Anyone know if SAMWHA Caps are Good??and other questions??

Hi Folks, I just bought 20 Samwha 10,000uF 63v High G Low ESR 85c Electrolytics for about $1.25 each and was wondering if these are good quality Capacitors?? I was going to use them for Power supply Filtering....

They were a Fraction the Price of any other Caps in this Value I could find so I bought all I could get from this seller...

Here is the auction I got them from which has a pic of the caps....

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&ih=020&sspagename=STRK%3AMEWN%3AIT&viewitem=&item=300046047117&rd=1&rd=1

Another question I have is sometimes I see schematics for Power supplies were the Filter caps go between the + and - supply rails as opposed to going from the Supply rail to ground...

Are there any advantages to doing it this way or any disadvantages??

Also If I were to do it that and Put say a 10,000uF cap between the + and - Suply rails would that constitute 10,000uF on each Rail as each rail is connected to the same 10,000uF cap?? If so then it seems like a Good way to use half the Caps and get the same filtering, Or am I totally off base here.....


Thanx for being gentle with this newbie....



Cheers

I had a good stock of Nichicon 10,000 Uf 50 V and at surplus prices
I SOLD OUT at $1/50 each so your .85 ea is a great deal, I should
state the Nichicon's I had were 105 degrees rather than the normal
85 degress...
I do have a large stock of Samwha 22 Uf 450 V axials at $1.00ea
and these are at 105 degrees and have been told my major guitar
amp manufacturers that they love them and I keep selling them more.
SO, you made a good deal...

Steve @ Apex Jr.

Hi, I actually just checked on the net to see what these caps go for and in singles they go for as Much as $15 each (8 Pounds sterling) and for quantities over 100 they go down to about 5 Pounds Sterling ( I don"t have a Pound sign on my keyboard)...

So I guess I did get a good deal.....

Cheers

Minion

I bought a bag of Samwha 220uF/25v caps from a clear out & I had a lot of trouble with them. I used them for PSU decoupling on a few projects but threw them away after a few of the caps failed. I built a PSU for a Rockman for a buddy & 2 of the 4 caps I used failed & had to be replaced.

Sorry to be a downer, but I shudder when I see the odd Samwha in my spares box....... :sad:

Maybe yours will be better than the ones I got.

Peter

[quote author="peterc"]Minion

I bought a bag of Samwha 220uF/25v caps from a clear out & I had a lot of trouble with them. I used them for PSU decoupling on a few projects but threw them away after a few of the caps failed. I built a PSU for a Rockman for a buddy & 2 of the 4 caps I used failed & had to be replaced.

Sorry to be a downer, but I shudder when I see the odd Samwha in my spares box....... :sad:

Maybe yours will be better than the ones I got.

Peter[/quote]


Well if they turn out to be bad then I didn"t loose out on too much money...

The guy who I bought them from got them when he was in Japan and he used what he needed and sold what he had left over so hopefully they will work out OK.....

Do you guys know about any (dis)advantages to useing Filter caps that go between the supply rails over ones that go from the Supply rails to Ground....

Someone over at Gearsluts or Diyaudio told me that if i Put a 10,000uF cap between the supply rails then it counts as 10,000uF on each rail, were If I put the Cap between the supply and ground I would have to use One 10,000uF cap on each Rail there for useing twice as many caps to get the same amount of filtering.....

Is there any credance to this suggestion??


Thanx

Yes, he forgot you drive a load, not just consume currents from rail to rail.

The people who said that putting one 10K uf between the rails was equal to one 10K from each rail to ground were wrong.

So if I put a 10,000uF cap between each rail does it count as 5000uF per rail then??

Is it best to use a combination of the 2 filtering schemes or is one superior to the other??


Thanx

[quote author="Minion"]So if I put a 10,000uF cap between each rail does it count as 5000uF per rail then??

Is it best to use a combination of the 2 filtering schemes or is one superior to the other??[/quote]
It depends on the power supply design and the type of load. A capacitor is basicaly an energy store which is used to provide current peaks when the load demands them. If the load is such that a peak demand on its +ve supply is mirrored by the same current returning via the -ve supply, then a cap beteen +ve and -ve rails would be able to supply some of this energy.

However, in the many cases (e.g push pull outputs) a current peak in the +ve supply returns via the 0V on one half cycle of a waveform and is followed by a -ve peak returning via 0V on the following half cycle then a cap between +ve and -ve rails may actually be detrimental to the circuit operation.

As a rough rule I would say if the circuit being powered is entirely class A then placing a cap between +ve and -ve rails is probably OK. Anything else may make matters worse.

Ian

Well that makes sence, I will just keep the Caps from supply to ground just to be safe...


Thanx

For cap info, go to FaradNet

Samwha is a Korean company with a wide range of caps. You need to look at the data sheets and make proper choices for the application.

Hmm...not finding the specific data there. Go to their website and download a catalog or datasheets.

Samwha Capacitors

or straight to the the PDF files:

Samwha Cap PDFs

HC series is the lowest grade in their Large Aluminum Electro series, though they can go up to 500V.

A better choice perhaps --> The WL series is high reliability (5000hr), Low Impedance, up to 450V, and rated to 105 degrees C.

Peace!
Charlie

Actually I just recieved the Caps and they are the HC series which are the Cheaper ones....But for $1 for a 10,000uF I still got a Good deal especially considering my local electronics shop charges about $3 for a single genaric 1000uF cap....I will be running them at less than half there rated voltage so they should last longer than running at full voltage....


Thanx for the Info.....Cheers

[quote author="Minion"]Actually I just recieved the Caps and they are the HC series which are the Cheaper ones....But for $1 for a 10,000uF I still got a Good deal especially considering my local electronics shop charges about $3 for a single genaric 1000uF cap....I will be running them at less than half there rated voltage so they should last longer than running at full voltage....


Thanx for the Info.....Cheers[/quote]

Test them for leakage current and see how fast they stabilize. If the materials and construction are poor then the leakage will tnd to be high and unstable. If so, run like hell.

I've had my share of problems with crappy 'lytics. The best 'lytics are so much better than their barn-door CYA specs allow them to be, it's not even funny---and those are what you want to use if you can.

How do I test for leakage current?? Can it be done some way with a DMM?? That is all I have as I can not afford a scope.....

I read the Data sheet for these Caps and the leakage current in the Datasheet doesn"t seem bad, No worse than any other standard Lytic as these are the "General Purpose" type caps.....

Are those Big "Computer Grade" caps any good?? You know the ones that are like 6 in tall and 2 in wide with the screw terminals on top?? Cuz I can also get those for a Good price (about $3 for a 22,000uF computer grade cap)??


Thanx

Minion,

I have yet to see large-value caps such as yours (10,000uF) connected directly between the +V and -V rails in a PSU. In all the PSUs that I have seen/designed/fixed, etc, the smoothing caps have always been from +V to 0V and 0V to -V....... it's just the way it's done.

What I have seen done is to have low-value electrolytics (2u2 50V) between the +V and -V rails locally to op-amps, especially 5532's, which need to be locally decoupled for best-performance. This cuts the quantity of decoupling caps in half (maybe that's why the likes of Soundcraft have done it :wink: ), but of greater importance technically, is the point that current that is sucked from the +V rail is dumped into the -V rail and NOT into the ground rail.