TLDNR; Have an old SAMSUNG TV with blown hybrid MOSFET/controller IC on power board to be replaced; replaced blown main capacitor on same power board several years ago successfully, and TV has been working fine since until this IC popped all of a sudden. Want to know what if anything to check on board to make sure before replacing and testing with new IC. Have 2 new matching ICs, DIP socket to make removal/replacement easier, a whole other known-good power board with which to compare, if necessary.
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Re: what to check before replacing hybrid MOSFET/controller IC on SAMSUNG TV power bo
I have this trusty old 32-in SAMSUNG LCD TV that I'm repairing a second time, and would appreciate some feedback before I pull the trigger on this second round since this time it involves an active component replacement instead of just a cap.
It's a 10+ year old TV, but it has served me well as my office/den TV and is more than sufficient in that role. I've had a few problems with it and it lacks some modern functions, but nothing too troublesome for its age nor anything I can't live without... For example, when powering on, it displays a single vertical green line that goes away after it has warmed up a bit; I'm assuming due to some of the circuit film alongside the LCD having delaminated a bit. Since it makes proper contact when warmed up and expanded, it's no bother. As long as the display lasts, I'm fine fixing things as I go as much as I economically can instead of sinking a bunch of money into a brand new set for where it's used.
Several years ago, the TV stopped turning on and would get stuck in power LED on but no display/power LED off loop with a clicking relay sound. Following suggestions from people with similar experience on YouTube and forums like this one, I suspected a cap on the main power board. I did have SAMSUNG official service take a look at it (if only to observe them open it up properly) and we were able to confirm the largest capacitor on the power board had in fact blown. Of course, SAMSUNG service would not do a component repair and wanted an arm and a leg for a replacement board. No problem; since it was a simple and large size desolder/solder job, I simply ordered a $1 replacement capacitor and a spare to have on hand with the same capacitance and slightly higher voltage rating (as often suggested from what I read/watched) and swapped with the broken one. The TV worked fine after that for quite a while.
Then one day, I assume due to a power surge or something similar, I heard a "pop" turning it on after which the screen went dark and would not let me turn it back on. Suspecting the replacement capacitor having died, too, opened it back up. Surprisingly, the replacement cap and others were fine — no bulging, no leaks, none of them blown, no broken solder traces, etc. Instead, a small 8-pin DIP on the power board appeared to have blown with its top nowhere to be found. Searching by the model number of the power board online, I found photos from which I identified it as an A6159, apparently a MOSFET/controller IC hybrid. I ordered a couple (just in case), along with a 8-pin DIP sockets so as to make future replacements easy should it fail again. I also got hold of a used working full replacement power board as a spare.
Desoldering the popped IC and resoldering a socket in its place and inserting the IC is no problem, of course. What I wanted to ask is, before I go ahead and test it live, is there any voltages/shorts I should check for in case it was not a power surge that blew it, but some other component that failed. I'm attaching a photo of the failed board for review; all the caps look visually OK to me, as do the rest of the components, but I'm not expert on power circuits. Any and all suggestions would be very much welcome!Attached Files -
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Re: what to check before replacing hybrid MOSFET/controller IC on SAMSUNG TV power bo
Incidentally, I didn't know whether to post this here or in the sister "Troubleshooting Power Supplies and Power Supply Design" subforum, but most of the recent threads in the other seem to be PC power supply related and thought it better fit here. I also didn't want to cross-post, but if that's a more appropriate place, I can re-post there or ask a moderator to move it for me. Apologies in advance if I made the wrong choice.
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Re: what to check before replacing hybrid MOSFET/controller IC on SAMSUNG TV power bo
Replace CB803, CB804 and CB806 as well. Check that DB851 is not shorted, and due to the age I might also replace CP811 and CM807.
You can use a 60w incandescent lamp in series with the a/c line input to limit current incase there is a short somewhere.Comment
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