Xtech
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Dec 30, 2010, 8:25 PM
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Hitachi big screen cycles in protection.
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I am working with an Hitachi big screen model 53SBX59B. When plugging in the power cord the unit immediately starts cycling in and out of protection. It does this continuously without pressing the power button. All 8 of the green leds on the main board that indicate voltage except for D939 5 volt and D946 9 volt come on. Both are monitoring the voltage of a 5 pin regulator, but I'm not sure if either of those are supposed to be lit in standby anyway. They all then go out as soon as it goes into protection. It only takes a couple of seconds for this to all happen. Just as the 6 Leds come on it immediately then goes into protection, then they all go off and the cycle repeats. It does this for as long as its left plugged in. While its doing this I can tell it generating high voltage at the anode of the CRTs. Here's some of what Ive done so far. 1 I have checked all fuses (all ok) 2 Checked all electrolytic caps in the power supply for high ESR and value, all check ok. 3 Checked all transistors and diodes in the protection circuit and power supply. The HOT also checked ok. 4 resoldered joints throughout the supply including any ICs. Any help appreciated, thanks.
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