1. Time for some upgrades in server hardware and software to enhance security and take AK to the next level. Please contribute what you can to sales@audiokarma.org at PayPal.com - Thanks from the AK Team
    Dismiss Notice

inproving safety in old hot chassis (1947)

Discussion in 'Tube Audio' started by elnaldo, Nov 10, 2018.

  1. elnaldo

    elnaldo Addicted Member

    Messages:
    7,354
    Location:
    Buenos Aires GMT-3
    Hello. Restoring this old COLLARO MICROGRAM, I see the output transformer (and speaker) is connected to mains. Parts are supposed to be "non accesible", but I'd like to know if I could improve safety in this case, if there is a way to isolate the output transformer from mains, perhaps with a properly sized safety capacitor. Actually I don't know the purpose of this connection. I'd prefer a floating output transformer if possible.

    Schematic attached:
    Collaro Microgram Circuit-V2.jpg
     

     

    Please register to disable this ad.

  2. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    36,797
    Location:
    Southern NJ
    It needs to be connected to ground to complete the negative feedback loop. You'd need a fair size capacitor to make this work, large enough that it may as well be directly connected to chassis like it already is. You could replace the power transformer with a real one instead of the autoformer that it currently uses though. That would give you mains isolation.
     
  3. arts

    arts Super Member

    Messages:
    3,739
    Location:
    Qc, Canada
    Yikes,a 220V hot chassis:yikes:

    Isolation transformer,no question.
     

Share This Page