In case your battery draw too much current. If your new power supply, new power cable, new MB are good, after you remove battery, I can't image what else prevent you from power on unless you damage other parts during your experiment.
If you are in SF bay area, I can help you.
Another option is buy a smae type NB on ebay, some broken LCD NB are very cheap. I fixed my NB by bought a new MB at $137, later I bought a broken NB at $53, combined with my broken MB I have my second NB with some defect(Not charging battery).
For your first returned MB, did seller say anything about their MB is good or bad? Did you buy the 2nd from same vendor? at what price?
