LCD Monitor Problem - Turns on and off

[Bill Simpson]

I tried to post this yesterday, but it didn't seem to show up.
Apologies if it's duplicated. Probably a Comcast problem.

I have a very unusual problem with an LCD monitor. I will try and be
descriptive as possible without being confusing.

When the adapter for the monitor is plugged directly into a wall
outlet, and there is always current to the wall outlet, I can turn the
monitor on and off normally. There are no problems.

When the adapter for the monitor is connected to my UPS and the UPS is
turned off and then back on, or when the adapter is plugged into a
wall outlet and then unplugged from the wall outlet and plugged back
in, I begin to have problems.

Specifically, in the two situations above, when booting the computer,
the monitor will "buzz" briefly, the picture will come on, and then go
off. It will do this several times during the boot sequence. It will
do it once at the bios, once at the Windows splash and then again at
the login screen. Upon each of the three occurrences mentioned, the
monitor will "buzz", the picture will come on briefly and then go off.

However…if I reboot the system several times, or when I'm at the last
login screen, turn the monitor on and off several times with its
switch, it will eventually stay on.

I have tested this monitor with different video cards and on different
systems, so it's not the video card or one specific box.

From the way the LCD is reacting, the problem seems to be similar to a
bad ballast in a fluorescent light, is this possible?

Any suggestions (except leave it plugged in all the time? Is there any
way to test this LCD with minimum equipment and knowledge?

Thanks in advance.

 

[mistermaniac]

I tried to post this yesterday, but it didn't seem to show up.
Apologies if it's duplicated. Probably a Comcast problem.

I have a very unusual problem with an LCD monitor. I will try and be
descriptive as possible without being confusing.

When the adapter for the monitor is plugged directly into a wall
outlet, and there is always current to the wall outlet, I can turn the
monitor on and off normally. There are no problems.

When the adapter for the monitor is connected to my UPS and the UPS is
turned off and then back on, or when the adapter is plugged into a
wall outlet and then unplugged from the wall outlet and plugged back
in, I begin to have problems.

Specifically, in the two situations above, when booting the computer,
the monitor will "buzz" briefly, the picture will come on, and then go
off. It will do this several times during the boot sequence. It will
do it once at the bios, once at the Windows splash and then again at
the login screen. Upon each of the three occurrences mentioned, the
monitor will "buzz", the picture will come on briefly and then go off.

However…if I reboot the system several times, or when I'm at the last
login screen, turn the monitor on and off several times with its
switch, it will eventually stay on.

I have tested this monitor with different video cards and on different
systems, so it's not the video card or one specific box.

From the way the LCD is reacting, the problem seems to be similar to a
bad ballast in a fluorescent light, is this possible?

Any suggestions (except leave it plugged in all the time? Is there any
way to test this LCD with minimum equipment and knowledge?

Thanks in advance.

When the screen goes "off" does it really goes off? It sounds like
bad inverter or a bad ccfl

 

[Arfa Daily]

When the screen goes "off" does it really goes off? It sounds like a
bad inverter or a bad ccfl.

Yes, you need to establish this. It is very possible, if the monitor is
genuinely not starting after a period of being totally unpowered, that the
problem is actually the external power supply, which is pretty much certain
to be a switch mode type. I have had a number of these giving similar
symptoms to those you state, the cause being bad electrolytics, particularly
on the primary side. In general, when switchers have this sort of problem,
once you've persuaded them to come on, and the caps have warmed up a bit,
they will stay on. Try measuring the output voltage of the power supply,
after it's been off for a couple of hours. You may well find that there
isn't any, or what there is, is pulsing. You could also try hanging a low
wattage car bulb across the power supply output - say an interior light
bulb - if you can figure a way of getting a connection to the output plug.

