Pacific Output transformer question

[Gibsonman63]

I am getting ready to wire the output transformer to the power tube sockets. I have a green, purple and blue wire. The blue is the center tap. Of the remaining two wires, does it matter which one goes to which socket. I want to make sure to get this correct because I won't have enough wire to swap them later if I run it the way I am planning on.

[Structo]

Leave the wires long, you have a 50/50 chance of getting it right.
If wrong it will howl and let you know.

[Gibsonman63]

Ok, I will run with that for now. Does anyone know why it makes a difference or how to get it right on the first attempt?

I have read so much tube amp stuff the last two years I can't remember what information came from where!!! Swapping the OT leads seems to be a common fix for people building thier own amps from what I have read.

[paulster]

In a nutshell you need to know the phase relationship between the primary and secondary winding of the OT and then use this information in conjunction with the relative phase of the two PI outputs to ensure that you will end up with global negative feedback rather than global positive feedback, i.e. howl.

I always check each OT I get by running a signal into the primary and comparing the primary against the secondary on a scope because then there's no room for error, but if you aren't able to do this then you need to follow an established schematic/layout.

The problem comes when some winders occasionally (and inadvertently) get the colours on the primary coil ends round the wrong way. That's why it's best to leave your leads long at first just in case, unless you've done the testing yourself and are sure of the results you're going to get.

If you follow a known good layout, and ensure that the input to the PI, output from the PI to the power tubes and the transformer wiring are spot on then you've probably got a high 90's percent chance that it'll be fine.

[PlinytheWelder]

FWIW, on my express with a Pacific OT the green wire goes to the power tube farthest from the OT.

[img977]http://verosurfcam.com/TW18.jpg[/img]

The output tubes are rotated 180 degrees on mine, but that doesn't matter with phase.

[Big Jim]

I figured mine out by reading the little notation at the lower left section of Ron Worley's pictoral layout. It explains wire color substitutions for Pacific and vintage Heyboer trannies. Of course this would only be good if they are wound properly.
Jim

[Gibsonman63]

Thanks guys,

I don't have a scope yet, so for now I will leave them both long enough that I don't paint myself into a corner.

[Allynmey]

Remember...purple to power board (closest tube socket to the power board) and you'll be fine with Pacifics...they are very consistant and never had one reversed!