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Samsung LCD monitor: screen blanks after 1 second
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Percival P. Cassidy
Oct 21, 2015, 12:31:28 PM10/21/15
to
This is a SyncMaster 2233SW that worked fine for years, but then the
image disappeared. Further investigation showed that the image would
display for just a second or so after power-up or after switching
inputs. So: looks like classic defective-power-supply problem, probably
resulting from crappy electrolytic capacitors.
When I took it apart I found that there were bulging caps and a
partially discolored PC board.
Since the PC board itself showed signs of overheating, I thought it
better to look for a replacement power-supply module than to simply
replace the electrolytics on the old one. I bought one on eBay that was
described as having come from a monitor with a cracked screen. It had no
sign of bulging capacitors or overheating, but it did not solve the
problem. The seller refunded my money and did not want the apparently
defective unit returned, so I got a set of replacement capacitors for
that one. BUT that has still not solved the problem: with two different
computers, whether I use the analog or the digital input, there is an
image for just one second or so. AND I do not see any trace of an image
when I shine a light onto the screen either.
I cannot find a service manual for this monitor -- at least not without
sending money to a person or business of unknown integrity.
Where do I go from here?
Perce
image disappeared. Further investigation showed that the image would
display for just a second or so after power-up or after switching
inputs. So: looks like classic defective-power-supply problem, probably
resulting from crappy electrolytic capacitors.
When I took it apart I found that there were bulging caps and a
partially discolored PC board.
Since the PC board itself showed signs of overheating, I thought it
better to look for a replacement power-supply module than to simply
replace the electrolytics on the old one. I bought one on eBay that was
described as having come from a monitor with a cracked screen. It had no
sign of bulging capacitors or overheating, but it did not solve the
problem. The seller refunded my money and did not want the apparently
defective unit returned, so I got a set of replacement capacitors for
that one. BUT that has still not solved the problem: with two different
computers, whether I use the analog or the digital input, there is an
image for just one second or so. AND I do not see any trace of an image
when I shine a light onto the screen either.
I cannot find a service manual for this monitor -- at least not without
sending money to a person or business of unknown integrity.
Where do I go from here?
Perce
mike
Oct 21, 2015, 2:20:04 PM10/21/15
to
a problem with the backlight.
I fixed one of those with a new transformer, but the first one of
those shipped to me with an open secondary. Second one worked.
I "fixed" a second monitor by disabling the protection chip.
I wouldn't recommend that to anyone else tho...
If the backlight is on a different board, you may find something
there.
It's possible that the new board had the same failure mode.
Normally, you'd expect the image to stay up even if the backlight
turns off, but who knows what the designer decided on that model.
Had one monitor that had a bad cap in the 5V. Supply.
The spikes on the 5V caused the controller chip to malfunction
and lock up.
Probe around with a digital storage scope to see what happens
on power up.
Percival P. Cassidy
Oct 22, 2015, 9:09:05 AM10/22/15
to
On 10/21/2015 02:19 PM, mike wrote:
>> This is a SyncMaster 2233SW that worked fine for years, but then the
>> image disappeared. Further investigation showed that the image would
>> display for just a second or so after power-up or after switching
>> inputs. So: looks like classic defective-power-supply problem, probably
>> resulting from crappy electrolytic capacitors.
>>
>> When I took it apart I found that there were bulging caps and a
>> partially discolored PC board.
>>
>> Since the PC board itself showed signs of overheating, I thought it
>> better to look for a replacement power-supply module than to simply
>> replace the electrolytics on the old one. I bought one on eBay that was
>> described as having come from a monitor with a cracked screen. It had no
>> sign of bulging capacitors or overheating, but it did not solve the
>> problem. The seller refunded my money and did not want the apparently
>> defective unit returned, so I got a set of replacement capacitors for
>> that one. BUT that has still not solved the problem: with two different
>> computers, whether I use the analog or the digital input, there is an
>> image for just one second or so. AND I do not see any trace of an image
>> when I shine a light onto the screen either.
>>
>> I cannot find a service manual for this monitor -- at least not without
>> sending money to a person or business of unknown integrity.
>>
>> Where do I go from here?
>> This is a SyncMaster 2233SW that worked fine for years, but then the
>> image disappeared. Further investigation showed that the image would
>> display for just a second or so after power-up or after switching
>> inputs. So: looks like classic defective-power-supply problem, probably
>> resulting from crappy electrolytic capacitors.
>>
>> When I took it apart I found that there were bulging caps and a
>> partially discolored PC board.
>>
>> Since the PC board itself showed signs of overheating, I thought it
>> better to look for a replacement power-supply module than to simply
>> replace the electrolytics on the old one. I bought one on eBay that was
>> described as having come from a monitor with a cracked screen. It had no
>> sign of bulging capacitors or overheating, but it did not solve the
>> problem. The seller refunded my money and did not want the apparently
>> defective unit returned, so I got a set of replacement capacitors for
>> that one. BUT that has still not solved the problem: with two different
>> computers, whether I use the analog or the digital input, there is an
>> image for just one second or so. AND I do not see any trace of an image
>> when I shine a light onto the screen either.
>>
>> I cannot find a service manual for this monitor -- at least not without
>> sending money to a person or business of unknown integrity.
>>
>> Where do I go from here?
> There's typically a sensor that shuts down the backlight if it senses
> a problem with the backlight.
> I fixed one of those with a new transformer, but the first one of
> those shipped to me with an open secondary. Second one worked.
>
> I "fixed" a second monitor by disabling the protection chip.
