Dell 17" LCD monitor shuts down. [Repair]

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From: David Farber on 6 Jan 2007 20:32

"Jim Yanik" <jyanik(a)abuse.gov> wrote in message
news:Xns98AFC7B524E56jyanikkuanet(a)64.209.0.86...
> "David Farber" <farberbear.unspam(a)aol.com> wrote in
> news:enmio3$pso$1(a)aioe.org:
>
> >
> >>>This 17" Dell monitor, model number CN-0M1609-4633-3AG-2DTL, will
> >>>power on when AC is first applied.
> >>> In the middle of the screen appears, "Dell Genesis
> >>>Display Perfection." Then it disappears after a second. When you
> >>>press the power button with no input signal, the Dell self test
> >>>feature check illuminates in the bottom left corner of the display.
> >>>You can see the red, green, blue, and white bars within the self test
> >>>box. Then, it starts to scroll diagonally up to the right for about a
> >>>second and then the display turns off. The power light remains on. If
> >>>you hook it up to a PC, you do
> > not
> >>>get any display. The boards are in good condition and I reflowed the
> > solder
> >>>over many of the components with no improvement.
>
> Why did you reflow solder? Were there bad joints or intermittents?
>
> >>>Any ideas what might
> >>>be going on here?
> >
> > "Simoc" <simoc(a)suomi24.fi> wrote in message
> > news:1168033267.590015.315300(a)51g2000cwl.googlegroups.com...
> >> Bad caps?
> >>
> >> --
> >> Top-posting not supported.
> >>
> >
> > The caps tested ok.
> >
> > Thanks for your reply.
> >
>
> tested how? ESR meter? capacitance meter? ohmmeter?
>
> --
> Jim Yanik
> jyanik
> at
> kua.net

ESR with my Bob Parker, ESR meter and an ohmeter for shorts.

Thanks for your reply.

--
David Farber
David Farber's Service Center
L.A., CA

From: David Farber on 6 Jan 2007 20:40

From: me on 7 Jan 2007 05:29

>> >>>This 17" Dell monitor, model number CN-0M1609-4633-3AG-2DTL, will
>> >>>power on when AC is first applied.
>> >>> In the middle of the screen appears, "Dell Genesis
>> >>>Display Perfection." Then it disappears after a second. When you
>> >>>press the power button with no input signal, the Dell self test
>> >>>feature check illuminates in the bottom left corner of the display.
>> >>>You can see the red, green, blue, and white bars within the self test
>> >>>box. Then, it starts to scroll diagonally up to the right for about a
>> >>>second and then the display turns off. The power light remains on. If
>> >>>you hook it up to a PC, you do
>> > not
>> >>>get any display.

Judging from the described defects in operation there seems to be a problem
in the electronic circuitry. I advise a basic troubleshooting routine be
performed on this device to localize the defective circuitry.

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From: grobinso on 8 Jan 2007 14:34

Hi David

I bought aDell E172fp off Ebay recently which was sold as faulty, the Power
Light would flash on/off with no display.

Basically, what i have found is that the output transistors go s/c, these
are the small 2sc5707 transistors that sit near the 4 yellow transformers. i
had 2 go s/c in one of the channels, the other channel was ok. I replaced
these and now the green light stays on , the display comes on for about 3
seconds like you's does and then goes off.

I put a scope on the o/p of the transformers and can see them switching ok
for 3 secs then the o/p goes off. What is happening is that the Pulse Width
Modulator chip that drives the lamps is shutting down after 3 seconds, this
is the 16 pin chip marked TL1451A. I have the datasheet on this chip and i
am currently trying to work out why it shuts down. I have found that whe
you first switch on the monitor, the supply to this chip is 18vdc, when the
display comes on for 3 seconds this drops to 14 volts (because this supply
is unregulated) and then goes back to 18vdc.

I would be interested to know if you can confirm the dc voltage you are
seeing on pin 9 the 16 pin TL1451A chip during this startup period and
see if it compares to my results.

