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AOC 5E monitor with very dark image.

Hello everybody. I'm her to ask you about a problem i can figure out. I have an AOC Model 5E monitor, it turns on, High voltage is there, and scan (raster) works, but the image it displays is so dark that it almost can be viewed. If i push up the screen pot in flyback, the background brightness goes up, but dhe image dont get better, even when retrace lines appears, so is no a flyback fault. It looks more like an video amplitude problem, but i'm not shure. The brightness and contrast controls work fine, but is like the overall values of video amplitude are too low.I`v read a lot about it, and now i'm onfused.I checked de ABL, and adjusting it=B4s level it gets better, but no enough. I got an diagram from eserviceinfo.com, bt it's no accurate (there are entire changed stages),but it=B4s pretty close. However, the voltages i measure are few different from the showed there, and i have no means to know if it is a design difference or an anomaly. Now i show the values i get from the tube terminals, all taken with an ancient digital FLUKE multimeter, in DC Voltage mode:

G =3D 67 V B =3D 68 V R =3D 68 V G1 =3D -27 V G2 =3D 264 V Heater=3D6,07 V

In the video stage it uses LM1279 as driver and LM2438 as power output. The supply voltages for this one look normal (15 and 75 V) I don=B4t know what else can i explain.

Besides, i got an similar problem with an Hurricane Systems Model MT-14SV28NI, but it show intermitent. This one uses the LM1203N and LM2406T pair.

This has become an mistery for me, any help or advice will be welcome. I'm thinking about change the video output ICs, but first i better look here for some answer.

Well, giving thanks from now, i say goodbye.

JCVH - ERDM

Reply to
El.Robot.de.Mimbre
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G = 67 V B = 68 V R = 68 V G1 = -27 V G2 = 264 V Heater=6,07 V

In the video stage it uses LM1279 as driver and LM2438 as power output. The supply voltages for this one look normal (15 and 75 V) I don´t know what else can i explain.

Besides, i got an similar problem with an Hurricane Systems Model MT-14SV28NI, but it show intermitent. This one uses the LM1203N and LM2406T pair.

This has become an mistery for me, any help or advice will be welcome. I'm thinking about change the video output ICs, but first i better look here for some answer.

Well, giving thanks from now, i say goodbye.

JCVH - ERDM

Not familiar with the model, so it's difficult to be precise. However, your G2 voltage seems a bit low - so I would guess that the problem is around there. On some flyback transformers there is a pot to adjust this, and this may need a bit of a tweak. Often there are two pots - one for the focus and one for the A2 (anode 2) - you won't harm anything by adjusting these, except perhaps yourself so be careful what you touch. If it won't adjust up it may be that a high value resistor supplying the anode has gone high, or even open.

Reply to
Barney

" snipped-for-privacy@gmail.com" bravely wrote to "All" (15 Sep 05 15:23:31) --- on the heady topic of "AOC 5E monitor with very dark image."

Check the video processor IC's supply voltage. I've seen the same dark image symptom before where the video IC supply rectifier had gone high resistance because the filter electro had been installed with reverse polarity at the factory.

A*s*i*m*o*v

El> From: snipped-for-privacy@gmail.com El> Xref: core-easynews sci.electronics.repair:342222

El> Hello everybody. I'm her to ask you about a problem i can figure out. El> I have an AOC Model 5E monitor, it turns on, High voltage is there, and El> scan (raster) works, but the image it displays is so dark that it El> almost can be viewed. If i push up the screen pot in flyback, the El> background brightness goes up, but dhe image dont get better, even El> when retrace lines appears, so is no a flyback fault. It looks more El> like an video amplitude problem, but i'm not shure. The brightness and El> contrast controls work fine, but is like the overall values of video El> amplitude are too low.I`v read a lot about it, and now i'm onfused.I El> checked de ABL, and adjusting it4s level it gets better, but no enough. El> I got an diagram from eserviceinfo.com, bt it's no accurate (there are El> entire changed stages),but it4s pretty close. However, the voltages i El> measure are few different from the showed there, and i have no means to El> know if it is a design difference or an anomaly. Now i show the values El> i get from the tube terminals, all taken with an ancient digital FLUKE El> multimeter, in DC Voltage mode:

El> G =3d 67 V El> B =3d 68 V El> R =3d 68 V El> G1 =3d -27 V El> G2 =3d 264 V El> Heater=3d6,07 V

El> In the video stage it uses LM1279 as driver and LM2438 as power El> output. The supply voltages for this one look normal (15 and 75 V) El> I don4t know what else can i explain.

El> Besides, i got an similar problem with an Hurricane Systems Model El> MT-14SV28NI, but it show intermitent. This one uses the LM1203N and El> LM2406T pair.

El> This has become an mistery for me, any help or advice will be welcome. El> I'm thinking about change the video output ICs, but first i better El> look here for some answer.

El> Well, giving thanks from now, i say goodbye.

El> JCVH - ERDM

... If plugging it in doesn't help, turn it on.

Reply to
Asimov

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