> I wouldn't recommend that to anyone else tho...
>
> If the backlight is on a different board, you may find something
> there.
> It's possible that the new board had the same failure mode.
>
> Normally, you'd expect the image to stay up even if the backlight
> turns off, but who knows what the designer decided on that model.
>
> Had one monitor that had a bad cap in the 5V. Supply.
> The spikes on the 5V caused the controller chip to malfunction
> and lock up.
>
> Probe around with a digital storage scope to see what happens
> on power up.
I neither own nor have access to any kind of scope.
> a problem with the backlight.
> I fixed one of those with a new transformer, but the first one of
> those shipped to me with an open secondary. Second one worked.
>
> I "fixed" a second monitor by disabling the protection chip.
> I wouldn't recommend that to anyone else tho...
>
> If the backlight is on a different board, you may find something
> there.
> It's possible that the new board had the same failure mode.
>
> Normally, you'd expect the image to stay up even if the backlight
> turns off, but who knows what the designer decided on that model.
>
> Had one monitor that had a bad cap in the 5V. Supply.
> The spikes on the 5V caused the controller chip to malfunction
> and lock up.
>
> Probe around with a digital storage scope to see what happens
> on power up.
The power module has connectors for four 2-wire leads that run to one
vertical edge of the screen, and another connector from which a
multi-conductor lead (more than 2 conductors, but I don't recall how
many, and it's not open at the moment for me to look) going to the
bottom edge of the screen (perhaps to the control buttons?). There is
another module that has the analog and digital signal connectors, a
multi-connector lead from the power module, and a shielded
multi-connector lead going to the top edge of the screen.
Perce
mako...@yahoo.com
Oct 22, 2015, 2:15:36 PM10/22/15
to
> >
> > If the backlight is on a different board, you may find something
> > there.
> > It's possible that the new board had the same failure mode.
> >
> > Normally, you'd expect the image to stay up even if the backlight
> > turns off, but who knows what the designer decided on that model.
> >
> > Had one monitor that had a bad cap in the 5V. Supply.
> > The spikes on the 5V caused the controller chip to malfunction
> > and lock up.
> >
> > Probe around with a digital storage scope to see what happens
> > on power up.
>
> I neither own nor have access to any kind of scope.
>
>
I have seen descriptions of replacing the CFL backlights with white LED strips. That would make a nice project.
Mark
Ian Field
Oct 22, 2015, 5:14:39 PM10/22/15
to
"Percival P. Cassidy" <Nob...@NotMyISP.net> wrote in message
news:d8psur...@mid.individual.net...
> This is a SyncMaster 2233SW that worked fine for years, but then the image
> disappeared. Further investigation showed that the image would display for
> just a second or so after power-up or after switching inputs. So: looks
> like classic defective-power-supply problem, probably resulting from
> crappy electrolytic capacitors.
>
> When I took it apart I found that there were bulging caps and a partially
> discolored PC board.
>
> Since the PC board itself showed signs of overheating, I thought it better
> to look for a replacement power-supply module
Sadly - heat discoloured PCBs isn't as rare as it ought to be.
> disappeared. Further investigation showed that the image would display for
> just a second or so after power-up or after switching inputs. So: looks
> like classic defective-power-supply problem, probably resulting from
> crappy electrolytic capacitors.
>
> When I took it apart I found that there were bulging caps and a partially
> discolored PC board.
>
> Since the PC board itself showed signs of overheating, I thought it better
> to look for a replacement power-supply module
The trick is to make a judgment as to whether there is potentially a fire
risk. In any case - a replacement from the original source will probably go
the same way.
If the problem is on the CCFL inverter board - a company called HR in Spain
does pattern spares.
They were originally well known for high quality pattern replacement
horizontal output transformers for CRT displays.
Percival P. Cassidy
Oct 22, 2015, 6:05:38 PM10/22/15
to
have a replacement for our own use but would rather keep it as a spare
or donate a working monitor to the thrift store/charity shop (whichever
term you use where you live) than simply trash it.
Perce
stra...@yahoo.com
Oct 24, 2015, 2:18:58 PM10/24/15
to
On Thursday, October 22, 2015 at 3:05:38 PM UTC-7, Percival P. Cassidy wrote:
<snip>
The monitors I did this to are in rack mount drawers with keyboard and track pad so the time was worth it to salvage these expensive units. For home use that's your call and with 24" units on sale for $100 it may not be worth the time unless you want the 'education'.
G²
<snip>
> I don't want to put much more money or time into this project: I already
> have a replacement for our own use but would rather keep it as a spare
> or donate a working monitor to the thrift store/charity shop (whichever
> term you use where you live) than simply trash it.
>
> Perce
Older LCD monitors use CCFL (Cold Cathode Fluorescent Lamps) for backlighting and these wear out like any other lamp. Capacitors also go bad FREQUENTLY. There are 'kits' ($15 to $20) to convert CCFL to LED backlighting and I have successfully converted several monitors to LED but it requires above average knowledge. The panel gets disassembled down to individual layers in the backlighting, possible mechanical mods to accommodate the new power module and getting the 12-30 Volt power source into the new power module.
> have a replacement for our own use but would rather keep it as a spare
> or donate a working monitor to the thrift store/charity shop (whichever
> term you use where you live) than simply trash it.
>
> Perce
The monitors I did this to are in rack mount drawers with keyboard and track pad so the time was worth it to salvage these expensive units. For home use that's your call and with 24" units on sale for $100 it may not be worth the time unless you want the 'education'.
G²
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