Theres a common problem here with these monitors, it may be overcurrent due
to s/c transformers or another transistor s/c somewhere, i am sure we will
track it down shortly.

Graham

"David Farber" <farberbear.unspam(a)aol.com> wrote in message
news:enmdu4$e8m$1(a)aioe.org...
> This 17" Dell monitor, model number CN-0M1609-4633-3AG-2DTL, will power
> on
> when AC is first applied. In the middle of the screen appears, "Dell
> Genesis
> Display Perfection." Then it disappears after a second. When you press the
> power button with no input signal, the Dell self test feature check
> illuminates in the bottom left corner of the display. You can see the red,
> green, blue, and white bars within the self test box. Then, it starts to
> scroll diagonally up to the right for about a second and then the display
> turns off. The power light remains on. If you hook it up to a PC, you do
> not
> get any display. The boards are in good condition and I reflowed the
> solder
> over many of the components with no improvement. Any ideas what might be
> going on here?
>
> Thanks for your reply.
> --
> David Farber
> David Farber's Service Center
> L.A., CA
>
>

From: David Farber on 8 Jan 2007 15:39

>
> "David Farber" <farberbear.unspam(a)aol.com> wrote in message
> news:enmdu4$e8m$1(a)aioe.org...
> > This 17" Dell monitor, model number CN-0M1609-4633-3AG-2DTL, will power
> > on
> > when AC is first applied. In the middle of the screen appears, "Dell
> > Genesis
> > Display Perfection." Then it disappears after a second. When you press
the
> > power button with no input signal, the Dell self test feature check
> > illuminates in the bottom left corner of the display. You can see the
red,
> > green, blue, and white bars within the self test box. Then, it starts to
> > scroll diagonally up to the right for about a second and then the
display
> > turns off. The power light remains on. If you hook it up to a PC, you do
> > not
> > get any display. The boards are in good condition and I reflowed the
> > solder
> > over many of the components with no improvement. Any ideas what might be
> > going on here?
> >
> > Thanks for your reply.
> > --
> > David Farber
> > David Farber's Service Center
> > L.A., CA
> >
> >
>

<grobinso(a)lycos.co.uk> wrote in message
news:I0xoh.22673$RL5.14448(a)newsfe2-gui.ntli.net...
>
> Hi David
>
> I bought aDell E172fp off Ebay recently which was sold as faulty, the
Power
> Light would flash on/off with no display.
>
> Basically, what i have found is that the output transistors go s/c, these
> are the small 2sc5707 transistors that sit near the 4 yellow transformers.
i
> had 2 go s/c in one of the channels, the other channel was ok. I replaced
> these and now the green light stays on , the display comes on for about 3
> seconds like you's does and then goes off.
>
> I put a scope on the o/p of the transformers and can see them switching ok
> for 3 secs then the o/p goes off. What is happening is that the Pulse
Width
> Modulator chip that drives the lamps is shutting down after 3 seconds,
this
> is the 16 pin chip marked TL1451A. I have the datasheet on this chip and i
> am currently trying to work out why it shuts down. I have found that whe
> you first switch on the monitor, the supply to this chip is 18vdc, when
the
> display comes on for 3 seconds this drops to 14 volts (because this supply
> is unregulated) and then goes back to 18vdc.
>
> I would be interested to know if you can confirm the dc voltage you are
> seeing on pin 9 the 16 pin TL1451A chip during this startup period and
> see if it compares to my results.
>
> Theres a common problem here with these monitors, it may be overcurrent
due
> to s/c transformers or another transistor s/c somewhere, i am sure we will
> track it down shortly.
>
> Graham
>

Hi Graham,

I checked those 2SC5707 transistors again. This time I found two of them,
Q759 and Q760, were shorted b-e. I'll order those parts, replace them, and
let you know what happens.

Thanks for your reply.

--
David Farber
David Farber's Service Center
L.A., CA

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