how do you preheat the bottom of the board?
If you don't want to buy a specialized pre heater, an electric skillet works great. Something that can get up to 400F. Make sure it's not placed directly on it, prop it up on some screws or what ever you deem suitable. It may not be necessary but it has given me nothing but 100% success putting chips on. Good luck bud, and remember the flux.
You want to preheat the board to prevent flexing cracking large temp differences that break things. Warping or breaking your board would probably ruin your day.
thanks
figured it wasnt rocket science. and low tech is my style when possible.
my jally is a very early one with the "hot mosfets" buts its been running fine flashed to 8.2 ghz with a 120v 20 watt muffin fan on it for 6 months now. it doesnt owe me a thing at this point I guess. time to add some heatsinks to the mosfets and push it.