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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Dell Ultrascan P780 ghosts and fades?
I ran across a Dell Ultrascan P780 a few days ago. Flat CRT, made 1999. When
you first turn it on, lines on the screen (like window borders) ghost very slightly. After about 3 minutes it fades to black over a few seconds. Don't know about the ghosting, but thr fading out sounded like a loose joint going to the tube heater. I prodded around for a while with an insulated probe but couldn't jar anything into working again. What's the likely problem? Are the two defects related? Could the heating element be bad or is there something other than a bad solder joint that could cause it? Thanks GTO(John) |
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Dell Ultrascan P780 ghosts and fades?
GTO(John):
I just repaired one of these P780 a few days ago. It had real strong ghosting next to all the characters on the screen. I had an old junked chassis that had high-voltage problems. I took the CRT neck board from the junked one and put it one the one with the ghosting problem. Perfect picture. Most of the time, the ghosting problems are caused by bad capacitors on the neck board. Either the internal resistance (ESR) of the capacitors goes up in value reducing the action of the capacitor, or the capactance itself goes down. If you have no way of checking the capacitors, I would just replace all of them. There are not that many on this board. Especially replace the one near the video amp IC (the IC with the little heat sink on top of it). Hope this helps... John |
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