Looks like I spoke too soon. The dreaded RL8A failure has returned! I made a new OS/8 RL02 pack on vtserver (took the expected three hours at 9600 baud console speed). Booted up the 8/A, so far so good. But then Drive 0 faulted and OS/8 crashed... restarted and it crashed a few seconds later again. I flexed the middle of the RL8A upwards and the system worked. For a while. Then it crashed and wouldn't reboot. Back to where I was earlier in the week - won't even allow SerialDisk to boot if the RL8A is in the backplane. OS/8 on the SerialDisk virtual RK05 works flawlessly if the card is removed. Obviously there is still an intermittent which has come back. Maybe there's a tiny thread of something conductive stuck under one of the IC's and I managed to temporarily clear it as I described. Anyhow I am resuming my search for a good RL8A. I have wasted enough man-hours on this flaky board. thanks Charles