I've been asked to resubmit my question with more detail - so here it
is.....

The video display is only bright and readeable when the modem board in
installed - no phone line connected, just the modem board plugged into an
ISA slot.  When the modem board is removed the display dims to the point
where the room has to be darkened in order to see even see it.  Reinstall
the modem and the display returns, take it out and it goes dim again.
All these plug ins and removals are done with the computer 'off', of
course.

The computer is an IBM compatible, 486DX/33 with 4 MB RAM, dating from
late 1991(Gecco brand, but company now defunct).  The operating system is
DOS 6.22.  Have never had a problem with it and it ran fine long before I
installed the modem, which, by the way, is a US Robotics 14.4 KB
Sportster.  The video card is a Tseng Labs with 1 MB RAM, as I recall.
It does have an on-board BIOS chip.

There are other problems with the computer which may or may not be
related to this problem, eg. the mouse doesn't work even though I've
installed several drivers and tried several different mice (?) mouses
(?).  The IRQ setting, #4, seems OK for COM Port 1.  I will put in a bus
mouse next to see if this solves the mouse problem, but the display
problem is a big mystery - so far.

Suggestions/ideas/thoughts/sympathy, etc.

Lewis Emerson
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