Magnavox 42MF521D/37B

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  • retiredcaps
    Badcaps Legend
    • Apr 2010
    • 9271
    #21
    Re: Magnavox 42MF521D/37B

    Find the datasheet for 7061 (likey your SMPS IC). Find which pin is VCC. See if the VCC has continuity to the positive leg of the capacitor. If yes, that is the startup cap.

    OR measure the the DC voltage of SMPS IC VCC with respect to SMPC IC GND. Then measure the DC voltage across the cap that you think is the startup. Both DC voltages should be identical.
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      • junktv
        Badcaps Legend
        • Nov 2010
        • 3065
        • USA
        #22
        Re: Magnavox 42MF521D/37B

        Looks like pin 1 is VCC for a TEA1507P. So it's the 100uf 25v cap.

        Haven't said it yet but thanks to you guys taking time out of your day to help others.

          Comment

          • retiredcaps
            Badcaps Legend
            • Apr 2010
            • 9271
            #23
            Re: Magnavox 42MF521D/37B

            Originally posted by junktv
            Looks like pin 1 is VCC for a TEA1507P. So it's the 100uf 25v cap.
            1) 11V DC is the required for the SMPS to start.

            2) What is the DC voltage across the 100uF 25V cap?

            3) What is the DC voltage of pin 1 (VCC) using pin 2 (GND) for ground?

            4) Are any of the voltages fluctuating?
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              • junktv
                Badcaps Legend
                • Nov 2010
                • 3065
                • USA
                #24
                Re: Magnavox 42MF521D/37B

                Both bounce from 1.4-11.

                  Comment

                  • retiredcaps
                    Badcaps Legend
                    • Apr 2010
                    • 9271
                    #25
                    Re: Magnavox 42MF521D/37B

                    Originally posted by junktv
                    Both bounce from 1.4-11.
                    Replace the cap first as it is the easiest and retest/remeasure. Use something like Panasonic FC.

                    http://www.digikey.com/product-detai...0269-ND/266278
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                      • junktv
                        Badcaps Legend
                        • Nov 2010
                        • 3065
                        • USA
                        #26
                        Re: Magnavox 42MF521D/37B

                        Since I have to order them I figure I might aswell replace the rest while i'm at it.

                        3 P10269-ND 100UF 25V FC
                        1 P11232-ND 47UF 35V FC

                        There isn't an FC in 6.8uf 50v but there is a KG P936-ND and GA P14509-ND. I guess KG seems like it would be best since the GA has 5ma less ripple than the original capxon KM.
                        The 2.2 NP is a bi-polar with 25 ripple. It looks like digikey only has a nichicon VP UVP1H2R2MDD-ND instock with that spec or a panasonic SU P1197-ND with only a 18ma rating.

                        See anything wrong with using the P936-ND and UVP1H2R2MDD-ND?

                        Any other parts i should grab just in case while i'm at it?
                        Last edited by junktv; 06-04-2012, 02:55 PM.

                          Comment

                          • TechShui
                            Senior Member
                            • Jun 2011
                            • 148
                            • USA
                            #27
                            Re: Magnavox 42MF521D/37B

                            Have you checked the scaler board yet?

                            I've worked on Magnavox LCD TVs where BOTH the power and scaler boards were bad.

                            Specifically, the caps on the power board are a very common problem, and the IC that generates 12V on the scaler will sometimes blow, leaving a pinhead-sized hole on it.

                              Comment

                              • junktv
                                Badcaps Legend
                                • Nov 2010
                                • 3065
                                • USA
                                #28
                                Re: Magnavox 42MF521D/37B

                                I replaced the cap and i'm getting the same readings.

                                  Comment

                                  • retiredcaps
                                    Badcaps Legend
                                    • Apr 2010
                                    • 9271
                                    #29
                                    Re: Magnavox 42MF521D/37B

                                    Originally posted by junktv
                                    I replaced the cap and i'm getting the same readings.
                                    That leaves 2 likely possibilites.

                                    1) The SMPS itself is bad. What is the resistance between pin 1 and 2 on the SMPS?

                                    2) There is something shorted on the power board causing the SMPS to fluctuate. Likely candidates for shorts might be diodes 6056, 6055, 6054, the diode above 3081, 6066, and others in that general area.

                                    Use the diode check function to measure each. You should have two readings per diode. One should be between 0.3 and 0.8V and the other should show "out of range".
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                                      • junktv
                                        Badcaps Legend
                                        • Nov 2010
                                        • 3065
                                        • USA
                                        #30
                                        Re: Magnavox 42MF521D/37B

                                        Pins 1-2 does a short count up to about 20 @20k then shows open.

                                        6062 near 3081 is reading 001 both ways in circuit and 520/0 out
                                        6054 599/0
                                        6055 606/0
                                        6056 492/0
                                        6066 516/0

                                          Comment

                                          • retiredcaps
                                            Badcaps Legend
                                            • Apr 2010
                                            • 9271
                                            #31
                                            Re: Magnavox 42MF521D/37B

                                            Originally posted by junktv
                                            Pins 1-2 does a short count up to about 20 @20k then shows open.

                                            6062 near 3081 is reading 001 both ways in circuit and 520/0 out
                                            6054 599/0
                                            6055 606/0
                                            6056 492/0
                                            6066 516/0
                                            The above all look okay.

                                            1) Also test 6059, 6075.

                                            2) See if 6076 and the other 3 pin IC on the same heatsink are shorted. Test pins 1-2, 1-3, and 2-3.

                                            3) See if two ICs mounted on the heatsink above 3081 are shorted.

