Custom Toroids - what is a man to do?

uglymusicuglymusic
in DIY
This discussion was created from comments split from: The SECA Boards.

Comments

  • sovereignsovereign
    edited October 2016
    I have these custom made toroids that I was going to use for another project which I have now ditched.  They are currently custom made 350Va on a 500Va iron.  and the secondaries are 15-0-15v.  For the new 40W SECA they need to be 22-0-22.  So I am sending them off today to be adjusted.  However whilst they are being re wound I have asked for them to be changed to 500Va - Bonkers I know but I have always had a thing for big toroids, as if these aren't already big enough.


    However, the toroids would need to completely rewound and use a higher flux density  - so they would no longer be audio grade if I wanted 500VA,  I can get them to around 425VA and they will still be audio grade (but not as good as the 350Va TM897A I have now), and the need to completely rewind them as thicker primary wire will be required.

    Not entirely sure what to do, Im sure Colin will just slap me on my bald spot and tell me to leave the rating at 350Va and the fact that they are custom made using excellent quality materials rather than what you can pick up off the shelf, and they are on a 5Va iron , I should leave as they are and just have the secondary voltage increased to the 22v needed.
     image
  • DocfosterDocfoster
    You're rambling, man!
  • sovereignsovereign
    I had to watch your / tutorial video in order to remember how to post pictures here.  I must be getting  old  :-O
  • quickiequickie
    Probably easier to just sell them, and buy some new ones ?

    Nothing wrong with custom transformers, but I really can't see the point, unless you need input/output voltages that you can't get off the shelf.

    I really must sort out what I have here. Got dozens of the bloody things !


  • quickiequickie
    edited October 2016
    If you must have custom, then don't discount Toroidy.

    Last time I bought some, they were nearly 50% cheaper then CW and just as good imo.

    Spec a 240v primary, as should run quieter then 230v.
  • cj66cj66
    Docfoster said:
    You're rambling, man!


    BTW, a second vote for Toroidy.
  • DocfosterDocfoster
    cj66 said:
    Docfoster said:
    You're rambling, man!


    Sounds right up James' street...
  • DocfosterDocfoster
    quickie said:
    Spec a 240v primary, as should run quieter then 230v.
    That's interesting.
  • AntiCrapAntiCrap
    No not always it depends on construction and it there is any noise or flat topping on the input current/volts.
    Noise can be mechanical i.e. poor wound core or electrical/mech, vibration due to slack windings, or saturation caused by to many A/T or saturation due to in put flat topping causing saturation at peak current only or even all of the above.

    I did lots of testing to find the cause of transformer noise when I worked under contract with Naim at the same time I offered a cable design which as you are now aware they turned down, shame it could have been a good cable. 
  • uglymusicuglymusic
    Are you winding him up, Col? (I'll get me coat!)
  • DocfosterDocfoster

    quickie said:
    Spec a 240v primary, as should run quieter then 230v.

    AntiCrap said:
    Noise can be mechanical i.e. poor wound core or electrical/mech, vibration due to slack windings, or saturation caused by to many A/T or saturation due to in put flat topping causing saturation at peak current only or even all of the above.
    So multple possible causes. Including lower rated primaries.
    I do know DC can have some effect, as sticking in a DC blocker killed dead toroid hum in my balanced PSU (the one Sov made) and the somewhat smaller toroid in my bass amp.
  • sovereignsovereign
    Interesting thoughts chaps. I think I'll leave as they are and just add extra windings to go from 15-22v on the secondaries
    AntiCrap said:
    No not always it depends on construction and it there is any noise or flat topping on the input current/volts.
    Noise can be mechanical i.e. poor wound core or electrical/mech, vibration due to slack windings, or saturation caused by to many A/T or saturation due to in put flat topping causing saturation at peak current only or even all of the above.

    I did lots of testing to find the cause of transformer noise when I worked under contract with Naim at the same time I offered a cable design which as you are now aware they turned down, shame it could have been a good cable. 
    True, true.  But these toroids are customs made using extremely high quality materials.  The chap who makes my toroids also makes some toroids for airlink when they want custom toroids made.  He has to make them to Airlinks requirements, and apparently their requirements are pretty shabby.  
  • sovereignsovereign
    Did Dave get his coat and leave the building?
  • AntiCrapAntiCrap
    Now on no load test the winding voltage on the secondary, do it with great care, we do not want large bangs and dead chews.
    Then turn it OFF after making a note of the voltage.

    Then put one turn of open ended wire insulated thru the toridal and switch ON and make sure the end are not shorted now measure the volts AC on this single turn.
    Make a note of it OK next.

    Now we have to do some sums OK deep breath.

    The open circuit winding let say is 15V AC the single turn is 1V A we need 20V so we are 20 - 15 = 5V missing OK 1 turn lets us have 1V so 5V divided by 1T = 5 turns.

    OK now put 5 turns around and thru  the toridal with the power OFF
    Insure no shorts and power up the transformer 
    Measure the now 5 turns and we see that it should be 5v AC OK if not change the turns up or down a turn at a time.

    Now the tricky bit yes power OFF first

    Now take one end of your secondary wire and join it to one end of your 5 turns and power up , measure the volts across the transformer secondary and the new 5 turns.
    If you get 20v AC the great if not and you read 10v AC then reverse the winding connection and use the other end.

    You have now just check the phase.
    Now just keep doing this again for the second voltage out.

    Now completed wind the new winding neatly and insulate from fingers and there you go, 

    OK you will have reduced your output power by a small amount but saved yourself money.
  • sovereignsovereign
    Thanks for the insight Colin.
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