TU81+ spooks (was: Re: first step getting VAX 6000-400 booted ...)

O.K. it would have been too good to be true. I got quite far with my Ultrix, but then I got stuck with being unable to boot from the TU81+ drive. My VMS 5.4 does detect the TU81 just fine, calls it MUB0 and allows me to mount it and write files to it. I think I have now a bootable 9-track reel with at least the first 10 files of the Ultrix 4.1 bootable tape ready to go with all blocksizes as required. It was fun writing! But trying to boot this still brings up the old error: ... XBI D 1+ DWMBA/B (2107) 000A 2+ KLESI-B (0103) 0006 ... Initializing system. ... Loading system software. ?06 Halt instruction executed in kernel mode. PC = 200D7264 SAVPSL = 041F0600 ISP = 0003FBB8 ?3D Error initializing I/O device Bootstrap failed due to previous error. ans this goes all too fast certainly the tape never starts moving before the error. So I tried checking for the TU81's unit number (may be it's MU1 or MU4 or MU213, who knows? First thing is when I power up the TU81 it shows 000 on the front panel, but as soon as it is initialized the display remains blank. So, perhaps it has no unit number set at all? The manual says in order to set the unit number you have to go into TEST program 04. Which I did, TEST - STEP - STEP - STEP - EXECUTE. But then it only says E77 and that's it. This means, something is wrong, but what? The manual only says to call DEC field service. I know the drive works fine, the diagnostic test 01 has passed just fine and VMS works happily with it. So, who knows about the TU81 and how to set a unit number or make it bootable otherwise??? (PS: yes, I had the drive loaded and online when I tried booting, did that offline mistake once before, but not here.) thanks again for your excellent advice, -Gunther