This TV was a junker so I'm just trying to learn something about repairing them,knowing that it would be simplier to just replace boards until i get lucky but I'd sort of like to try fixing. The set when powered on the indicator light goes from red to blue I hear a slight click as if to power on(no display)but nothing happens.I did have a dvd player connected to see if there was sound but that wasn't there either.Started checking voltages with my DMM and found 3.3 volts from power button to the connector on the logic board?(main board)this pin is marked 5v I understand that this is the stanby voltage and forever present being only 3.3 is that an issue. When powered on the ps-on pin on the power board gets 4.4v there is 5v's present at the 5v pin of that connector but when measuring for the 12/24v I get no measurements. When checking the l117 regulators at U703 there's 3.3 at the tab (v/out) and 5.2 at (v/in) ofcourse nothing on adjustment legs. U707 in same order shows 1.8 and 3.3 I noticed U709 (v/in) was low like 0.069 this was an adjustable regulator not fixed I replaced it with a 117L hopeing its adjustable it was all i had at the time and now have 2.2 (v/out) 3.3 (v/in) and 1.7 at the adjustment is that okay? Then there are 2 high voltage regulators that have no reading U708 and U710 also on this board there are 3 EMI filters on one i have 5 volts both sides the other 2 read infinite I'm thinking that because no 12/24 volts are present is why there's no current is that the case with U708 and U710? Found out that U708 is a 5a low dropuot linear regulator could that be whats stopping the flow because U710 is behind it and no voltage there? then on the Switch Mode Power Suppy (SMPS) at photocoupler IC952 (PC123) has 63.5v in standby and 62.6 at ps-on but there's no voltage at the collector in standby or ps-on. While IC932 and IC934 on standby side of board shows at the anode 67.9 and 68.7 volts with neg.test lead attached to neg. leg of 450v capacitor and meter set at DC 500 volts.The collectors of these 2 photocouplers IC932 shows 1.5,IC934 shows 15.6 when ps-on is applied the readings change to this on IC932 anode goes to 65.4 and the collector to 2.2 on IC934 the anode switches from the 68.7v to 62.6 and the collector goes from 15.6 to 14.5v. So is it normal for these measurments of the IC's to be like this? To me it seems right but i'm not sure. these are the problems I've noticed with the set and hey any help would be payed forward
have the schematics but can't seem to post it
have the schematics but can't seem to post it
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