Neighbors have a computer that won't work after a lightning strike.
With the video cable connected, the monitor stays black and in the
standby mode. There are howls from the speakers, like feedback. With
the cable disconnected, the monitor will briefly show a notice that it's
not connected. There are no howls from the speakers although the mic
cable remains connected.

With the power off, I checked the pins of the monitor cable to see that
the grounding pins were grounded and the signal pins were not. One
grounding pin is open, so it seems certain that the monitor is damaged.

The next step would be to try another monitor to see if there's other
damage to the system. In case the computer's video card is damaged, can
a monitor be damaged by plugging in to it?

"Choreboy" wrote in message
...
Neighbors have a computer that won't work after a lightning strike.
With the video cable connected, the monitor stays black and in the
standby mode. There are howls from the speakers, like feedback. With
the cable disconnected, the monitor will briefly show a notice that it's
not connected. There are no howls from the speakers although the mic
cable remains connected.

With the power off, I checked the pins of the monitor cable to see that
the grounding pins were grounded and the signal pins were not. One
grounding pin is open, so it seems certain that the monitor is damaged.

The next step would be to try another monitor to see if there's other
damage to the system. In case the computer's video card is damaged, can
a monitor be damaged by plugging in to it?

'Probably' not, but why not try plugging their monitor into your computer?
That's extremely unlikely to cause any damage. Then, I'd take *everything*
out of the neighbor's computer, except the vid card...unplug memory, all
drives including floppy...just leave in the CPU and vid card.

See if it boots up and asks for memory. If so, install that. Keep
going--adding one device at a time--until you find a problem device...skip
that one on the next go-round, until you've ID'd any and all such.

Rinse, lather, repeat.....

jak

"jakdedert" wrote in message
news

"Choreboy" wrote in message
...
Neighbors have a computer that won't work after a lightning strike.
With the video cable connected, the monitor stays black and in the
standby mode. There are howls from the speakers, like feedback. With
the cable disconnected, the monitor will briefly show a notice that it's
not connected. There are no howls from the speakers although the mic
cable remains connected.

With the power off, I checked the pins of the monitor cable to see that
the grounding pins were grounded and the signal pins were not. One
grounding pin is open, so it seems certain that the monitor is damaged.

The next step would be to try another monitor to see if there's other
damage to the system. In case the computer's video card is damaged, can
a monitor be damaged by plugging in to it?

'Probably' not, but why not try plugging their monitor into your computer?
That's extremely unlikely to cause any damage. Then, I'd take
*everything*
out of the neighbor's computer, except the vid card...unplug memory, all
drives including floppy...just leave in the CPU and vid card.



Actually I'd be more concerned about that causing damage than the other way
around, but realistically either way should be fine.

jakdedert wrote:

"Choreboy" wrote in message
...
Neighbors have a computer that won't work after a lightning strike.
With the video cable connected, the monitor stays black and in the
standby mode. There are howls from the speakers, like feedback. With
the cable disconnected, the monitor will briefly show a notice that it's
not connected. There are no howls from the speakers although the mic
cable remains connected.

With the power off, I checked the pins of the monitor cable to see that
the grounding pins were grounded and the signal pins were not. One
grounding pin is open, so it seems certain that the monitor is damaged.

The next step would be to try another monitor to see if there's other
damage to the system. In case the computer's video card is damaged, can
a monitor be damaged by plugging in to it?

'Probably' not, but why not try plugging their monitor into your computer?
That's extremely unlikely to cause any damage. Then, I'd take *everything*
out of the neighbor's computer, except the vid card...unplug memory, all
drives including floppy...just leave in the CPU and vid card.

See if it boots up and asks for memory. If so, install that. Keep
going--adding one device at a time--until you find a problem device...skip
that one on the next go-round, until you've ID'd any and all such.

Rinse, lather, repeat.....

jak

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?

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?

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?

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.

"James Sweet" wrote in message
newsXnze.5161$VN3.1101@trnddc01...


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

jakdedert wrote:

"James Sweet" wrote in message
newsXnze.5161$VN3.1101@trnddc01...


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.

"Choreboy" wrote in message
...


jakdedert wrote:

"James Sweet" wrote in message
newsXnze.5161$VN3.1101@trnddc01...


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

Choreboy wrote:
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.

That's not normal, there should be at least 75 ohms to ground.

---
Met vriendelijke groet,

Maarten Bakker.

wrote in message
l...
Choreboy wrote:
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.

That's not normal, there should be at least 75 ohms to ground.



Which may be what 75 ohms looks like depending on the range the meter is set
on. I suspect there's visible damage inside the monitor, I'd open it up and
look at the board where the cable plugs in. Lightning is interesting stuff,
we don't get much of it out here though.

It won't ask for memory. You have to have memory in the pc for it to do
anything but beep. That's all you'll get without memory BEEEP BEEEP
BEEEP.... If you take everything out except the processor it should
beep..(including memory and vid card) Beeping a good sign and and means the
bios is working.

- Mike

"James Sweet" wrote in message
news:Zmlze.14689$Yb4.6535@trnddc08...

"jakdedert" wrote in message
news

"Choreboy" wrote in message
...
Neighbors have a computer that won't work after a lightning strike.
With the video cable connected, the monitor stays black and in the
standby mode. There are howls from the speakers, like feedback. With
the cable disconnected, the monitor will briefly show a notice that
it's
not connected. There are no howls from the speakers although the mic
cable remains connected.

