IDing leads on old power transformer?

[JJGross]

I have a salvaged transformer that I have no idea which leads are primaries or secondaries. It's from an old radio that was powering a 6V6gt, several 6S*7 tubes and a 5Y3gt rectifier. I'd like to use the transformer to build a Champ clone since it looks like this thing already has practically everything I need.

How do you figure out which wires go to heaters, rectifier, etc in an old transformer that has no markings on it? I'd prefer to not just guess which 2 wires I should hook up to mains.

I should also mention that there are 10 wires coming from it and the colors are pretty faded (built in 1947) and they're 3 green solid core, 2 black stranded and the rest are what look like 2 sort of white solid core (very dirty) and 3 'other' stranded (maybe red 40 years ago).

Thanks in advance.

[stokes]

I would assume the black wires to be the primary.I have a pair of alligator clips connected to a 2-prong ac cord,with a 1 amp fuse in line.I plug this into a current limiter,connected to the black leads and then measure the voltage at the assumed secondary leads.It is safe to assume the red would be HV,green to be 6.3v,and yellow to be 5v.From what you describe I would say the 3 red are your HV,with one being a CT,if you check the voltage between each it will be obvious which is the CT.Same with the 3 green,two being the 6.3 and one being a CT.The two "sort of white" could be yellow?They would be the 5v for your rectifier.No CT on the 5v.

[Enzo]

And if you can pop the bell cover off the transformer, a lot of times the wire insulation color is still easily visible inside.

[bob p]

And if you can pop the bell cover off the transformer, a lot of times the wire insulation color is still easily visible inside.

oh, good point. i came across some old Thordarson PTs that were so filthy that I had no idea which leads were which, and popping off the endbells took care of the problem.

[JJGross]

Thanks for the help guys. Now I have a place to start.

Cheers,
- JJ