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#41 | |
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C2 shows 0.1v and U1 shows 0.2v between Drain pin and each of all other pins. Pressing the BP5 Power on/off button has no effect.. |
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#42 |
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![]() does u1 get power from the resistor?
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#43 | |
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BTW, 100 Ohms is too high for that fusible resistor, but of testing purpose t is OK for now.
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Never stop learning Basic LCD TV and Monitor troubleshooting guides. http://www.badcaps.net/forum/showthr...956#post305956 Voltage Regulator (LDO) testing: http://www.badcaps.net/forum/showthr...999#post300999 Inverter testing using old CFL: http://www.badcaps.net/forum/showthr...er+testing+cfl Tear down pictures : Hit the ">" Show Albums and stories" on the left side http://s807.photobucket.com/user/budm/library/ TV Factory reset codes listing: http://www.badcaps.net/forum/showthread.php?t=24809 |
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#44 | |
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But pressing the power on/off button still no led light.. *Noted on R1 being a 100 ohm resistor, should get a 2W 8-10 ohm replacement? Last edited by beetle1303; 10-27-2020 at 08:24 PM.. |
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#45 | |
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So the 24V buck converter is working now, now we need to trace out the other power supply section for low Voltage that is used for running those IC's (U3, U4) next. So look up the part number of some of those IC's so you can look up the spec sheet to locate the VCC pin of the IC then you can find out if the VCC is present or not for the IC's to run. Check Voltage of U2, it looks to be LDO Regulator IC. I also see some bad solder joints, one looks burnt, others you can see ring developing around the joint, so look for ring around the solder joints and resolder them. BTW, that small white connector, what is connected to that connector? Last edited by budm; 10-27-2020 at 09:39 PM.. |
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#46 | |
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I looked up for and these are the 2 ICs: 1) Top, bigger one: PIC16F1933: pin 19 & 20 measure 0.03Vdc 2) Bottom, smaller one: HC595A: pin 8 & 16 measure 0.03Vdc Pressing power button on/off has no effect on the readings. |
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#47 |
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![]() You need to check Voltages of U2 which looks like LDO Regulator IC.
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#48 | |
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I put DMM in Volt mode, put black on common pad, and Red on each lead: Left one reads 23Vdc Middle and Right ones read 0Vdc *left side is bulged.. |
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#49 | |
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Does this mean this LDO is faulty/open? |
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#50 |
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![]() https://www.badcaps.net/forum/attach...9&d=1603871079
It looks like it is blown up when the high Voltage dump occurred. Circuit ground for your probe will be the Negative leg of C2, then test Voltage on each leg of that U2. It looks like the center pin is ground, if that is the case then will not be the same as typical 1117 regulator. You can verify if center pin is connected to circuit ground or not by checking the resistance between C2 negative leg and center pin of U2 to see if it shows <1 Ohm or not. You should also check the resistance of the two outer pins against ground. If you cannot read the print then it will be hard to figure out what the output Voltage should be, it may rated as the same Voltage for the IC's VCC. Last edited by budm; 10-28-2020 at 01:43 PM.. |
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#51 |
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![]() BTW, look real close at C6 and C7 soldering joints connected to U2 pin 1 and pin 3, they do not look right.
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#52 |
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![]() The LDO looks blown up to me. Check C6 & 7 for short and check the capacitance.
Last edited by CapLeaker; 10-28-2020 at 07:25 PM.. |
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#53 | |
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Pin1: 23 Vdc / 146 ohm Pin2: < 1 Vdc / < 1 ohm Pin3: < 1 Vdc / 14 ohm Black probe on Pin2: Red probe on Pin1: 23 Vdc / 152 ohm Pin3: < 1 Vdc / 14 ohm Marking on U2 is completely not readable. *** Just to be clear: Pin1 is on the left and Pin3 is on the right of the picture I attached. Last edited by beetle1303; 10-28-2020 at 10:25 PM.. |
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#54 |
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#55 |
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#56 | |
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I do not understand why your readings show Voltages. Are you checking the resistance of C6 and C7 with POWER applied to the unit while doing resistance test? Last edited by budm; 10-29-2020 at 12:57 AM.. |
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#57 | |
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So my reference of Pin1 & Pin3 is reversed. Based on your picture: Pin3: 23 Vdc / 146 ohm Pin2: < 1 Vdc / < 1 ohm Pin1: < 1 Vdc / 14 ohm Black probe on Pin2: Red probe on Pin3: 23 Vdc / 152 ohm Pin1: < 1 Vdc / 14 ohm |
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#58 | |
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With U2: C6: 178 ohm / 0L on capacitance C7: 14 ohm / 0L on capacitance Without U2: C6: 539 ohm / 103 uF on capacitance C7: 20.8 ohm / 0L on capacitance ** Pin1 resistance now 20.8 ohm vs 14 ohm previously. |
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#59 | |
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#60 |
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![]() I think C7 may be shorted too. Take it out and remeasure it out of circuit.
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