pyrography power supply questions OT

Am trying to hack together a set up to power a wood burning pen.
The set up is similar to a hot wire power supply. Just a light dimmer
switch and a transformer.
After a little playing I managed to get it to put
out the right amount of power to heat the pen tip to red hot
and able to burn wood, leather...
The problem I now have is that after a few minutes the transformer
starts to heat up and I get that lovely "electrical stuff burning"
smell.
I am about to give up and just buy the right supply, but before I do,
just wondering if there is anything obvious I am missing.
Some of the details:
The dimmer needed a little adjustment to get the output from the
transformer down to about 4-6 volts. I've replaced the 150K trim pot
with a 330K resistor.
The transformer was originally set to put out bout 24V ac. and I've
taken 15 turns off the output winding. Output voltage at full power
is down to 19.5
I can lower this to less than 1 volt using the dimmer.
The winding resistance is about .3 ohms and that is the
approximate value of the burning tip resistance.
Before I started hacking the transformer, it had a 4 amp breaker
built in. So I assume that it was able to handle about 96 W
I assume that the transformer must dissipate the same about
of heat as the burning tip and this should be in the 100 W
range.
That doesn't seem to be too much but...
Appreciate any help, ideas...
DOC