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Flat Screen Monitor went Black
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elect...@online.com
Jan 25, 2015, 10:00:44 PM1/25/15
to
I was on my computer when my Flat Screen Monitor went black. Just
suddenly black, no prior indication of a problem. It's a HP 1740.
As far as I know, this monitor has a florescent bulb to light it.
I'm thinking the bulb died, but I'm noticing that the indicator LED is
now flashing, not solid "ON". This light is right next to the ON-OFF
power switch.
Pushing the ON-OFF switch does not seem to shut it off either. I
unplugged it, then plugged it back in and that light just flashes. This
makes me think that something else in the circuitry fried. (Just a
guess). It would seem to me that if it was just the bulb, everything
else would function normally. But I've never worked on one of these
monitors, so I dont really know.
I do have electronics knowledge, and used to work on Tv sets and the old
CRT monitors, but it's been years.....
So far I have not even been able to get inside this thing. I got the
plastic case off, and now there's a metal case, which has screws along
the edge, but then there are wires or plastic strips that hold the shell
together.
If it just needs a bulb and they are not too costly, I may fix it, but
if it's more than that, I'll just trash it. But just for the heck of
it, I want to get inside of it. The problem with stuff built like this,
is that as the layers come apart, flat ribbon cables need to be
unplugged. Even if I can get it apart, how the hell can anyone test
them, when stuff is unplugged. Ideally, it could still be plugged in,
and I could measure voltages, etc.... That dont seem possible. I
suppose like most modern electronics, it's just a throw away item.
This is almost worse than taking apart my laptop computer.
If by chance I can get it open without destroying it in the process, is
there a way to test the bulb? Is there a way to test the whole unit
without having layers plugged in to those ribbon cables.
It looks to me like this is one of those factory only repairs, where
they know exactly how to disassemble it, and have extension cables for
those ribbon cables, and special tools to open the case.
It's stuff like this that made me quit repairing electronics. The old
stuff was so much easier to work on. Even the old vacuum tube stuff.
(I guess I'm showing my age)! :)
Thanks in advance for all help!
suddenly black, no prior indication of a problem. It's a HP 1740.
As far as I know, this monitor has a florescent bulb to light it.
I'm thinking the bulb died, but I'm noticing that the indicator LED is
now flashing, not solid "ON". This light is right next to the ON-OFF
power switch.
Pushing the ON-OFF switch does not seem to shut it off either. I
unplugged it, then plugged it back in and that light just flashes. This
makes me think that something else in the circuitry fried. (Just a
guess). It would seem to me that if it was just the bulb, everything
else would function normally. But I've never worked on one of these
monitors, so I dont really know.
I do have electronics knowledge, and used to work on Tv sets and the old
CRT monitors, but it's been years.....
So far I have not even been able to get inside this thing. I got the
plastic case off, and now there's a metal case, which has screws along
the edge, but then there are wires or plastic strips that hold the shell
together.
If it just needs a bulb and they are not too costly, I may fix it, but
if it's more than that, I'll just trash it. But just for the heck of
it, I want to get inside of it. The problem with stuff built like this,
is that as the layers come apart, flat ribbon cables need to be
unplugged. Even if I can get it apart, how the hell can anyone test
them, when stuff is unplugged. Ideally, it could still be plugged in,
and I could measure voltages, etc.... That dont seem possible. I
suppose like most modern electronics, it's just a throw away item.
This is almost worse than taking apart my laptop computer.
If by chance I can get it open without destroying it in the process, is
there a way to test the bulb? Is there a way to test the whole unit
without having layers plugged in to those ribbon cables.
It looks to me like this is one of those factory only repairs, where
they know exactly how to disassemble it, and have extension cables for
those ribbon cables, and special tools to open the case.
It's stuff like this that made me quit repairing electronics. The old
stuff was so much easier to work on. Even the old vacuum tube stuff.
(I guess I'm showing my age)! :)
Thanks in advance for all help!
Knoppix User
Jan 25, 2015, 10:21:38 PM1/25/15
to
LEDS backlighting the unit.
