Originally burned several resistors beyond repair on an Onyx VGA upgraded with 667 Mhz. Replaced with a used 550 Mhz logic board from reputable dealer, upon startup received 3 beep RAM failure. I swapped memory sticks with two brand new, still 3-beep RAM failure. Attempted second logic board swap with a second 667 Mhz board I purchased, still 3-beep RAM failure, all combinations of RAM sticks in all positions--I've read most posts on the subject. I do get one beep with no sticks. These boards were certified tested, two bad apples seems indicative of a deeper problem, any suggestions?