Re: Safely swap monitors?
- From: "jakdedert" <jdedert@xxxxxxxxxxxxx>
- Date: Sat, 9 Jul 2005 15:43:38 -0500
"Choreboy" <choreboyREMOVE@xxxxxxxxxxxx> wrote in message
news:42D02F4A.8B1E3E31@xxxxxxxxxxxxxxx
>
>
> jakdedert wrote:
> >
> > "James Sweet" <jamessweet@xxxxxxxxxxx> wrote in message
> > news:DXnze.5161$VN3.1101@xxxxxxxxxxx
> > >
> > > >
> > > > Why is a monitor less likely to damage a computer? If the monitor
> > > > proves bad, as indicated by the open on a pin that should be
grounded,
> > > > won't I still have to connect a good monitor to the neighbors'
computer?
> > > >
> > >
> > > It's not, it's more likely as it contains much higher voltages right
on
> > the
> > > same logic board as the low voltage stuff, but the chance of damage is
so
> > > remote it's hardly worth mentioning, you're more likely to damage one
or
> > the
> > > other by dropping them.
> > >
> > > > What might be wrong with a computer's video card that would damage a
> > > > monitor? I could check the video outputs with a scope. Would that
> > > > assure me that it was safe to plug in my monitor?
> > > >
> > >
> > > Nothing, not on a reasonably modern monitor anyway. Some of the early
ones
> > > would fry if fed an invalid sync signal, anything made in the last
decade
> > at
> > > least will just shut down.
> > >
> > > > I thought I'd connect a good monitor and see if the computer worked.
> > > > What's the point of disconnecting everything in the computer without
> > > > first knowing that anything is wrong?
> > >
> > > There isn't one, though if it doesn't boot you should disconnect
anything
> > > non essential and see if that allows it to boot.
> > >
> > My point. There's already evidently more things wrong than just video,
as
> > evidenced by the OP's description of the audio. At the very least, pull
> > that sound card which is squealing (unless it's integrated into the
> > motherboard).
> >
> > Lightning's a funny thing. I had a system which got hit. The only
thing
> > that went out was the onboard IDE/floppy controller...in the days when
> > onboard controllers were rare (Pentium 60). Disabling it in BIOS
allowed
> > the system to live out it's life in harmony; with the addition of
controller
> > card.
> >
> > I never fully trusted the machine, however, and thereafter relegated it
to
> > non-essential duties.
> >
> > I had another machine which fried in the same incident. About all that
I
> > could salvage from that one was the hard drive and case/ps. It even
blew
> > the fairly espensive speakers which were connected, as well as the
parallel
> > port in the printer.
> >
> > My son brought a machine back to me, one which I had originally built
from
> > all new components, as a graduation present. That one was totally
> > unsalvagable. I mean that *nothing* was usable except the case. The ps
> > blew, all the memory, motherboard, CPU, hard drive, all outboard cards
> > (sound, video, modem etc)...a complete loss.
> >
> > Lat week's strike (detailed in this forum) only took out one of the many
> > computer-related devices in the household (laser
> > printer/fax/copier/scanner); while destroying or disabling many, many
pieces
> > of telephone and home entertainment devices.
> >
> > If the OP can get it to boot by simply replacing the monitor, fine. If
not;
> > what I said.....
> >
> > jak
> > >
>
> Taking the gist of your advice that a monitor *could* damage a computer
> and visa versa, I checked resistance with DMM on the monitor cable and
> found an open on the ground for the green signal. So there is something
> wrong with the monitor, although it seems possible that it was working
> with the green shield grounded only at the computer end.
>
> The next step would have been to check the connector live with a scope,
> but I would have needed a half-inch of tubing to keep my probe on each
> pin.
>
> The computer output was easier for a probe, being holes. None of the 15
> holes carried any signal I saw. Two sat at 5V. The rest were at
> ground. With a DMM, one of the signal holes (horizontal sync, I think)
> showed zero ohms, but that could be normal.
>
> Satisfied that nothing looked dangerous to my monitor, I hooked it up
> and, as expected, got only the amber standby light.
>
> I imagine a problem elsewhere could put the video card to sleep. Does a
> video card sleep with two outputs at 5V? If not, the card must be
damaged.
>
> I don't want to try their monitor on my computer until I scope the
> monitor pins for anything that looks threatening. If their monitor
> works and it's normal for two conductors on a PC video output to sit at
> 5 Volts, I suppose the next thing is to see if their computer will run
> with everything possible unplugged, as you recommended.
Exactly why I just 'shotgun' them whenever I suspect lightning problems.
'Something' is damaged...often many things. It's a lot quicker (of course,
I have monitors, RAM, video cards etc, spilling out of every corner) to just
see what 'does' work as opposed to trying to track down 'the' problem with a
lot of diagnostics. It takes five minutes to pull everything out. It takes
another minute to see if it will boot in that configuration, and if it
won't, there's not much use in going any further unless one has the
necessary spares to replace MB/CPU. If the computer's more than a couple of
years old, it's cheaper to replace; unless you're doing it as an
'excercise'.....
In your case, it would be simple to google 'VGA pinout' in order to see what
signals should be on each pin, if you want to diagnose at that level.
jak
.
- References:
- Safely swap monitors?
- From: Choreboy
- Re: Safely swap monitors?
- From: jakdedert
- Re: Safely swap monitors?
- From: Choreboy
- Re: Safely swap monitors?
- From: James Sweet
- Re: Safely swap monitors?
- From: jakdedert
- Re: Safely swap monitors?
- From: Choreboy
- Safely swap monitors?
- Prev by Date: Re: Orion TV STV2763 "Dead"
- Next by Date: Re: Lightning protection
- Previous by thread: Re: Safely swap monitors?
- Next by thread: Re: Safely swap monitors?
- Index(es):
Relevant Pages
|
