Hello,

>- there are LEDs at the back, especially red ones numbered 0 to=
 7
>(or 1
> to 8 maybe). Are these diag leds ? How should they look ?

from the DECstation 5000 Hardware Operator's Guide:(think this is=
 
true for 5100 also)

o=3Dlight is off 
x=3Dlight is on

oooo oooo
=3D
If the workstation does not turn on,  device or module is not 
connected properly or is broken

If the workstation turns on, all components of the workstation=
 have 
been initialized, and the workstation is ready for use

xxxx xxxx
=3D
Workstation hardware initialization could not begin

ooxx oxxx
=3D
The firmware could not calculate the cache size.

ooxx xxxo
=3D
The firmware could not calibrate the millisecond delay loop.

ooxx xxox
=3D
The firmware could not start the power-up versus reset code.

ooxx oxxo
=3D
Memory bank 0 could not be initialized

ooxx oxox
=3D
The firmware could not initialize the IO ASIC to a known state

ooxx xxxx
=3D
The ROM in the system module or in one of the option modules=
 could 
not be initialized

ooxx xoxx
=3D
The system console programs could not be initialized

oooo ooxo
ooox ooxo
ooxo ooxo
ooxx ooxo
=3D
The system module or one of the option modules could not be 
initialized. The lights on the left show the slot number of the 
module. This table shows slot numbers 0 (off off off off) to 
3 (off off on on)

oooo ooxx
ooox ooxx
ooxo ooxx
ooxx ooxx
=3D
The workstation was initialized, but there is a problem in the=
 system 
module or one of the option modules. the lights on the left show=
 the 
slot number of the module with the problem. this table shows slot=
 
numbers 0 (off off off off) to 3 (off off on on).

oooo ooox
ooox ooox
ooxo ooox
ooxx ooox
=3D
The workstation software could not be loaded. the lights on the=
 left 
show the slot number of the module where the software is stored.=
 this 
table shows slot numbers 0 (off off off off) to 3 (off off on=
 on).

I hope this helps.

Sincerely,

Daniel Meinhold