Error 63493 dc bus or motor cable short circuit

[safacond]

Hello Guys, I have a C3G-900 entering DRIVE ON, 500ms after crashes 63493 on the third axis. I checked all the cables and motors and they are perfect. Windings find a resistance of about 3 ohms for large motors and about 6 ohms to others. Among other things, if I exchange links with the second of the third motor, the same alarm is on the fourth axle!  In any case, both drives are in faul system (red LED).
 Reading the causes and remedies, thus excluding the problem of the motors, could also be a problem of DC bus or recovery circuit. I measured the voltage is 320V. I also measured the resistance of the recovery resistor which is 9 ohms.
 It all seems OK! It 'may have spoiled both drives at once?
 Prior to this failure I replaced the card from an SCC 10120361 rev.1 with firmware 2.31 to 10120361 rev.2 with firmware 2.41, do you think could be the cause? 

[safacond]

Hi guys, in the meantime I did some tests and found that the problem was both servo amplifier unit (SAU). I replaced them both and now it works.