Dell 17" LCD monitor shuts down.
in [Repair]
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From: grobinso on 8 Jan 2007 16:11 David, ok, i havent been able to get any of them over here but i have used BD911 as test devices. If you get a minute would be interested to know what voltage you have on pin9 of the PWM chip as i mentioned in my last post. Graham "David Farber" <farberbear.unspam(a)aol.com> wrote in message news:enua68$n9b$1(a)aioe.org... > >> >> "David Farber" <farberbear.unspam(a)aol.com> wrote in message >> news:enmdu4$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 > >
From: David Farber on 9 Jan 2007 16:15 > > > "David Farber" <farberbear.unspam(a)aol.com> wrote in message > news:enua68$n9b$1(a)aioe.org... > > > >> > >> "David Farber" <farberbear.unspam(a)aol.com> wrote in message > >> news:enmdu4$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 > > > > > > <grobinso(a)lycos.co.uk> wrote in message news:9syoh.13411$696.1764(a)newsfe7-win.ntli.net... > David, ok, i havent been able to get any of them over here but i have used > BD911 as test devices. > > If you get a minute would be interested to know what voltage you have on > pin9 of the PWM chip as i mentioned in my last post. > > Graham Graham, Is it ok that the bad transistors are removed when I check the voltages? I haven't received the replacements yet. -- David Farber David Farber's Service Center L.A., CA
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