Have you taken the board out and cleaned it yet? Make sure to inspect all the chips, and look for bent over touching legs.

So far i've had a no chime/boot issue macintosh LC-II someone bent one of the cpu legs over, it was touching the other one. This was a result of the buyer not being careful when removing the NIC card before the sale.

Also, I had a no chime/boot boot issue with my LC-III, where a tiny little speck of solder fell bridging just 2 of the legs on the main VLSI chip, I found the solder speck and removed it with my dental pick, hit the power switch and it was booting just like it used to.

Has anyone ever had to re-cap a Quadra 700?