New 5F1 Build question

I am building a 5f1 and have an output transformer from a 65 Princeton Reverb ReIssue that I would like to use. Is this possible? There are 3 wires on the primary side a red, brown and blue. I figure the red goes to the rectifier pin 8, and the blue goes to the 6v6 pin 3. What is the brown for? I have attached a schematic of the Princeton if that will help. Or here is a link to the PRRI schematic.

http://support.fender.com/schematics/guitar_amplifiers/65_Princeton_Reverb_schematic.pdf

Princton Reverb is a push/pull amp. 5F1 is a Single Ended design....You should use a OT built for a Single Ended amp. They not expensive... You can get them for as little as $25.

Thanks for the info. I have one already I was going to use for another project .