Norwood LCD monitor problem

[Steve Kraus]

I have a Norwood 17" LCD monitor. Lately it's been having this problem:

When it has been turned off for a length of time when I turn it on the it
doesn't come on and the indicator LCD flickers somewhat randomly. If I
unplug the VGA video cable sometimes it seems to help and stops flickering
in which case another press turns it on solid yellow and reconnecting the
cable turns the monitor on. Or sometimes another push will turn the
monitor on and it gives the no signal indication and it will be ok when the
video cable is reconnected.

However sometimes nothing works and I have to wait a few minutes for it to
stop flickering. During the flickering period the screen remains off and
no amount of pushing or pushing and holding any buttons help. When the
monitor does come on it's perfectl normal and there's no flicker or any
apparent issues with the cold cathode bulb. (But that doesn't mean there
couldn't be some issue with trying to start it.) Thus far it always
eventually comes on.

I tried running the monitor off a different 12 VDC source but that made no
difference. This is a cheap monitor and it's not the end of the world but
since it works perfectly when it does come on it seems a shame to have to
junk it. I guess I can open it and see if there's anything obvious
(doubtful) or if there are any capacitors back there that could be showing
premature aging from heat vs. lowest quality grade and replace them on
speculation.

Any ideas?

 

[William R. Walsh]

Hi!

Well, it sounds like a no-name monitor to me. That may or may not be a bad
thing.

After reading your description of the behavior, I think it's quite possible
that the power supply is faulty. Disconnecting the computer signal cable
would cause the monitor to power on only enough circuitry to display an LED,
typically an amber colored one. The backlight and panel usually remain off.
(Some monitors do display a "check signal cable" message, however.)

Now, startup is of course the hardest time for any supply, and one that's
marginal could be shutting down and repetitively starting over. If you
reduce the startup load, though, the supply might make it up and stay
running...at least for a while.

I would definitely advise you to look long and hard at the capacitors in the
power supply. They could be cheap, bad or even both. You should also look at
the backlight inverter board.

If by some chance it has an external power adapter, replacement with another
that is known to output the correct voltage and needed current could solve
the problem.

William

 

[Steve Kraus]

Unfortunately I already tried using an alternate supply to substitute for
the brick and no dice. It does seem like maybe there's some problem
getting the bulb started although I don't see any flashings nor issues
once it's on. I guess my next step is to open it up and if see if I can
disconnect the bulb if that makes the rest of the electronics start
normally. Then look for any tired caps in the monitor itself.

Yes, it's just a cheapo that I actually bought intending it for another
use but when I substituted it at home for a CRT "just for testing" even
though the CRT was a nice one I was immediately hooked and there was no
going back. LOL


William R. Walsh wrote:

Hi!

Well, it sounds like a no-name monitor to me. That may or may not be a
bad thing.

After reading your description of the behavior, I think it's quite
possible that the power supply is faulty. Disconnecting the computer
signal cable would cause the monitor to power on only enough circuitry
to display an LED, typically an amber colored one. The backlight and
panel usually remain off. (Some monitors do display a "check signal
cable" message, however.)

Now, startup is of course the hardest time for any supply, and one
that's marginal could be shutting down and repetitively starting over.
If you reduce the startup load, though, the supply might make it up
and stay running...at least for a while.

I would definitely advise you to look long and hard at the capacitors
in the power supply. They could be cheap, bad or even both. You should
also look at the backlight inverter board.

If by some chance it has an external power adapter, replacement with
another that is known to output the correct voltage and needed current
could solve the problem.

William

 

[William R. Walsh]

Hi!

Unfortunately I already tried using an alternate supply to
substitute for the brick and no dice.

I didn't really think this would bring any improvement. It never hurts
to try and now you have confirmed that the trouble is in the monitor.

 It does seem like maybe there's some problem getting the bulb
started although I don't see any flashings nor issues
once it's on.

That's symptomatic of a faulty backlight inverter. Startup is the
hardest time for it.

 I guess my next step is to open it up and if see if I can
disconnect the bulb if that makes the rest of the electronics
start normally.

Be careful! The inverter and its supporting electronics may assume
that the bulb is always present and may not take kindly to operating
without the bulb attached. Something could blow up.

 Then look for any tired caps in the monitor itself.

I would not be surprised if you found some.

Yes, it's just a cheapo that I actually bought intending it for
another use but when I substituted it at home for a CRT "just
for testing" even though the CRT was a nice one I was immediately
hooked and there was no going back.  LOL

I've been down that road, although I only have three flat panels right
now. One is a Gateway that while nice in its day (2000), does not
really compare to the panels of today very well. I also have an Acer
X163W that is the *strangest* panel I've ever seen--it's a 15" 16:9
panel. Still it works well and fits in places where other panels
won't. It's just that the resolution of the panel is a bit strange.

By far and away the best flat panel I have is a 15" Samsung
Syncmaster. It was an eBay find that had been very gently used before
its owner passed away. Even though it is small, I find myself using
the computer attached to it more often than I do my fancy computer
with the 19" ViewSonic CRT!

William

 

[George Jetson]

"Steve Kraus" <screen@SPAMBLOCKfilmteknik.com> wrote in message
news:tumdnWRp3MtambDXnZ2dnUVZ_vednZ2d@earthlink.com...

Unfortunately I already tried using an alternate supply to substitute for
the brick and no dice. It does seem like maybe there's some problem
getting the bulb started although I don't see any flashings nor issues
once it's on. I guess my next step is to open it up and if see if I can
disconnect the bulb if that makes the rest of the electronics start
normally. Then look for any tired caps in the monitor itself.

Yes, it's just a cheapo that I actually bought intending it for another
use but when I substituted it at home for a CRT "just for testing" even
though the CRT was a nice one I was immediately hooked and there was no
going back. LOL


William R. Walsh wrote:

Hi!

Well, it sounds like a no-name monitor to me. That may or may not be a
bad thing.

After reading your description of the behavior, I think it's quite
possible that the power supply is faulty. Disconnecting the computer
signal cable would cause the monitor to power on only enough circuitry
to display an LED, typically an amber colored one. The backlight and
panel usually remain off. (Some monitors do display a "check signal
cable" message, however.)

Now, startup is of course the hardest time for any supply, and one
that's marginal could be shutting down and repetitively starting over.
If you reduce the startup load, though, the supply might make it up
and stay running...at least for a while.

I would definitely advise you to look long and hard at the capacitors
in the power supply. They could be cheap, bad or even both. You should
also look at the backlight inverter board.

If by some chance it has an external power adapter, replacement with
another that is known to output the correct voltage and needed current
could solve the problem.

William

I'm seeing bad caps on the inverter boards lately. Look around the final
transformer for the bulbs there are some electrolytics on the input side and
high voltage on the output side. Some of the better control/feedback chips
will shutdown of the load isn't right.