Cornet at 240V

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hagtech

Cornet at 240V
« on: 23 Aug 2003, 08:29 pm »
You can build a Cornet using the Hammond 370BX (instead of 270BX) power transformer for use internationally.  The 370BX has primary taps for 100V, 110V, 120V, 200V, 220V, and 240V operation.

There is one slight issue  :( .  The primary of the 270BX is rated at 115V, and is used at a nominal 120V.  That means the Cornet design was optimized for this extra 4% output voltage.  Or put another way, the 370BX will result in supply voltages 4% too low.

This is easy to fix :lol: by changing R2 from 6.8k to 3.9k (1 watt) and R21 from 2.4 ohms to 2.0 ohms (5 watts).  That's all there is too it.  Happy soldering!

jh :)

hagtech

Octal Cornet at 240V
« Reply #1 on: 25 Aug 2003, 05:57 pm »
If you want to build the "octal" tube modification to the Cornet using the 370BX, then change R2 = 2.4k and R21 = 0.91 ohm.

Wire the transformer primary tap to the closest voltage you get out of the wall.

jh :)

farsch

  • Jr. Member
  • Posts: 10
Re: Cornet at 240V
« Reply #2 on: 20 Sep 2003, 01:21 pm »
Jim I have soldered now the PCB and connected the BX 370 trannie to the
plugs at the PCB.

2 questions on that:

1. does it make a difference which one of the 2 Red, Yellow, green cables I
connect to which of the 2 yellow, red, green plugs at the PCB?

2. I can't find yellow/brwn on the BX 370, do I need Violet of the bx 370?

Best

René

hagtech

Re: Cornet at 240V
« Reply #3 on: 22 Sep 2003, 07:39 pm »
Quote from: farsch
1. does it make a difference which one of the 2 Red, Yellow, green cables I
connect to which of the 2 yellow, red, green plugs at the PCB?

2. I can't find yellow/brwn on the BX 370, do I need Violet of the bx 370


Good questions.  The red wires are interchangeable.  Same with green and yellow.  I forgot about the purple wire.  It is not used in the Cornet.  Just insulate it and tie down.

jh :)