Re: Samsung LN40E550
I am FINALLY back home!! Have soldered a new MOSFET to replace shorted one. Also replaced 13 volt regulator. Will give update on set progress....have a bunch of yard work to do.....
stonoguy
Senior Member
Last Activity: 06-16-2017, 01:05 PM
Joined: 01-28-2012
Location: Greer, SC
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Re: Samsung LN40E550
I am still out of town (In-laws medical)...no access to TV......since I am retired, I am the choice for my "services"!
I will return (hopefully) soon! Thanks for the previous help!
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Re: Samsung LN40E550
I know that Digikey nor Mouser do not have MDD3752......The link to Newegg have them. They are from UTSOURCE. This is where I purchased the ones I have now. The description says these components are REFURBISHED.....huh? I never heard of a refurbished transistor!Leave a comment:
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Re: Samsung LN40E550
Yes, I have…the defective part:
Drain to Source= 0 ohms
Source to Gate = 760 ohms
Gate to Drain = 760 ohms
Shorted for sure!
I am assuming that the data sheet is correct: TO-252
Source is the right leg
The Gate is the left leg
The Drain is the tab.
With the defective component out of the circuit,
I found that the connection where the Source
is soldered, reads ~ 3M ohms…..drops to ~ 4K ohms
then increase again…...capacitor influence??Leave a comment:
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Re: Samsung LN40E550
MDD3752
P-Channel Trench MOSFET, -40V, -43A, 17mΩ
Can not find this part stocked anywhere I have looked in the USA...Mouser, Digikey....can get them from China.....replaced this with the same component. What is the significance of the negative v & A? Also, have found MDD3752RH.....What does RH mean? Would it be OK to use one of these? Also, this component is soldered to the circuit side of the module....the underside......TO-252 package.Leave a comment:
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Re: Samsung LN40E550
Pictures forthcoming.......Leave a comment:
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Re: Samsung LN40E550
Have checked and removed from the circuit the same parts that has been shorted previously....the MDD3752, P channel Trench MOSFET. The set goes dead but doesn't blow any fuse......strange.Leave a comment:
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Re: Samsung LN40E550
Well, I thought it was fixed. Secured all the modules and installed the back & stand. Set played for about 30 minutes and 'poof'!....dead set! I haven't done a thing to this set as I am very 'frustrated' (a nice word for an expletive). Looks as if this is a thermal problem??....any suggestions?Leave a comment:
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Re: Samsung LN40E550
I had another unexpected medical emergence (in-law) that called me out of town and away from that HDTV.
I looked at the MOSFET that I had replace and saw that one of the 3 'legs' connects directly to the 5 volt regulator rectifier. I replaced this rectifier and have played this set without any problems since ~ 10AM this morning (no back installed). (4/7). Hopefully this fix will rectify this on/off problem, We'll see! Will let the set play over night and until 10AM on 4/8 and see if any problems arise. Will assemble the set with stand and back and let...Leave a comment:
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Re: Samsung LN40E550
Received the PCB and the set still cuts off then on after playing approx. 5 minutes or so. This is just like previously. Anything else I should check??Leave a comment:
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Re: Samsung LN40E550
I am hoping so, as well!! I guess replacing a PCB is quicker and more cost effective than the time it would take a TV shop tech to troubleshoot and repair a set. Also, it takes little knowledge about electronics to follow a flow chart and then replace a board! $$$$ talks!Leave a comment:
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Re: Samsung LN40E550
OK.......ordered this board.......hope this corrects the on/off problem.......Leave a comment:
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Re: Samsung LN40E550
OK….here is the info:
Greer,SC USA
SAMSUNG #: BN97=06387P (on sticker) _ BN41-01704 (embossed on board)Leave a comment:
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Re: Samsung LN40E550
What reliable repair outfit would y'all recommend when obtaining a board?....exchange price, correct? How exactly would that work?.....Pay full price for board and when the site receives the dud, you receive a refund for the dud exchange?Leave a comment:
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Re: Samsung LN40E550
I measured the PS_ON voltage on the power supply board.Leave a comment:
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Re: Samsung LN40E550
OK.......went out of town unexpectedly...back now, and found when the set goes down (off), the PS_ON goes to zero volts from ~3.4vdc.....you say the main board is defective?Leave a comment:
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Re: Samsung LN40E550
No, but I will ASAP...........Leave a comment:
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Re: Samsung LN40E550
Does this PSon voltage generated on the main board? On the schematic I have, it appears that PSon is coming from Pin 18 on plug CN802. The connector on the board I have has only 14 pins.....The PSon voltage is labeled on the PS board as being on Pin 14....On the main board CN802 the 14 pin connector, would it be on Pin 2 (SW_P), Pin 10 (SW_I) OR Pin 14 (PWM)?Leave a comment:
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Re: Samsung LN40E550
Pin 7 B13V should read 12.9v on 0v off.......Leave a comment:
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Re: Samsung LN40E550
The first voltage is when the set is 'on', the 2nd voltage is with the set 'off'.Leave a comment:
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