Wiring for EA2503 Output Transformer in Hairball Silver

[Troisi]

Hi all,

I'm at a stopgap in building a Hairball Silver 500 mic pre. I've finished the input stage, zobel, and power sections, but I am at a loss on how to wire a Ed Anderson EA2503 to the Elements (silver) PCB.

I was communicating with Mike Mabie who was very helpful, but eventually we both got stuck.

I am here to ask the community for help to finish this part of the build.

Mike gave me a 2503 schematic, then later one with handwriting on it indicating the HI and LO Primaries.

The EA2503 has 8 colored wires like the original, but only four will be attached to the PCB.

What I need to know is what to do with the remaining four wires. The connections to the PCB pads are as follows:

1. Primary HI - RED
2. Primary LO - BROWN
3. Secondary HI - BLUE
4. Secondary LO - ORANGE

This leaves green, yellow, violet and grey.

Are any of the below possible solutions?

1. Solder together grey(7) and violet(8), cut short and tape to avoid short, and also do the same with green(3) and yellow(5)
2. Solder all four (grey violet green yellow) together and cut and tape
3. ??? (suggestions?)

Mike also suggest possibly connecting grey(7) & violet (8) with a relatively high ohm resistor, which would mimic some resistance of the circuit of a meter.

I'm basing most of this thinking from handwriting on a schematic that indicates four terminations of the output on the 2503. This is attached.

Any help is very very much appreciated.

Thanks

 

[Walrus]

If the EA2503 uses the same colours as the API 2503, then if your using Blue and Orange as the output, you must join together the Yellow and Green to complete the circuit or you will not have any signal out.
The Violet and Grey must be left unconnected, do NOT join them together as that will constitute a short on the transformer.

 

[Troisi]

If the EA2503 uses the same colours as the API 2503, then if your using Blue and Orange as the output, you must join together the Yellow and Green to complete the circuit or you will not have any signal out.
The Violet and Grey must be left unconnected, do NOT join them together as that will constitute a short on the transformer.

Aha.

That was going to be #3 on my list of possibilities, but I didn't get that far. This makes sense.

I will look for evidence the colors match between EA and API design of the 2503. Assuming they do, I will solder together Yellow/Green, tape off to avoid short, then cut violet, tape, as well as grey, tape, individually.

By "unconnected", the Violet and Grey will just float inside the case with electrical tape on the ends to avoid shorting on anything, I assume.

Thank you for taking the time to respond. Very much appreciated.

 

[Troisi]

Just to add, in case anyone else finds this post useful, the Ed Anderson EA2503 Output Transformer has the same lead colors as the vintage API 2503.

It says this in the bottom left side of the datasheet.

 

[Walrus]

By "unconnected", the Violet and Grey will just float inside the case with electrical tape on the ends to avoid shorting on anything, I assume.

Correct.

 

[Troisi]

Correct.

Wonderful.

Thanks so much for your help!