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s2 Amplification > Forums > Technical Support > Output transformer wiring: Hammond 125CSE
 
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SDPaul
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Registered: 09/02/06
Posts: 2

    09/02/06 at 04:33 PM
  Reply with quote#1
I have the Epiphone VJ upgrade kit which included the Hammond output transformer. I am confused as how to wire this thing up, or more precisely, how to equate the secondary side wires to the impedance (4, 8 16 OHM) that I want to have in my speaker outputs. According to Hammond, the white secondary wire, for example, can either be 32, 16, or 8 OHMs, depending upon the impedance in the PRIMARY side of the transformer. The same pattern exists for the other secondary wires.

This is vastly different than the stock tranny, which simply said to use the red wire for 8 OHMs, etc.

I guess I don't fundamentally understand what is happening at the primary side of this Hammond transformer. The resistance of the primary side would seem to be a function of the transformer itself, and I would expect that to have been supplied by the manufacturer. To know the impedance of the primary side, I think I would have to know both the transformer's innate resistance and also what the amp is trying to push through it, but I'm really in over my head in these waters.

If anybody can offer some assistance, it would be greatly appreciated.
s2
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    09/04/06 at 08:33 AM
  Reply with quote#2

The secondary is a function of the primary.  A transformer is simply an impedance matcher, so one side depends on the other.  I recommend a 5K primary for a VJ, so that makes green 4 Ohms, yellow 8 Ohms, and white 16 Ohms.  You don't use the orange wire in this application.


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SDPaul
Apprentice
Registered: 09/02/06
Posts: 2

    09/04/06 at 10:43 AM
  Reply with quote#3
That seems simple enough!

Thanks very much for your quick reply, s2! I'll let you know how it sounds, when I gotten this project completed!

Just in the spirit of further enlightenment, what determines that the primary is set at 5K OHMs?

eagleeye
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Registered: 11/16/08
Posts: 3

    11/16/08 at 01:34 PM
  Reply with quote#4
Would this be the same wiring instructions for the Hammond 125-ese. Or is there another way for the 125-ese? Thank you, Dave
s2
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    11/17/08 at 07:47 AM
  Reply with quote#5

The wiring is the same for all of them.


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eagleeye
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Registered: 11/16/08
Posts: 3

    11/26/08 at 01:25 PM
  Reply with quote#6
Would anyone know if I can replace the R12 resistor with a 10k ohm? Or can I use a 4.7k 5 watt resistor without trouble? I burned up the original yesterday from putting the tubes in wrong. I know pretty STUPID! Any advice would be appreciated! Or can I use a 2.2k 3 watt for R12 and R13?
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