Sam don't sung anymore

posted 23 Sep 2012, 07:53 by Colin Bell   [ updated 23 Sep 2012, 07:57 ]
In a break from the normal weekend activities of swearing over various calibration issues with my 3D printer, I was this weekend offered the chance to pull the TV apart instead. My trusty TV is a Samsung LE40A656A (rolls off the tougue nicely doesn't it?) which has performed very well for about 4 years now, and last week started to exhibit the well documented startup issues, whereby it would cycle through it's POST routine endlessly and never actually power up fully.

This problem is caused by Samsung using cheap capacitors on the PSU board in the TV, which bulge and blow eventually. As the TV was already kinda screwed, and well out of warranty I didn't see any harm in breaking it open for a looksie.

Once the 16 case screws are removed and the back panel pulled free, I was surprised to see that both the mainboard and PSU assemblies are not shielded in anyway - cost saving I guess. 

Once I could see the PSU board, the capacitor issue was immediately apparent and I could clearly see the bulging 1000uF caps which where causing the issue.

As it happens, I picked up a bag of miscellaneous caps last time I was in the UK, and thus had a pair of straight replacements in my store. I would have preferred to put higher temperature and voltage rated replacements in, but the spares I had matched the 105c and 25v of the originals. Rather than a long trip to Moscow to pick up more, I decided to go with these.

The PSU board itself is a Hanoi and not Samsung - (more cost savings?) and had some shockingly bad solder joints on it - I ended up re-flowing about 15 connections in addition to replacing the faulty caps. Cheap crap...

Installation of the new caps and re-flowing the dodgy solder joints actually took about 10 minutes - which is about 15 minutes less than it took to disassemble and reassemble the TV!

The new pair of caps in place on the right at the back.

End result is that the TV is back up and running again!