Follow the instructions in this link: http://www.geofex.com/ampdbug/pwrtrans.htm
It is possible that the PT is blown but it’s also possible that it’s something else in the power supply, a bad tube can cause damage to other components. When a fuse blows, it’s not because the fuse went bad, use the light bulb current limiter you built when you constructed the TwoStroke (you did build a current limiter, right?) while testing the amp to ensure that there are no dead shorts that could cause addition damage.