With the power off, I checked the pins of the monitor cable to see that
the grounding pins were grounded and the signal pins were not. One
grounding pin is open, so it seems certain that the monitor is damaged.

The next step would be to try another monitor to see if there's other
damage to the system. In case the computer's video card is damaged,
can
a monitor be damaged by plugging in to it?

'Probably' not, but why not try plugging their monitor into your
computer?
That's extremely unlikely to cause any damage. Then, I'd take
*everything*
out of the neighbor's computer, except the vid card...unplug memory, all
drives including floppy...just leave in the CPU and vid card.



Actually I'd be more concerned about that causing damage than the other
way
around, but realistically either way should be fine.

James Sweet wrote:

wrote in message
l...
Choreboy wrote:
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.

That's not normal, there should be at least 75 ohms to ground.


Which may be what 75 ohms looks like depending on the range the meter is set
on. I suspect there's visible damage inside the monitor, I'd open it up and
look at the board where the cable plugs in. Lightning is interesting stuff,
we don't get much of it out here though.

I got 75 on the R, G, and B signal pins. Without a schematic, I
wondered if the sync pin was fed by a transformer, in which case zero
ohms could have been correct.

When I checked the monitor pins, a scope showed several problems. A
local drugstore chain has refurbished computers and monitors similar to
theirs for $250. Why fix it?

My own computer is a Mac. I think with a Mac, the display comes up
before it checks the memory. On a PC, would bad memory keep the monitor
light from turning green?

On the PC, a Compaq Presario 1710 I think, all ports except the modem
are on the motherboard. Would I need the hard drive to get the monitor
to light up?

Offhand, I remember I could unplug the floppy drive and the CD drive.

Could corrupted BIOS prevent the monitor from waking? It sounds as if
resetting the BIOS depends on what model the computer is. Macs have
PRAMs and CUDAs instead. The PRAM can be reset with keyboard
combination on atartup. The CUDA includes the pram and is reset with an
electrical switch. I don't think either can keep the monitor from
showing a green light.

Michael Kennedy wrote:

It won't ask for memory. You have to have memory in the pc for it to do
anything but beep. That's all you'll get without memory BEEEP BEEEP
BEEEP.... If you take everything out except the processor it should
beep..(including memory and vid card) Beeping a good sign and and means the
bios is working.

- Mike

"James Sweet" wrote in message
news:Zmlze.14689$Yb4.6535@trnddc08...

"jakdedert" wrote in message
news

"Choreboy" wrote in message
...
Neighbors have a computer that won't work after a lightning strike.
With the video cable connected, the monitor stays black and in the
standby mode. There are howls from the speakers, like feedback. With
the cable disconnected, the monitor will briefly show a notice that
it's
not connected. There are no howls from the speakers although the mic
cable remains connected.

With the power off, I checked the pins of the monitor cable to see that
the grounding pins were grounded and the signal pins were not. One
grounding pin is open, so it seems certain that the monitor is damaged.

The next step would be to try another monitor to see if there's other
damage to the system. In case the computer's video card is damaged,
can
a monitor be damaged by plugging in to it?

'Probably' not, but why not try plugging their monitor into your
computer?
That's extremely unlikely to cause any damage. Then, I'd take
*everything*
out of the neighbor's computer, except the vid card...unplug memory, all
drives including floppy...just leave in the CPU and vid card.



Actually I'd be more concerned about that causing damage than the other
way
around, but realistically either way should be fine.

I got 75 on the R, G, and B signal pins. Without a schematic, I
wondered if the sync pin was fed by a transformer, in which case zero
ohms could have been correct.

When I checked the monitor pins, a scope showed several problems. A
local drugstore chain has refurbished computers and monitors similar to
theirs for $250. Why fix it?


Personally I'd give it a shot just because I can, but you're right in that
it's not worth spending a great deal of time or money on it.

"Choreboy" wrote in message
...
My own computer is a Mac. I think with a Mac, the display comes up
before it checks the memory. On a PC, would bad memory keep the monitor
light from turning green?



It can, it really depends on the fault though. If the RAM is bad in a
location that prevents the POST from running then the display adapter will
never be initialized. Seems I've had Macs with bad enough RAM that they
wouldn't show anything on the screen either but I haven't had a ton of
exposure to the recent ones.

James Sweet wrote:

"Choreboy" wrote in message
...
My own computer is a Mac. I think with a Mac, the display comes up
before it checks the memory. On a PC, would bad memory keep the monitor
light from turning green?


It can, it really depends on the fault though. If the RAM is bad in a
location that prevents the POST from running then the display adapter will
never be initialized. Seems I've had Macs with bad enough RAM that they
wouldn't show anything on the screen either but I haven't had a ton of
exposure to the recent ones.

Well, a man more familiar with PCs got the display going by removing the
CPU and plugging it back in. I suppose in each case where I'd found an
open ground on the computer or monitor, its counterpart supplied the
necessary ground. He found it still needs a new motherboard.

James Sweet wrote:


I got 75 on the R, G, and B signal pins. Without a schematic, I
wondered if the sync pin was fed by a transformer, in which case zero
ohms could have been correct.

When I checked the monitor pins, a scope showed several problems. A
local drugstore chain has refurbished computers and monitors similar to
theirs for $250. Why fix it?

Personally I'd give it a shot just because I can, but you're right in that
it's not worth spending a great deal of time or money on it.

A motherboard was $52 with shipping.