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Old 07-26-2010, 01:03 PM   #1
retiredcaps
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Join Date: Apr 2010
City & State: Canada
Posts: 9,065
Default CMV CT-934D won't power on - secondary voltages disappear

CMV CT-934D won't power on - no power LED

SUMMARY
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This is a CMV CT-934D made in 2004 LCD. It won't power on. The power LED does not turn green.

THINGS TESTED
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1) Measured steady 164V DC across main filter capacitor.
2) With the power board ONLY (i.e. logic board is disconnected), the secondary voltages 19V and 5V DC are present at connector location CN100. The 19V and 5V DC voltages are steady and do no fluctuate.
3) Fuse FP1 on logic board reads 0.3 ohms.
4) All connectors from power board connector CN100 to logic board location CN2 read 0.3 ohms. That is, the connectors are fine.

PROBLEM
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1) Press the power button and the power LED does not come on.
2) When the logic board is connected to the power board, the voltages found at CN100 disappear. The 5V DC disappears immediately. The 19V DC drops slowly from 19V to 0V. I can see the voltage dropping on the multimeter. It drops about 1V every 5 or 10 seconds. The voltages at CN2 on the logic board show the exact same behaviour as CN100 (drop and disappear).

QUESTION
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What could cause the secondary voltages to drop/disappear when the logic board is connected to the power board? When the logic card is disconnected, the secondary voltages are solid and steady on the power board.
Attached Images
File Type: jpg logic-back.jpg (255.6 KB, 1745 views)
File Type: jpg logic-front.jpg (523.6 KB, 3222 views)
File Type: jpg overall.jpg (426.2 KB, 1571 views)
File Type: jpg powerboard-back.jpg (384.9 KB, 2838 views)
File Type: jpg powerboard-front.jpg (285.1 KB, 6793 views)
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