Received a Samsung UN32EH4003FXZA LED TV with starting problems. From experience with this model guessed it had bad cap(s) so checked the Power Supply and found the 47uF 160 V cap starting to bulge. The adjacent 47 200 V cap and all the other caps are OK.
To date, the best video I have found for this model TV problem is by radiotvphononut
I would like to upgrade this failed 47uF 160 V cap so would appreciate any suggestions.
Thanks
Ken
erience with this model guessed it had bad cap(s) so checked the Power Supp ly and found the 47uF 160 V cap starting to bulge. The adjacent 47 200 V ca p and all the other caps are OK.
otvphononut
y suggestions.
Look for caps rated to 100 C. This greatly enhances longevity. Raise the capacitance to the maximum that will fit in the space available, up to double OEM. Bring up the voltage to up to double OEM. Look for a decent brand - but if you follow the above, boutique caps are em phatically not necessary.
Peter Wieck Melrose Park, PA
Some caution though: raising capacitance also raises peak current through rectifiers. Rectifiers do have peak current limits.
Cheers!
Hence the "Up to double the OEM limits".
Generally, and unless the OEM is _REALLY_ cheap, the rectifiers are not the limiting factor.
Peter Wieck Melrose Park, PA
** That idea is a common myth about line frequency PSUs and a nonsense about SMPSs.
Doubling the microfarads means the voltage drop is halved during the non conducting period - so when the diode conducts, it has to raise the voltage by half the previous amount. Doing this requires the same current to flow for the same time as before.
The peak current value depends on the transformer's winding resistances and any series inductance.
Increasing the capacitance does increase the start up surge current - but most diodes have large single cycle ratings. The 1N4004 has a 1amp average current rating with a * 30amp * single cycle rating.
.... Phil
If it cycles like the one in the video, it could be that cap. It could also be the main board as Samsungs are notorious for having main board issues ( including cycling). If it starts and has back light shut down but the TV d oesn't cycle, it's most likely a flakey LED in the display. My notes show I did several of these and none of them had a power supply problem.
erience with this model guessed it had bad cap(s) so checked the Power Supp ly and found the 47uF 160 V cap starting to bulge. The adjacent 47 200 V ca p and all the other caps are OK.
otvphononut
y suggestions.
Thanks everyone for your comments!
ohg... "If it cycles like the one in the video, it could be that cap." Yes it does. Is there some way I can post a JPG of bad cap?
pf... "Look for caps rated to 100 C. This greatly enhances longevity." Th e original bad SAMWHA was listed as 105 C.
"Look for a decent brand" Was thinking of using a NICHICON. Any comments?
Checked the cat
Any suggestions concerning Series? Was thinking of upgrading from 160 V t o 200 V? Any comments?
Am unsure if should keep original 47uF or ~ double it?
Are there any references as to difference it will make in cap life?
Am also wondering about normal vs low ESR cap?
Rechecked SAMWHA WL Series
From checking seems SAMWHA has a poor reputation either that or Samsung did a poor job in designing this Power Supply!
It is a BN44-00554B Did a search and lowest price is $14.99 from
If you search "BN44-00554B problems" will find Samsung UN32EH4003FXZA - tri es to start - problem found!
xperience with this model guessed it had bad cap(s) so checked the Power Su pply and found the 47uF 160 V cap starting to bulge. The adjacent 47 200 V cap and all the other caps are OK.
diotvphononut
any suggestions.
s it does. Is there some way I can post a JPG of bad cap?
The original bad SAMWHA was listed as 105 C.
s?
.html
to 200 V? Any comments?
f2/WL.pdf and failed cap was listed as Operating temperature range of 40 ~ +105 C, Extremely low impedance at high frequency, High reliability withst anding 5000 hours load life at 105 C
id a poor job in designing this Power Supply!
ries to start - problem found!
Don't overthink this. This is simply a bridge bypass cap, not a PFC filter . For less than $4 you get two delivered:
Unlikely you'll ever change this cap again.
ohg,
"Don't overthink this. This is simply a bridge bypass cap, not a PFC filter."
Am trying to use this as a learning experience.
I have a hard time believing that Samsung would continue to use poor quality caps in their LED TVs.
Instead am wondering if the Samsung BN44-00554B is a poor design? If this is correct then the 47uF 160 V 105 C cap should be upgraded. My problem is I have No knowledge or experience in this area, which is why am asking for suggestions.
Do you know if the schematic is available on line?
Thanks again for your help!
Samsung will use those caps that are most likely to survive the warranty period by sufficient a margin that the owner forgets when the item was purchased - about 2 years, or so. After which it is counter-productive to improve results.
If the OEM spec. is 47 @ 160 @ 105, stick with the 105, or look for 125C caps. You would do OK with these:
Peter Wieck Melrose Park, PA
A good point that I've seen Phil harping away on in the past; maybe someday folks will get the picture.
I've seen the same error stated in ~40 year old textbooks...
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ity caps in their LED TVs.
Oh please. Manufacturers will use the cheapest part they believe they can get away with, and Samsung is just as bad as anyone else. But more than th at, this was most likely a bad run of caps, not just a crappy selection. I f you replace this with the cheapest one you can find of the same value and voltage I promise you it will last a lot longer than your OEM cap did.
