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Re: DPO70804

 

Thanks. The backlight consists of two very small diameter glass tubes about 10 inches long and somewhere around 1/16 inch in diameter. There are two pink wires and one yellow wire coming out of that assembly and going to a plug on a board that appears to be a high-voltage power supply. The power supply board is even labeled "high voltage." I don't think that is an LED backlight. The pc board patterns going from a module on the power supply board are covered with epoxy up to the connector. I cannot figure out a way to measure the voltages out of the connector to the pink and yellow wires without cutting the wires.

Zack

On Tue, Apr 16, 2024 at 1:45?PM dan.meeks222@... via <dan.meeks222=[email protected]> wrote:

That probably uses LED backlighting, and that may have a separate power connector. So look for that¡­

I doubt it¡¯s got the old CCFL backlight, but that would certainly be a separate connector as the voltage is too high to include with signals.

Good luck and keep us posted.

dan

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From: [email protected] <[email protected]> On Behalf Of Zack Widup via
Sent: Tuesday, April 16, 2024 1:42 PM
To: [email protected]
Subject: [TekScopes2] DPO70804

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I have a DPO70804 scope. The display is dark. I have determined that the fluorescent backlight tubes are not lit. I connected an XGA monitor to the XGA socket on the rear, and the XGA monitor displays the scope display and all functions are working correctly.

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I have been trying to determine if the display tubes or the voltage supply for those tubes is bad, or if the problem is elsewhere. The service manual I have for the unit contains no schematics nor any info on a way to test the fluorescent display circuit.

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The power supply board has a 20-pin plug with voltages on the pins. All the voltages are correct as per a drawing in the manual, except for the -5 volt pin (pin 18). That measures 0 volts. But on the drawing, there is an asterisk next to the -5 volt pin, with no explanation I can find anywhere of what the asterisk means. The PS-ON pin measures 0 volts and the PW-OK pin measures +5 volts.

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Can anybody give me any guidance or suggestions?

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Zack
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