polarity of power cord - gateway fpd1520

[zirath]

If it has got any external metal parts such as RCA (phono) connector outers,
BNC connector outers, 'D' connector surround etc, or possibly screws for a
stand, as these often go right through the plastic case, and into the
internal chassis, then try measuring from any such metal to each of the DC
power input connector's terminals in turn, using an ohm meter. Chances are
you'll find a direct connection, and that will be your DC ground ( "-" )
connection. The other will then be the "+". Assuming that it's a 'standard'
co-axial DC connector, on most modern equipment, 'pin' is "+" and side
contact is "-" although that's not cast in stone. Be aware when you are
obtaining a replacement PSU, that the plug is often a slightly abnormal
size, being a little larger than those you typically find on 'general' power
supplies. Also, make sure that you get one well rated for the job, as these
monitors do draw quite a lot of current, and may well surge up close to the
quoted 2.5 amps at startup, as the LCD backlights first fire up before
settling to their run current.

As to whether it would be safe to reverse connect it, I wouldn't like to
say. Some equipment is perfectly well protected against such 'consumer
antics', but it is by no means guaranteed, and if it is not adequately
protected, the result is often an item that's fried beyond repair, for no
other reason than unobtainable power supply devices, as many previous posts
on this subject over the years, will attest ...

Arfa

The ohm meter showed something like a capacitor on the center pin (it
went to 0 and then back towards the center). The side showed no resistance.

The monitor went on briefly and then went black when plugged into the
power. Seems like it's a dud. Not sure if it's worth trying to repair it
or just return it.

 

[Tim]

The ohm meter showed something like a capacitor on the center pin (it
went to 0 and then back towards the center). The side showed no resistance.

The monitor went on briefly and then went black when plugged into the
power. Seems like it's a dud. Not sure if it's worth trying to repair it
or just return it.

Is there no little pic of the connector around where it give the info
about power? Usually there is a universal icon used that indicates
polarity, kinda like a big C around a dot. Most, but not all, coaxial
power connectors have the minus side on the outside, that way if it
touches a grounded side, it will not destroy the adapter. If the adaptor
cannot start the monitor because it is not powerful enough, it will
sometimes just flash the backlight then go off.

- Tim -

 

[zirath]

Is there no little pic of the connector around where it give the info
about power? Usually there is a universal icon used that indicates
polarity, kinda like a big C around a dot. Most, but not all, coaxial
power connectors have the minus side on the outside, that way if it
touches a grounded side, it will not destroy the adapter. If the adaptor
cannot start the monitor because it is not powerful enough, it will
sometimes just flash the backlight then go off.

- Tim -

The adapter symbol shows center + and side -. It is labeled 12vdc 4a.
The monitor is 12vdc 2.5a so the adapter should have enough power.

 

[Arfa Daily]

The adapter symbol shows center + and side -. It is labeled 12vdc 4a. The
monitor is 12vdc 2.5a so the adapter should have enough power.

Before condemning the monitor, I would feel inclined to just try a different
power supply (bearing in mind that the one you are using now is not an
'original'). The reason that I say this is that there can be quite a high
initial pulse of current demand, as the backlights strike, and it just might
be that the power supply sags a little when hit with this, even though it
*says* that it is rated for 4A ...

Arfa

 

[Arfa Daily]

Before condemning the monitor, I would feel inclined to just try a
different power supply (bearing in mind that the one you are using now is
not an 'original'). The reason that I say this is that there can be quite
a high initial pulse of current demand, as the backlights strike, and it
just might be that the power supply sags a little when hit with this, even
though it *says* that it is rated for 4A ...

Arfa

Thinking about it again, were you trying it with a signal going in ? LCD
monitors, like their CRT counterparts in many cases, don't just 'idle' when
there is no signal. They do just like you say - that is power up long enough
to check if they can detect an input signal, and if they can't, go back to
an inert condition.

Arfa

 

[zirath]

Thinking about it again, were you trying it with a signal going in ? LCD
monitors, like their CRT counterparts in many cases, don't just 'idle' when
there is no signal. They do just like you say - that is power up long enough
to check if they can detect an input signal, and if they can't, go back to
an inert condition.