And if you really want to pick on Samsung, their LED TVs are killing LEDs i n the display in wholesale numbers. The last one we did had only 11 out of 44 still working (after I jumped out the open one that caused the shutdown ). 32 LEDs shorted and one open after 2 years of service. THAT is crappy design and/or part selection.
There's no "design" issue involved with your particular failure. It's a si mple full wave bridge and bypass filter. If you want to say the cap was ch eaply spec'd out, that's fair although I still believe it was just a shitty run of caps.
problem is I have No knowledge or experience in this area, which is why am asking for suggestions.
If it makes you feel better, put in a 68uf/250v/105C and get it from Panaso nic.
Not sure, but it probably isn't. Most service manuals these days give you block diagrams and parts lists but not much else. It's often easier to jus t get the datasheets of the ICs in the circuit and work with those than was te time looking for schematics.
I understand that one can calculate inrush current easily; divide input voltage by ESR of the capacitor. So a 220ufd cap (rated at 25V or less -
0.4R ESR) run at 12V will have an inrush current of 12/0.4 = 30A... However a capacitor rated at 35V may have an ESR of 0.2R (60A) and at 63V the ESR may be down to 0.15R (80A @ 12V)Or am I doing something wrong here...
John :-#)#
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** When you simply connect an electro to a DC source, your calc gives the peak surge value.
However, line frequency and SMPSs are way more complicated and the latter usually include a "soft" start systems for the input AC and DC output sides.
.... Phil
ohg,
"Samsung, their LED TVs are killing LEDs in the display in wholesale number s. The last one we did had only 11 out of 44 still working (after I jumped out the open one that caused the shutdown). 32 LEDs shorted and one open after 2 years of service. THAT is crappy design and/or part selection."
Have not checked the display LEDs yet. Could bad LEDs have caused the 47uF cap to fail?
If yes seems like necessary to protect the display LEDs.
Did see mention about turning down the display level.
Hi Phil,
My point was one has to be careful with what cap you choose to replace the original. Too low an ESR may over stress the diodes. If the input is protected with a varistor or similar then indeed, I agree there isn't a problem, however if the bridge rectifier is directly connected to line (via xformer, etc.) then wouldn't lower ESR caps introduce a problem?
John :-#)#
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(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
ers. The last one we did had only 11 out of 44 still working (after I jump ed out the open one that caused the shutdown). 32 LEDs shorted and one ope n after 2 years of service. THAT is crappy design and/or part selection."
F cap to fail?
NO! NO! NO! You're overthinking this again!!
It's simply a rectified and filtered AC supply. They've been building powe r supplies this way since the 1920s. It's simple and foolproof. Your rectif ier is good, your cap is bad. The only external factor that could have caus ed your cap to fail is a weak or open neutral in your house's wiring that d oubled the input voltage. But if that happened, you would notice other thin gs, like light bulbs exploding..
Again, the cap in your TV was likely just a bad run of caps at least, and a poorly spec'd cap at most. Nothing caused it to fail, nor will the failed cap damage any LEDs. Further, shorted LEDs won't harm your AC bridge capa citor.
On a totally different subject, YES, lowering the back light in the menu (p articularly in LED TVs) will extend the life of the back light exponentiall y. When I repair LED TVs for failed back lights, I always modify the LED d rive circuit so that the LED array runs between 30 and 40 percent lower in wattage regardless of where the customer sets it or if it defaults back to full brightness. Customers don't notice and I don't have to worry about th em coming back in warranty.
** In the example given, the winding resistances of the switching tranny are gonna be way higher than the electro's ESR, overriding any effect changes in that value could cause.
Also, actual ESR is not clear from the published data as makers typically quote maximums at room temp. New caps may be half or less that value and in any case ESR drops with rising temp - by a factor of FIVE times more of the temp rises to 100C.
** AC side thermistors or resistors help with inrush surges, but then normally have very little effect afterwards.For practical purposes, the average value of the rectified current is all that matters, which does not change with C or ESR value.
Of course, the diode must be fast enough to handle the switching speeds with low loss.
.... Phil
ohg,
"There's no "design" issue involved with your particular failure. It's a simple full wave bridge and bypass filter."
Thank you for the clarification.
Since this is an inexpensive TV do not want to over do things so the Panasonic is not cost effective.
You have way more experience than I do so when you say "the cap in your TV was likely just a bad run of caps at least..." I believe you!
Am thinking about using a Nichicon replacement and have not found any problems with this brand.
Any experience with them? and last is it even cost effective to upgrade any aspect of original 47uF 160V 105C cap?
Thanks again for your comments!
simple full wave bridge and bypass filter."
sonic is not cost effective.
V was likely just a bad run of caps at least..." I believe you!
blems with this brand.
ny aspect of original 47uF 160V 105C cap?
Cost effective? Ken, the cost to ship a capacitor of this type will far exc eed it's cost.. If you're buying a few hundred thousand of them, then penn ies matter. The cheapest Nichicon 47/160 radial I could find at Digikey th at was in stock and could be purchased one at a time is 0.61c each. The ch eapest Panasonic is 0.71c.
A 68/200v 105 Panasonic with 10K hour life is $1.14
In any case, you're going to have to pay shipping. Does the cost of the ca p actually matter?
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