Greetings !

> hi, i just found an old hp345.
> there are several problem with it:
> - no screen (3 BNC connector at the rear)
Should be labeled R, G and B from left to right and carry a colour video
output with sync on green as you may have already guessed

> - no keyboard (the connector doesn't seem realy conventional)
HIL, something HP specific, in most ways better than anything else in
use today ( besides from USB maybe ) but not really common these days.
Should be fairly easy to get. You can chain up to 10 devices ranging
from keyboards, mouses over graphic tablets, dial boxes to speakers and
ID modules ( an attempt to standardize dongles ).

> - no harddrive
Should take almost any older SCSI and SCSI-II drive. Beware of Quantum
and IBM drives since the BootPROM assumes rather rigid timing that most
newer drives don't meet. Curiously enough my ZIP, my 1GB Seagate drive
and most older <500MB drives have no problems.

> - when i switch it on i got this sound 'i o o i i i o'
> 'i' is a high sound
> 'o' is a low sound
Can't say anything about this.

> can i do something with that computer ?
Anything that a UN*X workstation can do :-)
Maybe some low end server since the CPU power isn't exactly comparable
to todays standards. ( a 50MHz MC68030 with 68882 FPU )

> is it working ?
Maybe. take some nullmodem cable and attach some kind of terminal ( any
computer with a decent terminal program will do ), set it to 9600 baud,
7E1, maybe XON/XOFF, don't really know and fire up the hp. it should use
it's RS232 as console when no keyboard is found. Maybe someone else can
tell you more about this since I never really used the serial console
mode.

> (i don't have any manuals)
You should find lots of info on the NetBSD/hp300 pages

> is it possible to access to the firmeware throught the serial port ?
definitely yes, maybe with some obstacles
 
hope that helps a bit
Michael