amp.

    thanks guys
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    The transformer in your amplifier may be distressed by UK 50Hz mains as it was intended for 60Hz. This could lead to core saturation, excessive current and excessive heat so a step down transformer may not be an option. I don't know how big a risk this is.
     
  3. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    Miserable schematic. Gonna have to start with the voltage limits on the tubes. Kind of reverse engineer it and then find a 50Hz transformer for it. Hammond is the place to go for transformers in the U.S.

    Try reading the voltage ratings on the bigger capacitors.
    List the tube numbers here.
     
  4. Tommy Sanders

    Thread Starter New Member

    Aug 31, 2016
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    0
    I had no idea that the Hz difference could lead to damaging the amp. So many of my friends use step down transformers in the UK for their american amps without incident.

    thanks for that attachment no.12

    I'll have a look inside the amp and see if i can get more info on the tubes and caps.

    In the meantime I think i'll buy a 100W step down and at least have a play.

    Do you know whether the Hz difference is likely to cause any unwanted noise?
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    The tube numbers are on that pdf - 6X4, 6BQ5, and 12AX7.
     
  6. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    I'm glad you could read them!
    I knew 2 of them but I forgot the last part of the 6BQ number.:(
     
  7. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    The power line won't make noise. The antiquity of the capacitors will.:eek:
     
  8. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,891
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    You might get more mains hum as the supply filtering will be less effective.
     
    #12 likes this.
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