Like you I recall burning myself on tubes even before hybrids.
I'll just try reflowing some stuff and continuity testing the lighting
circuits however your problem seems rather more complicated.
I googled the info to pull mine apart.
If I cannot figure it out and fix it in 2 hrs. out to the trash she goes.
I've several adaquate units scored from the thrift stores as well as four
CRTs
John Keiser
Jan 25, 2015, 10:51:23 PM1/25/15
to
I am just a DIYer but have fixed many flat screen monitors, not HP.
The cause is often a bad cap.
So common, Ebay even has kits for the parts [for Dells, at least].
I have an ESR meter but you can usually visually see the bad cap.
You might as well spend the extra 15 minutes and remove the metal shielding
and look for bad caps.
"Knoppix User" <fa...@nothere.com> wrote in message
news:3pixw.1209173$UR.9...@fx04.iad...
The cause is often a bad cap.
So common, Ebay even has kits for the parts [for Dells, at least].
I have an ESR meter but you can usually visually see the bad cap.
You might as well spend the extra 15 minutes and remove the metal shielding
and look for bad caps.
"Knoppix User" <fa...@nothere.com> wrote in message
news:3pixw.1209173$UR.9...@fx04.iad...
mike
Jan 25, 2015, 11:07:45 PM1/25/15
to
On 1/25/2015 7:51 PM, John Keiser wrote:
> I am just a DIYer but have fixed many flat screen monitors, not HP.
> The cause is often a bad cap.
> So common, Ebay even has kits for the parts [for Dells, at least].
> I have an ESR meter but you can usually visually see the bad cap.
> You might as well spend the extra 15 minutes and remove the metal shielding
> and look for bad caps.
Change all the caps.
> I am just a DIYer but have fixed many flat screen monitors, not HP.
> The cause is often a bad cap.
> So common, Ebay even has kits for the parts [for Dells, at least].
> I have an ESR meter but you can usually visually see the bad cap.
> You might as well spend the extra 15 minutes and remove the metal shielding
> and look for bad caps.
More than once, I've decided that some of the caps have OK ESR.
Six months later, taking it apart to change them too.
Also, unplug the thing and leave it unplugged.
As the caps resistance goes up, the voltage spike increases.
Your voltmeter still
reads nominal voltage, cuz that's still the average voltage. Put a
scope on it
and you see a very different picture.
You can get 20V spikes on the 3.3V supply.
The Graphics Chips
don't like that and will short. Then, you've got a brick.
Jeff Liebermann
Jan 26, 2015, 1:11:50 AM1/26/15
to
On Sun, 25 Jan 2015 20:57:36 -0600, elect...@online.com wrote:
>I was on my computer when my Flat Screen Monitor went black. Just
>suddenly black, no prior indication of a problem. It's a HP 1740.
It's probably not the CCFL tubes but rather the capacitors in the
>I was on my computer when my Flat Screen Monitor went black. Just
>suddenly black, no prior indication of a problem. It's a HP 1740.
inverter section, which is built onto the power supply PCB.
Thank you for including the model number. Please double check the
muddle number as it can be a 1740 or an L1740 display. If you're not
sure, tear it open and compare the photos in the following links.
There are also different mutations of the PCB.
You can buy a recap (capacitor replacement) kit for about $7.00:
<http://www.ebay.com/itm/330506313562> (L1740)
<http://www.ebay.com/itm/330502333292> (1740)
There are other kits for replacing the semiconductors, which sometimes
also blow up. If you don't feel like doing the repair, you can also
get PCB's rather cheaply:
<http://www.ebay.com/sch/i.html?_nkw=hp+1740+board>
Again, notice the different PCB mutations.
You will probably find the PCB between the two big xformers to be
overheated and scorched. If the PCB crumbles, take some epoxy and
rebuild the burnt area. Use your imagination for how to rework the
PCB traces. With a single sided board, this should be easy.
Hint: Take some digital photos as you go along so that you can put it
back together without extra screws, etc.
Good luck.
--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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