Arfa

 

[tvguy]

It don`t sound like a bad inverter if it is running good when plugge
directly to the wall outlet. If it only does this when plugged int
the powersupply of the computer then this would be a problem of th
computers powersupply. Did you try to plug it into another compute
to see if you still have the same problem ? I would suggest to tr
this first and see what happens

mistermaniacwrote

I tried to post this yesterday, but it didn't seem to show up
Apologies if it's duplicated. Probably a Comcast problem

I have a very unusual problem with an LCD monitor. I will try an b
descriptive as possible without being confusing

When the adapter for the monitor is plugged directly into a wal
outlet, and there is always current to the wall outlet, I can tur th
monitor on and off normally. There are no problems

When the adapter for the monitor is connected to my UPS and the UP i
turned off and then back on, or when the adapter is plugged into
wall outlet and then unplugged from the wall outlet and plugge bac
in, I begin to have problems

Specifically, in the two situations above, when booting th computer
the monitor will "buzz" briefly, the picture will come on and then g
off. It will do this several times during the boot sequence. I wil
do it once at the bios, once at the Windows splash and then agai a
the login screen. Upon each of the three occurrences mentioned th
monitor will "buzz", the picture will come on briefly an then go off

However…if I reboot the system several times, or when I'm at th las
login screen, turn the monitor on and off several times with it
switch, it will eventually stay on

I have tested this monitor with different video cards and o differen
systems, so it's not the video card or one specific box

From the way the LCD is reacting, the problem seems to be similar t

bad ballast in a fluorescent light, is this possible

Any suggestions (except leave it plugged in all the time? Is ther an
way to test this LCD with minimum equipment and knowledge

Thanks in advance

When the screen goes "off" does it really goes off? I
sounds like
bad inverter or a bad ccfl

 

[Arfa Daily]

It don`t sound like a bad inverter if it is running good when plugged
directly to the wall outlet. If it only does this when plugged into
the powersupply of the computer then this would be a problem of the
computers powersupply. Did you try to plug it into another computer
to see if you still have the same problem ? I would suggest to try
this first and see what happens.

Maybe I read it wrong, but I don't think that this is what the guy was
saying. I read it as he was always using the external power unit, that came
with the LCD monitor, and if he left it plugged in the wall, ie with power
always available to this power supply, but with the monitor turned off, when
he came to switch the monitor on, it came on ok. If, however, he plugged in
to any power source that was turned off for periods of time eg his UPS, or
unplugged from the wall for any length of time, then when he came to put
power back on the PSU, and then tried immediately to switch on the monitor,
he got the buzzing, spitting failure to start up, which is typical of a
defective switching PSU, with bad electrolytics. Perhaps the OP can confirm
??

If this is actually the case, then all the stuff about Windows and rebooting
etc is probably a red herring. It just relates to the length of time all
this takes, which gives the power supply time to struggle to a startup.

Arfa

 

[Bill Simpson]

On Sat, 04 Mar 2006 18:57:30 GMT, "Arfa Daily"

What you described is precisely what is happening. What you said
about the boot process being a Red Herring, I believe is correct.
Thanks to the rest of your for your help, apologies for the difficulty
in description.

Do you suggest that I first test the output of the power supply?

Thanks again

 

[tvguy]

Arfa Dailywrote

It don`t sound like a bad inverter if it is running good whe plugge
directly to the wall outlet. If it only does this when plugged int
the powersupply of the computer then this would be a problem of th
computers powersupply. Did you try to plug it into another compute
to see if you still have the same problem ? I would suggest to tr
this first and see what happens


Maybe I read it wrong, but I don't think that this is what the gu

wa
saying. I read it as he was always using the external power unit, tha
came
with the LCD monitor, and if he left it plugged in the wall, ie wit
power
always available to this power supply, but with the monitor turne
off, when
he came to switch the monitor on, it came on ok. If, however, h
plugged in
to any power source that was turned off for periods of time eg hi
UPS, or
unplugged from the wall for any length of time, then when he came t
put
power back on the PSU, and then tried immediately to switch on th
monitor,
he got the buzzing, spitting failure to start up, which is typical o
a
defective switching PSU, with bad electrolytics. Perhaps the OP ca
confirm
?

If this is actually the case, then all the stuff about Windows an
rebooting
etc is probably a red herring. It just relates to the length of tim
all
this takes, which gives the power supply time to struggle to
startup

Arfa[/quote:733e2a47e2

If that was what he was stating. I may have read his post wrong t
what he was trying to say. Then I would have to say yes that he ha
something wrong with the external powersupply

 

[Arfa Daily]

Arfa Dailywrote:

It don`t sound like a bad inverter if it is running good when plugged
directly to the wall outlet. If it only does this when plugged into
the powersupply of the computer then this would be a problem of the
computers powersupply. Did you try to plug it into another computer
to see if you still have the same problem ? I would suggest to try
this first and see what happens.


