First call Mitsubishi (if that is the brand in your QT8) to get pricing on replacement and/or repair. With that pricing in hand scan eBay for the model you need keeping in mind what you find may be used (sometimes new you never know) then check out repair pricing from a reputable servo repair outfit. I highly recommend these guys: Servo Motor Repair - Kollmorgen, Yaskawa, Siemens, Fanuc and more!
I work with Servotech all the time, they are a first rate operation. They may not be the cheapest but their process and quality is exceptional. Do not be fooled by folks that say they can repair for less, I've seen the work of some pretty shody outfits.
Last edited by Pipes; 06-20-2010 at 03:39 AM.