HP 2113B psu question

One of my HP 2113B CPU's doesn't boot the right way, after switching it on all lights are on except the over flow light which stays out. I know it should be an memory error, but removing all the memory boards and starting with a known good memory controller and memory board gives the same result. Because the PSU has the power fail option and I removed the batteries and placed the plug at the battery in connector, I now suspect the PSU. The voltages checked out ok, except the 5M and 12M voltages come up a few seconds (5 to 10 seconds) later than the rest of the voltages. I'm afraid the time interval is too long but I'm not sure. Is there anyone who knows what the interval should be ? Or has any clou why it's not working ? -Rik