Maybe I read it wrong, but I don't think that this is what the guy

was
saying. I read it as he was always using the external power unit, that
came
with the LCD monitor, and if he left it plugged in the wall, ie with
power
always available to this power supply, but with the monitor turned
off, when
he came to switch the monitor on, it came on ok. If, however, he
plugged in
to any power source that was turned off for periods of time eg his
UPS, or
unplugged from the wall for any length of time, then when he came to
put
power back on the PSU, and then tried immediately to switch on the
monitor,
he got the buzzing, spitting failure to start up, which is typical of
a
defective switching PSU, with bad electrolytics. Perhaps the OP can
confirm
??

If this is actually the case, then all the stuff about Windows and
rebooting
etc is probably a red herring. It just relates to the length of time
all
this takes, which gives the power supply time to struggle to a
startup.

Arfa[/quote:733e2a47e2]

If that was what he was stating. I may have read his post wrong to
what he was trying to say. Then I would have to say yes that he has
something wrong with the external powersupply.

Yeah, I think that's what he's saying, tvguy - see his additional post
above.

Bill.

I think me and tvguy are now both in agreement. Yes, go for power supply
trouble. I had a FAX machine on my bench last week, which was powered from
an external 24v 1500mA switch mode supply. If left on, it would work for
ever. However, if left unpowered for a few hours, when put back on, the
power supply would struggle for about a minute, to start up.

Once I got inside it, it was fairly obvious that the two series-connected
82k startup resistors were pretty distressed and high. I replaced both these
( they use two in series to double the voltage rating of these small film
resistors ). Also, there was a single 220uF cap on the primary side. When
checked on my ESR meter, this went 38 ohms, which is way, way too high, so
this item was replaced as well. The supply then started up first time, every
time, no matter how long it had been off. Both of the mentioned components
are very common for causing startup trouble in any switcher.

Just a word of warning. If you are not used to switchers, be very very
mindful of your personal safety. This type of supply is VERY dangerous, and
could be lethal. Remember also, that the main smoothing cap will charge to
almost one and a half times your local input voltage. If the supply doesn't
start up, this cap will likely stay charged to very close on this figure for
hours, as most switchers do not employ a leak resistor across it. I would
always recommend having these supplies connected to a bench isolation
transformer, when they are opened to be worked on.

Arfa

 

[Bill Simpson]

On Sat, 04 Mar 2006 18:57:30 GMT, "Arfa Daily"

Tried posting this earlier, hope this isn't double posted, problems
again with my ISP. Hope I haven't lost the thread.

What you described is precisely what is happening. What you said
about the boot process being a Red Herring, I believe is correct.
Thanks to the rest of your for your help, apologies for the difficulty
in description.

Do you suggest that I first test the output of the power supply?

Thanks again

 

[Bill Simpson]

On Mon, 06 Mar 2006 09:03:42 GMT, "Arfa Daily"

I see that my reply did get double posted. Thanks for the very
precise information. With my rather low level of technical knowledge,
do you think it more advisable that I just replace the power supply?

The power supply that I currently have is

Sunny
Input :100-240 - 1.6A Max, 50-60Hz, 70-80VA
Output: +12V - 4.0A

I contacted the manufacturer of the monitor and they want $75 for a
replacement power supply (More on that later). I've found some others,
more reasonably priced online. One is a 12V 5A (60W) and the other is
a 12V 4.16A (50W). Am I correct in assuming that both should work?
If the connector is different in these power supplies, would cutting
and soldering the original connector to the new power supply be
acceptable rather than the more complicated and dangerous course that
professionals with your expertise would take? I know it's a crude
solution, but it's something I would feel comfortable with.

The rest if off topic, but if you have some time, I would like your
opinion. I had mentioned earlier that I contacted the manufacturer
about a new power supply. I went to their home page and read the FAQ
ahead of time. I found this in the FAQ:

"My screen comes on for a second and then goes black. How do I resolve
this issue?

1. Please contact Customer Service for further assistance at
323-346-0888. There is a possible short in the ac adapter. "

It seems that the manufacturer knew about this problem for some time.
I had registered my monitor and asked the representative when I called
why they hadn't notified me of the problem (As the warranty on the
montitor had just run out). I also asked if this wasn't a potential
fire hazard. I got a typical rebuff. My question is: Could a short
in the power supply cause a fire? I this a dangerous situation or
would normal internal safeguards kept anything hazardous from
happening?

Thanks again for all of the expert help. You all went above and
beyond what I expected.

