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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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#1
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Acer 77e Black Screen Until Warmed-up
This 17 inch monitor turns on and has HV but the screen is completely black
for about 5 minutes. Gradually, it brigthens up but the images look out of convergence [?] - blurred, colors off, unreadable. After about 30 minutes the picture is superb. OSD works fine. No matter how long the monitor then remains in standby, it comes back perfectly. I'm guessing maybe a failing capacitor in the SMPS and will test with freeze spray. Any better clues/hints/suggestions to limit my hunt would be apprecaited. Thank you. -- Remove -NOSPAM- to contact me. |
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Hi John,
Look for a capacitor in the filment supply of the CRT. You'll probably find one bad causing almost no filament voltage when the monitor is cold and as it (the cap) heats up, the filament voltage slowly increases to 6.3 volts or close. Find the filament terminals on the crt socket on the neck pcb then trace the apropriate wire back to the main PCB and you should find the right capacitor pretty easily. |
#3
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Hi John,
I agree... Many monitors create the heater voltage in the SMPS instead of the flyback. Check the low voltage caps in that area. If you have an isolation transformer, you could check the heater voltage when cold and watch it as the monitor warms up. When working on live equipment, follow the safety guidelines in the repair faq (www.repairfaq.org). Be carefull! Most of the time, the live area will be well marked on the board. Kirk S. "techdrive" wrote in message lkaboutelectronicequipment.com... Hi John, Look for a capacitor in the filment supply of the CRT. You'll probably find one bad causing almost no filament voltage when the monitor is cold and as it (the cap) heats up, the filament voltage slowly increases to 6.3 volts or close. Find the filament terminals on the crt socket on the neck pcb then trace the apropriate wire back to the main PCB and you should find the right capacitor pretty easily. |
#4
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On Sun, 31 Oct 2004 16:52:19 -0500, "techdrive"
wrote: Hi John, Look for a capacitor in the filment supply of the CRT. You'll probably find one bad causing almost no filament voltage when the monitor is cold and as it (the cap) heats up, the filament voltage slowly increases to 6.3 volts or close. Find the filament terminals on the crt socket on the neck pcb then trace the apropriate wire back to the main PCB and you should find the right capacitor pretty easily. Or start at the SMPS and identify the 6.3 VDC source, and replace its filter capacitor. Tom |
#5
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On Sat, 06 Nov 2004 22:41:57 GMT, "Kirk S."
wrote: Hi John, I agree... Many monitors create the heater voltage in the SMPS instead of the flyback. Check the low voltage caps in that area. If you have an isolation transformer, you could check the heater voltage when cold and watch it as the monitor warms up. When working on live equipment, follow the safety guidelines in the repair faq (www.repairfaq.org). Be carefull! Most of the time, the live area will be well marked on the board. Kirk S. Right... I have never seen a PC monitor that derived its filament voltage from the FBT. Tom "techdrive" wrote in message alkaboutelectronicequipment.com... Hi John, Look for a capacitor in the filment supply of the CRT. You'll probably find one bad causing almost no filament voltage when the monitor is cold and as it (the cap) heats up, the filament voltage slowly increases to 6.3 volts or close. Find the filament terminals on the crt socket on the neck pcb then trace the apropriate wire back to the main PCB and you should find the right capacitor pretty easily. |
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