Arfa

I tried it in a few different conditions: with the monitor on 1st and
then the computer - it showed the computer booting for a few seconds and
then went black - then it came on again after the boot was finished for
a few seconds and then went black again; with the computer on and then
the monitor; with the monitor disconnected from the computer (the manual
says it's supposed to bring up a diagnostic screen in this condition but
it didn't). The screen stayed black the whole time in subsequent attempts.

The power led would go from yellow to green when the computer started
booting but the screen stayed black.

I also noticed that the screen was not completely flush in the housing -
like someone had tried to, or did, open it and didn't close it completely.

 

[Arfa Daily]

I tried it in a few different conditions: with the monitor on 1st and then
the computer - it showed the computer booting for a few seconds and then
went black - then it came on again after the boot was finished for a few
seconds and then went black again; with the computer on and then the
monitor; with the monitor disconnected from the computer (the manual says
it's supposed to bring up a diagnostic screen in this condition but it
didn't). The screen stayed black the whole time in subsequent attempts.

The power led would go from yellow to green when the computer started
booting but the screen stayed black.

I also noticed that the screen was not completely flush in the housing -
like someone had tried to, or did, open it and didn't close it completely.

The fact that the light stays green, is a good sign. What you next need to
do, is to shine a strong desklamp or hand flashlamp at the screen at an
angle, after it has gone back to black. If you can then see an image on the
screen, that indicates that the backlamp tubes are not staying alight. This
could well be because either the inverter is faulty, or that a worn tube is
making the inverter shut down. Either is quite a common fault condition.

Arfa

 

[zirath]

The fact that the light stays green, is a good sign. What you next need to
do, is to shine a strong desklamp or hand flashlamp at the screen at an
angle, after it has gone back to black. If you can then see an image on the
screen, that indicates that the backlamp tubes are not staying alight. This
could well be because either the inverter is faulty, or that a worn tube is
making the inverter shut down. Either is quite a common fault condition.

Arfa

I was able to see the image on the screen - but the monitor remained
black the whole time (it didn't go back to black).

 

[zirath]

I was able to see the image on the screen - but the monitor remained
black the whole time (it didn't go back to black).

(I shined a bright light on the monitor at an angle).

 

[Arfa Daily]

(I shined a bright light on the monitor at an angle).

OK. Well that tells us that the whole monitor part is working, and the
failure is in the LCD screen backlighting circuit. It is generally a bit
fiddly, but it is repairable if you are that way inclined. Unless you are
able (or want to) just throw it back where you got it from.

Arfa

 

[zirath]

OK. Well that tells us that the whole monitor part is working, and the
failure is in the LCD screen backlighting circuit. It is generally a bit
fiddly, but it is repairable if you are that way inclined. Unless you are
able (or want to) just throw it back where you got it from.

Arfa

I'm into trying to repair it.

Is there info somewhere on how to do it?

Thanks for your help.

 

[Arfa Daily]

The fact that the light stays green, is a good sign. What you next

I'm into trying to repair it.

Is there info somewhere on how to do it?

Thanks for your help.

If the screen comes apart easily, start by examining the backlight tubes. Be
careful when extracting them as they are quite fragile. If any are badly
blackened at the ends, suspect them. It's hard to test the inverter, without
having known good tubes to connect to it. If you have a 'scope, you can get
a good idea by looking to see if you have waveform at the primaries of each
of the tube high voltage drive transformers. If you do get a momentary burst
that then disappears, this could be because the inverter is detecting a bad
tube, and shutting down. You might see the tubes initially flash up, and you
might see one not do so. You can disconnect the tubes one at a time, and see
if that keeps the inverter running, and if it does, you can cross connect
the tubes to the opposite inverter outputs, to prove the drive electronics.
Inverters and tubes are available from a number of sources. See, for
instance,

http://www.lcdparts.net/ccfl.aspx

http://www.ergpower.com/pdf30/cross.pdf

http://www.ergpower.com/

Arfa

 

[zirath]