Arfa Dailywrote:

It don`t sound like a bad inverter if it is running good when plugged
directly to the wall outlet. If it only does this when plugged into
the powersupply of the computer then this would be a problem of the
computers powersupply. Did you try to plug it into another computer
to see if you still have the same problem ? I would suggest to try
this first and see what happens.


Maybe I read it wrong, but I don't think that this is what the guy

was
saying. I read it as he was always using the external power unit, that
came
with the LCD monitor, and if he left it plugged in the wall, ie with
power
always available to this power supply, but with the monitor turned
off, when
he came to switch the monitor on, it came on ok. If, however, he
plugged in
to any power source that was turned off for periods of time eg his
UPS, or
unplugged from the wall for any length of time, then when he came to
put
power back on the PSU, and then tried immediately to switch on the
monitor,
he got the buzzing, spitting failure to start up, which is typical of
a
defective switching PSU, with bad electrolytics. Perhaps the OP can
confirm
??

If this is actually the case, then all the stuff about Windows and
rebooting
etc is probably a red herring. It just relates to the length of time
all
this takes, which gives the power supply time to struggle to a
startup.

Arfa[/quote:733e2a47e2]

If that was what he was stating. I may have read his post wrong to
what he was trying to say. Then I would have to say yes that he has
something wrong with the external powersupply.

Yeah, I think that's what he's saying, tvguy - see his additional post
above.

Bill.

I think me and tvguy are now both in agreement. Yes, go for power supply
trouble. I had a FAX machine on my bench last week, which was powered from
an external 24v 1500mA switch mode supply. If left on, it would work for
ever. However, if left unpowered for a few hours, when put back on, the
power supply would struggle for about a minute, to start up.

Once I got inside it, it was fairly obvious that the two series-connected
82k startup resistors were pretty distressed and high. I replaced both these
( they use two in series to double the voltage rating of these small film
resistors ). Also, there was a single 220uF cap on the primary side. When
checked on my ESR meter, this went 38 ohms, which is way, way too high, so
this item was replaced as well. The supply then started up first time, every
time, no matter how long it had been off. Both of the mentioned components
are very common for causing startup trouble in any switcher.

Just a word of warning. If you are not used to switchers, be very very
mindful of your personal safety. This type of supply is VERY dangerous, and
could be lethal. Remember also, that the main smoothing cap will charge to
almost one and a half times your local input voltage. If the supply doesn't
start up, this cap will likely stay charged to very close on this figure for
hours, as most switchers do not employ a leak resistor across it. I would
always recommend having these supplies connected to a bench isolation
transformer, when they are opened to be worked on.

Arfa

 

[Arfa Daily]

On Mon, 06 Mar 2006 09:03:42 GMT, "Arfa Daily"

I see that my reply did get double posted. Thanks for the very
precise information. With my rather low level of technical knowledge,
do you think it more advisable that I just replace the power supply?

The power supply that I currently have is

Sunny
Input :100-240 - 1.6A Max, 50-60Hz, 70-80VA
Output: +12V - 4.0A

I contacted the manufacturer of the monitor and they want $75 for a
replacement power supply (More on that later). I've found some others,
more reasonably priced online. One is a 12V 5A (60W) and the other is
a 12V 4.16A (50W). Am I correct in assuming that both should work?
If the connector is different in these power supplies, would cutting
and soldering the original connector to the new power supply be
acceptable rather than the more complicated and dangerous course that
professionals with your expertise would take? I know it's a crude
solution, but it's something I would feel comfortable with.

The rest if off topic, but if you have some time, I would like your
opinion. I had mentioned earlier that I contacted the manufacturer
about a new power supply. I went to their home page and read the FAQ
ahead of time. I found this in the FAQ:

"My screen comes on for a second and then goes black. How do I resolve
this issue?

1. Please contact Customer Service for further assistance at
323-346-0888. There is a possible short in the ac adapter. "

It seems that the manufacturer knew about this problem for some time.
I had registered my monitor and asked the representative when I called
why they hadn't notified me of the problem (As the warranty on the
montitor had just run out). I also asked if this wasn't a potential
fire hazard. I got a typical rebuff. My question is: Could a short
in the power supply cause a fire? I this a dangerous situation or
would normal internal safeguards kept anything hazardous from
happening?

Thanks again for all of the expert help. You all went above and
beyond what I expected.

