Although mono displays and even dual displays have existed from day one, a
mono card is being a non maintained thing. This cards have a 6845 chip, or
equivalent, which has to be programmed by the bios to work. So could happen
that your bios does not have this code (I have seen this happening). If this
is the case, I even think an upgrade would be difficult.
You can try dual display (mono and VGA and two monitors), testing from color
with DOS "mode mono" if you switch; if not, test memory at B0000-B7FFF with
read-writes. If memory is OK, then the card may be good but no code in
mobo's bios. You can try to look if the bios includes code for the 6845 as
mono. Also, check if the printer port (3BC+) works.
Old cards had a switch color/mono for choosing the primary display when dual
display, but this has been substituted in modern bios by programming which
should be the primary display in bios. This has nothing to do with your
problem.
BTW, I'm writing this from a dual display (color/mono) PC recently upgraded
to W98. If I open a DOS session, switch to the mono, and there I run a DOS
text program using the mouse (such as Edit) the mouse works on the mono, but
the cursor is not seen. This is a bug on W95 from day one, very easy to
solve (when the mouse crosses to the inside of the window belonging to the
DOS session, if it has the focus, and we are in mono, then show the mouse
cursor as a square on the mono), but nobody seems to have told the
programmer in three years how to solve it, and the bug remains in W98. So
you see this things have no maintenance.
************************************
Javier Vizcaino. Ability Electronics. [log in to unmask]
  Starting point:        (-1)^(-1) = -1
  Applying logarithms: (-1)*ln(-1) = ln(-1)
  Since ln(-1) <> 0, dividing:  -1 = 1     (ln(-1) is complex, but exists)
-----Mensaje original-----
De: [log in to unmask] <[log in to unmask]>


>Well, this new board works ok, with a VGA adaptor.  But a hercules adapter
>gives only a blinking cursor at the upper left corner of the screen.  No
>text is displayed.
>
>This card works ok on the 386 motherboard, but nothing (except the cursor)
>with the newer board.
>
>May I (again) request clue?
>
>Alan Davis