If the screen comes apart easily, start by examining the backlight tubes. Be
careful when extracting them as they are quite fragile. If any are badly
blackened at the ends, suspect them. It's hard to test the inverter, without
having known good tubes to connect to it. If you have a 'scope, you can get
a good idea by looking to see if you have waveform at the primaries of each
of the tube high voltage drive transformers. If you do get a momentary burst
that then disappears, this could be because the inverter is detecting a bad
tube, and shutting down. You might see the tubes initially flash up, and you
might see one not do so. You can disconnect the tubes one at a time, and see
if that keeps the inverter running, and if it does, you can cross connect
the tubes to the opposite inverter outputs, to prove the drive electronics.
Inverters and tubes are available from a number of sources. See, for
instance,

http://www.lcdparts.net/ccfl.aspx

http://www.ergpower.com/pdf30/cross.pdf

http://www.ergpower.com/

Arfa

One thing I started wondering about after you were saying it could be a
problem with the adapter--

The picture of the original adapter that came with the monitor says the
plug is supposed to be 6.5mm o.d. 4.4mm i.d. and 9.5mm long. (Thanks to
Michael Terrell - http://www.lcdpayless.com/productpage.php?productId=237).

The measurements of the plug that came with the adapter I got (from
ebay) are : 5.5x2.5 / 9.5mm.

Could this be the problem?

 

[Arfa Daily]

One thing I started wondering about after you were saying it could be a
problem with the adapter--

The picture of the original adapter that came with the monitor says the
plug is supposed to be 6.5mm o.d. 4.4mm i.d. and 9.5mm long. (Thanks to
Michael Terrell -
http://www.lcdpayless.com/productpage.php?productId=237).

The measurements of the plug that came with the adapter I got (from ebay)
are : 5.5x2.5 / 9.5mm.

Could this be the problem?

As long as the plug is 'making' ok to the centre pin, it shouldn't be a
problem. However, the way round that you have described it sounds wrong. If
the original was looking for a plug with an id of 4.4mm, (which is *very*
big for this type of plug) that would suggest that the monitor has a 'thick'
pin, which I'm surprised that your replacement at just 2.5mm, will fit over.
2.5mm is a pretty 'standard' size.

However, if you can see an image with an external light shone at the screen,
that says that the plug *is* making ok, and the whole monitor is working,
less the backlights. So no, I don't think that will be the problem.

Arfa

 

[zirath]

If the screen comes apart easily, start by examining the backlight tubes. Be
careful when extracting them as they are quite fragile. If any are badly
blackened at the ends, suspect them. It's hard to test the inverter, without
having known good tubes to connect to it. If you have a 'scope, you can get
a good idea by looking to see if you have waveform at the primaries of each
of the tube high voltage drive transformers. If you do get a momentary burst
that then disappears, this could be because the inverter is detecting a bad
tube, and shutting down. You might see the tubes initially flash up, and you
might see one not do so. You can disconnect the tubes one at a time, and see
if that keeps the inverter running, and if it does, you can cross connect
the tubes to the opposite inverter outputs, to prove the drive electronics.
Inverters and tubes are available from a number of sources. See, for
instance,

http://www.lcdparts.net/ccfl.aspx

http://www.ergpower.com/pdf30/cross.pdf

http://www.ergpower.com/

Arfa

I was able to disassemble the front and back panels.

Is the inverter the part that has the power button and various setting
buttons? I was able to disconnect this part.

I didn't see the lcd tubes. The lcdparts.net site didn't have this model
of gateway listed and the instructions for getting to the tubes for the
gateway models they had didn't match.

 

[Arfa Daily]

I was able to disassemble the front and back panels.

Is the inverter the part that has the power button and various setting
buttons? I was able to disconnect this part.

I didn't see the lcd tubes. The lcdparts.net site didn't have this model
of gateway listed and the instructions for getting to the tubes for the
gateway models they had didn't match.

The inverter board is usually long and thin, and has a multipin plug going
to somewhere around its middle, and thickish high voltage wires coming out
of each end to go to the backlight tube connections at either side of the
screen. I seem to recall that there are pictures of inverter boards on at
least one of those sites. they all look pretty much alike generally, if not
in detail. Each backlight tube will have two of these high voltage wires at
either end, that will go back to connectors located at the inverter board
ends.

Arfa

 

[neon]

Anytime that there is involved and don't know the polarity just stick a diode in series . That will prevent from damaging the unit. Usualy that is instlaled on expensive units to make it fool proof . one way it will work the other way it will not. simple