                                            PS. If the photos are more clear and sharp, I could give the actual numbers.
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                                              • retiredcaps
                                                Badcaps Legend
                                                • Apr 2010
                                                • 9271
                                                #32
                                                Re: Magnavox 42MF521D/37B

                                                Test IC above 5062 for shorts.
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                                                  • retiredcaps
                                                    Badcaps Legend
                                                    • Apr 2010
                                                    • 9271
                                                    #33
                                                    Re: Magnavox 42MF521D/37B

                                                    Another test to try is to disconnect all your boards and see if the startup cap voltage still fluctuates or not.
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                                                      • junktv
                                                        Badcaps Legend
                                                        • Nov 2010
                                                        • 3065
                                                        • USA
                                                        #34
                                                        Re: Magnavox 42MF521D/37B

                                                        6059 is all over the place and climbing but was fine when i pulled it.
                                                        6075 755/0

                                                        Not sure if i should be using diode check so they will be the second set.
                                                        6076
                                                        1-2 climbs & climbs to inf
                                                        1-3 0 & 000
                                                        2-3 climbs & 203
                                                        6071 same sink
                                                        1-2 climbs & climbs to inf
                                                        1-3 0 & 000
                                                        2-3 climbs & 276

                                                        above 3081
                                                        7057
                                                        1-2 open & inf
                                                        1-3 open & 775
                                                        2-3 open & 482
                                                        7062 same sink
                                                        1-2 open & inf
                                                        1-3 open & 659
                                                        2-3 open & 470


                                                        I guess you mean the 2 pin deal on a heat sink labeled 6062 next to the large cap. It reads open and 443/0 with diode check.

                                                        I was testing the board on my kitchen counter not hooked to anything else when reading voltages. Btw i didn't replace the other small caps yet just the start cap/
                                                        Last edited by junktv; 06-16-2012, 11:53 PM.

                                                          Comment

                                                          • retiredcaps
                                                            Badcaps Legend
                                                            • Apr 2010
                                                            • 9271
                                                            #35
                                                            Re: Magnavox 42MF521D/37B

                                                            Originally posted by junktv
                                                            6076
                                                            1-2 climbs & climbs to inf
                                                            1-3 0 & 000
                                                            2-3 climbs & 203
                                                            6071 same sink
                                                            1-2 climbs & climbs to inf
                                                            1-3 0 & 000
                                                            2-3 climbs & 276
                                                            1) Well nothing seems obviously shorted. I believe 6076 and 6071 pins 1-3 are supposed to be 0 and 000 if they are dual diodes.

                                                            2) If they are dual diodes, then test it like pins 1-2 like a regular diode and pins 2-3 like a regular diode. You should have 4 readings.

                                                            I could tell if they were diodes are not if they used pcb designations like D601 and D602 rather than meaningless 4 digit numbers.

                                                            3) If you have tested all the diodes and there are no shorts, then you could try replacing the other caps or try replacing the SMPS IC.

                                                            4) findchips.com shows no stock for the SMPS IC so you will have to purchase from ebay.

                                                            5) If you buy the SMPS IC from overseas, it is $4.40 total. If you buy from the USA, the cheapest one is $11.60.

                                                            6) There could be something else shorted on the board causing the fluctuation, but the most likely candidates are the diodes.
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                                                              • junktv
                                                                Badcaps Legend
                                                                • Nov 2010
                                                                • 3065
                                                                • USA
                                                                #36
                                                                Re: Magnavox 42MF521D/37B

                                                                The first numbers where 20k ohm and second in diode mode.

                                                                To fill in the info on the chips they are.

                                                                6052 is a STTH8LD6FP voltage rectifier.

                                                                6076 is a STPS40H100CW schottky rectifier.

                                                                6071 is a MBRF10H100CT schottky rectifier.

                                                                7057 is a W26NM60 zener protected mosfet.

                                                                7062 is a W18NK80Z zener protected mosfet.

                                                                Forgot to label 6051 GBU8J bridge rectifier.
                                                                Attached Files
                                                                Last edited by junktv; 06-17-2012, 07:15 PM.

                                                                  Comment

                                                                  • budm
                                                                    Badcaps Legend
                                                                    • Feb 2010
                                                                    • 40746
                                                                    • USA
                                                                    #37
                                                                    Re: Magnavox 42MF521D/37B

                                                                    "3 P10269-ND 100UF 25V FC
                                                                    1 P11232-ND 47UF 35V FC" May be I am wrong, but I see 4 bad caps (3 are grouped together, and one at the bottom right of the picture).
                                                                    Since this board has PFC, what dc voltage do you get at the main DC filter cap when the TV is off and when TV is on?
                                                                    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

                                                                      Comment

                                                                      • retiredcaps
                                                                        Badcaps Legend
                                                                        • Apr 2010
                                                                        • 9271
                                                                        #38
                                                                        Re: Magnavox 42MF521D/37B

                                                                        Originally posted by budm
                                                                        "May be I am wrong, but I see 4 bad caps (3 are grouped together, and one at the bottom right of the picture).
                                                                        He replaced them in post #8 with an updated picture.

                                                                        Since this board has PFC, what dc voltage do you get at the main DC filter cap when the TV is off and when TV is on?
                                                                        Darn, I keep forgetting about the stupid PFC.
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                                                                          • junktv
                                                                            Badcaps Legend
                                                                            • Nov 2010
                                                                            • 3065
                                                                            • USA
                                                                            #39
                                                                            Re: Magnavox 42MF521D/37B

                                                                            Took a break and put the rest of the caps in and it is still fluctuating.

                                                                              Comment

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