Hi, good news; the SE/30 is working perfect after replacing the SCSI chip.
You were right techknight!
After the NCR 53C80 was removed I checked all traces to the SCSI chip. From UK6, UI8, UK11 and UJ11 to UI12. From UI12 to internal SCSI connector J5. All OK. The earth and +5 V connections also OK . The VIAs under the chip: OK when measuring from top layer to bottom layer on the board. After cleaning I replaced the chip with a AMD 53C80 from a board destroyed by battery leakage.
Its working perfect, I have run it for one hour without problems. Its booting much faster than before. With the old SCSI chip it took about 30 sec from turning on to starting the SCSI disk. Now its 5 sec.
Thanks for all help and advice.
Bengt