18Watt.com

Hello,

I am working on an 1974x clone as I managed to get my hands on a pair of original Dagnall transformers. I am rebuilding/cloning the circuit from the 1974x by looking at pictures of this amplifier and schematics. It's the second amplifier I am building.

Now I started on the OT connections, but the OT is missing data about the wire colors and AFAIK there's no datasheet of it online. (It's the Dagnall D4910).

The following wire colors are on it:

- Brown (screen for V4 by looking at pictures)
- Red (screen for V5 by looking at pictures)
- White (not sure, but I think it's connected to B+ 16uf+32uf cap)

Then I am stuck with the following wire colors and they all seem to go to the output jacks/impedance selector:

- Green
- Yellow
- Black
- Orange

As I don't have my hands around an original 1974x, I am hoping somebody here has one who can take a look where the wires are supposed to go?

I am aware I can measure the transformer ratio's by connecting a low voltage source to the screen wires and measure the voltage from the remaining wires and center tap. I am a bit scared to do so, since I don't even know what wire the center tap is. Hopefully somebody can help me out, thanks!

Measure the resistance of your OT primaries. Two wires connected (for example, red + white), may be the same as 2 other wires connected (for example brown + white), but will be half as much as two other wires connected (for example brown + red). My examples are an assumption based on your assumption, but may not actually reflect the correct pairs.

Whatever combination has the highest resistance are the outer wires of the primary. The 3rd wire is the center tap and goes to B+.

Thanks,
Josh

The secondaries 'might' resemble the Hammond 18W OT. They're the same colors.. maybe they're alike