Bill

If you don't feel qualified to go inside the supply, then I would not be
comfortable advising you to do so. The fault almost certainly will be one of
the things I suggested, but it's not worth risking injury to try to repair
it, if you're not absolutely confident of what you're doing.

Either of the two power supplies should be ok rating-wise. Any power supply
with a rating of 4 amps, will be a switch mode type, so by very nature will
be regulated to its declared 12v output.
Cutting and joining on the output lead is fine, BUT make absolutely sure
that you get the polarity the same as original. The monitor will not like
having reverse polarity DC shoved up it ...

If ever I join wires in this way, I always use heatshrink sleeving, which
you could probably get from your local Radio Shack. It shrinks easily with a
small paint stripper gun on 'low', and does a nice neat job of re-insulating
the cable, and reinforcing the join.

As far as the manufacturer's statement about a " short in the power supply "
goes, it's probably a bit of generic techno-babble that means nothing more
than ' a faulty power supply '. Joe public can equate with a " short ". It
sounds just technical enough to be describing something real, but is
basically meaningless in this context. It is unlikely that any fire would
ensue from any of the typical ( and much more likely ) faults that the power
supply would really be suffering from. It's probably just a typical switch
mode power supply design issue, where whover laid out the board, decided, as
they always seem to, to place an important cap right next to a resistor that
gets hot. It probably just happens that the fallout from this has been
particularly bad for this manufacturer, using this ( almost certainly
bought-in ) power supply on his particular product.

Arfa

 

[Bill Simpson]

Thanks for all the help. Since you introduced the concerns about
maintaining the proper polarity. Is there a simple way to verify
this? I recently pick up a new Greenlee DM-810 True RMS Digital
Multimeter at a garage sale for $5. Does this have a function that
would test polarity?

 

[Arfa Daily]

Thanks for all the help. Since you introduced the concerns about
maintaining the proper polarity. Is there a simple way to verify
this? I recently pick up a new Greenlee DM-810 True RMS Digital
Multimeter at a garage sale for $5. Does this have a function that
would test polarity?

Bill, I'm assuming that this is a digital meter - yes ? OK. Making sure that
you have the red probe in the red socket, and the black in the black socket,
then just go ahead and measure the output. If you have your red lead
connected to the positive output wire, then the meter will just
read " 12.00 " or whatever. If you have your red lead connected to the
negative output wire, then the meter will read " - 12.00 " ie a minus sign
at the front of the number.

As additional confirmation, the original power supply may well have a little
picture of the output connector, indicating polarity, as might the monitor
by its input socket. Additionally, as any replacement you buy is likely just
a generic type, it will probably also have a picture of its plug, indicating
polarity. For what it's worth, you very likely will not have to do any
cutting and grafting. In general, there seems to be a loose " standard " on
the plug size and polarity sense, employed by the current crop of externally
powered LCD monitors and TVs. But that said, I emphasise, better to be safe
than sorry ...

Arfa

 

[Bill Simpson]

Thanks again Arfa...I think we're done.

Bill

 

[Arfa Daily]

No probs, Bill. Glad we were able to help you.

Arfa

 

[[email protected]]

I tried to post this yesterday, but it didn't seem to show up.
Apologies if it's duplicated. Probably a Comcast problem.

I have a very unusual problem with an LCD monitor. I will try and be
descriptive as possible without being confusing.

When the adapter for the monitor is plugged directly into a wall
outlet, and there is always current to the wall outlet, I can turn the
monitor on and off normally. There are no problems.

When the adapter for the monitor is connected to my UPS and the UPS is
turned off and then back on, or when the adapter is plugged into a
wall outlet and then unplugged from the wall outlet and plugged back
in, I begin to have problems.

Specifically, in the two situations above, when booting the computer,
the monitor will "buzz" briefly, the picture will come on, and then go
off. It will do this several times during the boot sequence. It will
do it once at the bios, once at the Windows splash and then again at
the login screen. Upon each of the three occurrences mentioned, the
monitor will "buzz", the picture will come on briefly and then go off.

However...if I reboot the system several times, or when I'm at the last
login screen, turn the monitor on and off several times with its
switch, it will eventually stay on.

I have tested this monitor with different video cards and on different
systems, so it's not the video card or one specific box.

From the way the LCD is reacting, the problem seems to be similar to a
bad ballast in a fluorescent light, is this possible?

Any suggestions (except leave it plugged in all the time? Is there any
way to test this LCD with minimum equipment and knowledge?

Thanks in advance.