can some one please help me id this capacitor, its an easy one for an expert im sure!

[steptoe1111]

hey guys how is every one
like i said in the title im just trying to id this tantalum capacitor, the markings on it are 684k 450me,
its running in a lcd power supply on the HOT side (a/c)side here is a photo




it looks like theres 2 of them running in paralel ,
can any one sugest a replacement part ?
maybe one jay car or radio shack carry
OR please more importantly tell me what the value of this part is at a guess i think it may be .684uf/450v would i be corect?
ps please forgive my lack of knoledge im self tought with know education
im great with poweramps and can diagnose faulty componants with a scope and multimeter plus ive built nearly every kit jaycar has to offer
but the main reason for this is because i have been given a 50 inch lcd tv
with a faulty power supply and im just haveing a poke around and found this fault wich i dout isent the only one but i can id everything els... any help is greatly apreciated thank you very much and hope everyone has a great day

[metalsculptor]

Just going on the size it would be a 450V part and the value is 0.68uF, the 4 is the decade multiplier 10000 nF x 0.68 in this case

[Elvee]

It is a plastic film cap, probably PP.

Normally quite reliable, and generally fails in a visible manner: cracks, burns, etc.

First check the lytics and power semi's, that's the most likely place for failure.

[steptoe1111]

cheers guys
yeh this one is actualy buzzing i thougt it was an open secondry in the tranny but they all seem fine thanks for that guys
you are all unreal testing all those semiconductors soon once i got some spare
tinker time.. on the board its self there seems to be 4 d/c chanels out im geting 5v out of one, 12v out of the next and 24v out of the 3rd and nothing at all out of the forth ,
so that tells me i think the damage should be localised to a small section of the board, atleast now i can go get a replacement cap or pull another one from some junk in the spare room thanks again everyone you guys are the best
ps i hate power suplys gimme a power amp anyday

[Mooly]

Many SMPS don't run correctly (or as you expect) with no load. Some outputs may be switched or fall to a low value as the unit enters standby. 99% of problems are dried out electroylitics. Buzzing is usually the ferrite components, maybe because the drive is incorrect.

[steptoe1111]

Originally Posted by Elvee

It is a plastic film cap, probably PP.

Normally quite reliable, and generally fails in a visible manner: cracks, burns, etc.

First check the lytics and power semi's, that's the most likely place for failure.

sory mate but can you please tell me what a lytics is? i may posibly know them buy a diferent name and ive probly seen a hundred of em before what do they look like ther not those big square yellow caps that i thought were or are "mkt's"

[Mooly]

Originally Posted by steptoe1111

sory mate but can you please tell me what a lytics is? i may posibly know them buy a diferent name and ive probly seen a hundred of em before what do they look like ther not those big square yellow caps that i thought were or are "mkt's"

And you are working on a SMPS scary

[steptoe1111]

Originally Posted by Mooly

Many SMPS don't run correctly (or as you expect) with no load. Some outputs may be switched or fall to a low value as the unit enters standby. 99% of problems are dried out electroylitics. Buzzing is usually the ferrite components, maybe because the drive is incorrect.

cheers mate i was considering replaceing every electrolic cap on the board as an option
for the sake of $10 bucs or so less hassle that way because i would have to remove them anyway to leak test them

[steptoe1111]

Originally Posted by Mooly

And you are working on a SMPS scary

ha ha ha ha mate i have adhd with ocd thrown in i love electronics and it keeps me sane if i posted some photos of my sound system i built over the last 4 years you would probably $#!t ya self
considering im self tought i recon im doing allright dont worry i know the risk's ive blow enogh crap up to know what not to do and isent funny if it dosent kill ya .... how much respect for electricity a good zap can give ya

[no gas]

Originally Posted by steptoe1111

sory mate but can you please tell me what a lytics is? i may posibly know them buy a diferent name and ive probly seen a hundred of em before what do they look like ther not those big square yellow caps that i thought were or are "mkt's"

lytic is short for electroLYTIC!
The caps you are pointing to are not tantalum, they are film caps. Tantalum caps max out at around 50VDC(with exceptions). As said before, they are .68uF at 450VDC.