Hey Mark, good to see you...
The control may be toast. I've got a spare lying around that I can ship you if you need one.
This horsepower problem plagued me for ages until I broke down and got the "real McCoy"
Buy one of the surplus treadmill motors and an industrial speed control. Here's where I got mine, and a pic:
http://www.surpluscenter.com 2 HP 130 VDC 3210 RPM MOTOR
Item# 10-1906 $79.95 (you can get cheaper on eBay if you shop)
http://www.mcmaster.com 7793K12 Speed control 10A max (with heatsink)
I'm using the old headstock casting that has no gearing - on yours you'll probably want to pull the weird timing pulley that they use and slap on a regular XL series.
Couldn't tell you the speeds and feeds off the top, but I'm not at all disappointed with the power for shooting steel - I run out of insert before I run out of power since I'm not using flood coolant anymore. I'm doing mostly 3/4" and under bar work in 1018 and 304/303.