Educate me about capacitors....

[slaveofconvention]

I know I'm semi-hijacking this forum but it's the closest I can find :p

I'm about to (attempt to) repair a second Samsung TV with a now notorious clicking and no power issue. I've read a dozen or more pages on how to do it in the past (and managed the repair last time) but it seems more up-to-date information has surfaced since I did the repair.

The main issue is that 5 capacitors (or a couple of the five) fail - bulging top, leaks - you know the deal. The caps are (I believe from memory) 2200uf 10v 105c units. More recent info seems to say that the TV power supply actually pumps 12v through these caps.

Can I use 16v caps instead of the 10's safely - a couple of the sites I've been looking at suggest this should be ok.

What are "better" caps - what should I be looking for to avoid the customer coming back in 6 months with "It isn't working again!!!"

The caps are the two pin solder into a PCB type (if that makes any sense) and the spacing is pretty tight so they need to have the connectors at the same end, not with a connector at each end...

Those of ya willing to put a little time into this, if you can point to specific units on this site - http://www.rswww.com - that'd be ideal as I want this done asap and there's a local trade counter for the company. I just don't have the space to have a 40" LCD tv sitting around for any length of time.

Thanks in advance....

Not entirely sure how the local "computer guy" ended up fixing TV's but it's for my landlord so I'm willing to take the time - he certainly looks out for me whenever he can....

[Oneslowz28]

Ok Lets start at the beginning.

The caps that will be bulging or busted are electrolytic. Meaning they have an electrolyte inside. This is the stuff that oozes out. The bulging or bursting is always caused by the electrolyte breaking down and forming hydrogen. Now that you know why, lets move on.

Electrolytic Capacitors (http://en.wikipedia.org/wiki/Electrolytic_capacitor) are almost always polarized. Meaning that you must take care when installing the new ones not to reverse the polarity. 99% of the smaller electrolytic caps have a stripe on one side. This stripe is always on the same side as the negative lead. If the PCB is not marked use a fine point sharpie to mark the side with the stripe.

Electrolytic Capacitors store energy which is measured in Micro Farads (http://en.wikipedia.org/wiki/Microfarad) (uF). It is important to always use the same uF value when replacing caps.

The second measurement on a cap is the voltage. This is less important than the uF value. It is good practice to replace blown caps with a higher voltage as the Voltage number on the cap is just the maximum voltage that the cap can withstand before breaking down. I always replace and design my circuits with caps at least 3 times the actual voltage they will see. So if the caps that came with the TV are 10V I would replace them with 16 or 24v caps as they most likely the circuit they are filtering is 5v or 9v. I can assure you that any cap you put in will be better than the 10v ones that are in it.

So why does the electrolyte break down if the cap is rated for 10v and its on a lower voltage circuit?

Caps also have a third rating that is important. The Tolerance rating is given in a percentage. Usually 5% 10% 20% and 20-30% Most of the caps you can buy in stores and on anything but the largest suppliers websites are 20% tolerance caps. In theory a 2200uF 10V cap rated at 20% means that it could fail at 20% lower than its specified voltage or it could handle 20% more power than its specified voltage. In reality it means that it can only safely handle voltages up to 8volts. Hence why I recommend going 3 times your max voltage that the cap will be handling.

Give me a second and I will find the caps for ya

[Oneslowz28]

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6841923

or

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6841955

or even better

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6841992

[nevermind1534]

I think I have some extra caps the match your specs left over from when I recapped a computer mobo. Let me know if you need them, and I'll send them your way (It will only cost me $1.23 to send them).

You can always increase the voltage of capacitors (the rated voltage is only a maximum), but you usually want to leave the capacitance alone (especially for electronics), unless you really know what you're doing.

[mDust]

I also have a Samsung TV with bad caps on the power supply board which causes power cycling under certain circumstances. It started for me about 2 months after the warranty expired and Samsung told me it would cost $400 or so for the power board because it's a discontinued model. I think I'll pass on that! If you fix it with new caps then maybe I'll man-up and try it on mine. Make sure to post your success or failure to get it working again.

[slaveofconvention]

I already fixed one - it wasn't a problem - about 25 screws and desolder and resolder 3 caps in that particular TV - the reason for my question is that the last one I fixed was for my boss so I figured, screw it, as long as they work it'll do. This TV is for someone I actually LIKE lol so I wanted to use a higher quality cap if possible to make sure the repair lasts....

CJ - the caps you linked to are all 85c ones - I'm 99% sure the ones I'm replacing are 105's - is that important?

For what it's worth, not really our purview I know, but I'll do a full step-by-step photo tutorial on this as I do it...

[nevermind1534]

Probably any cap that you can buy (not one of those ebay ones from china) will be better than the ones that are in there and will last longer than the TV.

[slaveofconvention]

I'm thinking these will do the job - seem to have all the right numbers, and at 7000 hours mbtf they seem to be about the longest lasting - http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2189767

Or am I missing something blatently obvious?

[crenn]

If the electronics get upto 85c, I'm pretty sure the capacitors won't be the only thing not working.

[Oneslowz28]

If you want to go back with the 105 just make sure you up the voltage to 25 minimum just to have a nice buffer zone to rely on. I don't know about that TV by my 42 and 50 both get very warm to the touch in the back.

[LiTHiUM0XiD3]

did this to a LG recently... the guy told me that they charged him almost $200 for the last repair.. and all the did was replace the PSU.. so about a year later... caps blew again
they were 2200uf 10V.. i swapped em for 25V caps.. (same kinda issue.. it would shut off.. and then not display anything till it had like an hour cool off time)
the guys tv hasnt had even a flicker...