Determining current capacity of a htr winding

[studioit]

How do you go about determining the current capacity of a 6.3v winding in a
transformer if it's not known.It's a pwr trans from an old superscope tape deck and everything else is fine for my purposes except that there are 3 6.3v windings. 1 center tapped and 2 not. The tape deck used a 5v4 rectifier and had 3 6aq5's, 2 12az7's,and 2 6au6's so I Know the 5v and B+ windings have enough capacity.
What I don't know is how they wired the htr circuit, ie if it was divided between the 3 seperate windings. Ideally, for my project I'd like to just use the center tapped winding if it has enough capacity for my project. 5e3 style amp -2 12 ax and 2 6v6.
So is there a simple way to determine the capacity of that winding?

Thanks
Ian talcroft
studio IT

[stokes]

Just wire it up and install the tubes.Check the voltages on the heater and if you get 6.3v with the tubes installed,you are okay.If the volts drop below6.3 you are stressing the winding,in which case you could use one of the other windings to supply the power tubes heaters seperately.

[studioit]

Thanks, But if I do need to use 1 of the other windings what should I do about ground ref? 100 ohm resistors on that tap?

[stokes]

Just put one 100ohm from each leg of the heater to ground,or for a little more hum reduction instead of ground,connect them to the cathode of your power tubes,assuming it will be cathode biased.I always disregard the actual CT and use the 100ohm to cathode.