Tantalum capacitors

[cbp]

hello mates,
I need some advice.
I have an electronic board that has Tantalum capacitors, one of those is shorted.
the value of the Tantalum capacitor is; 33UF 35V.
The issue is that in my country we cannot get those capacitors.
That particular capacitor is placed on the board as a spike controller for the power source. ( 12 to 24 DC volts).
I think I can use a ceramic capacitor, staying with the 35 v and going a little bit higher 45uf value.
Space in not an issue.
What do you think ?
all ideas are welcome.
cheers...

[Meat-Head]

1) there poisonous

2) if its only 12 volt chop the board out, Tweeet off ebay
12 volt 4 amp switch mode power supply

3) what is it for?

[Johnner]

1) there poisonous

2) if its only 12 volt chop the board out, Tweeet off ebay
12 volt 4 amp switch mode power supply

3) what is it for?

.............

[Meat-Head]

.............

YES THEY REALLY ARE NASTY STUFF,

thats why daddy, before he died refered to them as transhlers (spiders)

[cbp]

hello mate.
the tantalum capacitor its installed in the internal power supply of an automotive scanner, it is not an external power supply, its part of the scanner main board.
I don't have the electrical diagram of the board, but looking at the connection of that capacitor it seems that its intended for ripple control of the power source of the scanner, which is the 12-15 volts of the vehicle diagnostic connector. The alternator of a giving vehicle sometimes produce enough ripple to affect or even damage such type of equipment.
So I guess, the capacitor is only to filter the ripple of the power source.
I hope I made myself understood.
thanks for the help.
cheers.

[alldecode]

which diagnostic scaner?

mybe delphi?

[cbp]

I do have a few Delphi....do they have similar capacitors ? uhmm...I am going to open one and will let you know.
The scanner with that tantalum capacitor is a Autoboss PC-MAx clone called VCS.
thanks for taking time to help me...
cheers...

[Hadron]

hello mates,
I need some advice.
I have an electronic board that has Tantalum capacitors, one of those is shorted.
the value of the Tantalum capacitor is; 33UF 35V.
The issue is that in my country we cannot get those capacitors.
That particular capacitor is placed on the board as a spike controller for the power source. ( 12 to 24 DC volts).
I think I can use a ceramic capacitor, staying with the 35 v and going a little bit higher 45uf value.
Space in not an issue.
What do you think ?
all ideas are welcome.
cheers...

You can't get a ceramic capacitor in that value (33uF or 45uF). It will need to be an electrolytic capacitor (either 33uF or 47uF @35v)

Tantalum capacitors are notorious for going short circuit, and also for blowing up!

[cbp]

Thanks Hadron.
I was not aware that multiple ceramic layer capacitors are not available in 33uf and 45uf...I looked around and so far I have not found such...
And please correct me if I am wrong, but using an electrolytic polarized capacitor would not be as good as a tantalum or ceramic, they are not as accurate or good filters for ripple noise reduction. And when they blow up they do a lot of mess...spraying all the stuff over the board....
But lets say that I am wrong, then what would it be the right value?
thanks for the help.

[Hadron]

Thanks Hadron.
I was not aware that multiple ceramic layer capacitors are not available in 33uf and 45uf...I looked around and so far I have not found such...
And please correct me if I am wrong, but using an electrolytic polarized capacitor would not be as good as a tantalum or ceramic, they are not as accurate or good filters for ripple noise reduction. And when they blow up they do a lot of mess...spraying all the stuff over the board....
But lets say that I am wrong, then what would it be the right value?
thanks for the help.

I tend to use the Panasonic FR series of low ESR 105?C electrolytic capacitors for all my PSU repairs. They should work fine for your repair. Here's a couple of Ebay 33uF 35v sellers:-

http://www.ebay.co.uk/itm/3515205301...%3AMEBIDX%3AIT
http://www.ebay.co.uk/itm/3513138178...%3AMEBIDX%3AIT

I have always had bad experiences with tantalums. At work, we had some that literally exploded into flames when the boards they were in were switched on, despite being connected correctly & being within the voltage limit.

I've also fixed many types of test equipment built in the 70's, 80's 90's that have failed due to short circuit tantalums.

The chances of an electrolytic capacitor of this value exploding is very unlikely, providing it's connected the right way round & doesn't exceed 35v. The larger values are more prone to internal gas build up & so have a vent in them to stop them exploding.

[cbp]

thank you very very much Hadron.
I had also my issues with tantalum caps...in emissions benches and also scanners.
I had the idea that they were more reliable, but now with your advice and other comments I found at the web I think I will start to change those with Panasonic FR?s.
Those Panasonic capacitors are really easy to get here...they are very common, now I know why they still exists and many techs use them instead of tantalum.
I have a new emissions board from Andros and they don't use tantalums any more...they use Panasonic Caps !!! Now I know why.....
One last question..when you say * The larger values are more prone to internal gas build up* do you mean higher uf or volts? or both?, and also when you say * so have a vent IN them to stop exploding* do you mean to vent the case I which the board is installed right?
thanks for your kind help.
cheers..

[Hadron]

...One last question..when you say * The larger values are more prone to internal gas build up* do you mean higher uf or volts? or both?, and also when you say * so have a vent IN them to stop exploding* do you mean to vent the case I which the board is installed right?
thanks for your kind help.
cheers..

The capacitors which are physically larger due to their higher uF values have the vents in them (e.g. 470uF 35v, 1000uF 25v, 2200uF 16v).

The vents are in the top of the capacitor, usually in an X shape or K shape. If hydrogen builds up inside the case of the capacitor, the top of the capacitor will usually bulge first, then the seam of the vent will split open, preventing the whole capacitor from exploding. Sometimes the rubber bung at the bottom of the capacitor might be pushed out before the vent splits, spilling electrolyte onto the circuit board.

[alessioblaupunkt]

Don't you have Distrelec/RS component in your country?
They have quite high shipping cost but they have tantalum capacitor.

If you have to use FR buy 33uF 50V so you give some relax to the capacitor.

[cbp]

I followed Hadron advice, worked perfect, ripple was reduced a lot.
I am thinking about alessioblaupunkt advice, sounds like a good idea too.
Happy new year to all !!!
thanks for all the help and advices...
cheers.