*Broken-- Capacitor Filter question?? 56,000micro F, 50V??

[cjchands]

Hi guys,
I brought cnchobby few months back, and the machine was working fine.
I just recently have problem with FILTER CAPACITOR that seem to be broken, it doesn't charge up and need to replace it.

1. Any source of where might I find it for cheap?

2. Any idea why is 56,000 micro F 50V? (50V is the max of Capacitor rating), but why 56,000 micro Farad? I thought the filter R-C filter is used for AC circuit,but this CAPACITOR is coming out from the bridge rectifier which already DC circuit isn't it? Moreover, it connected in parallel with 2K (4W) resistor. Hmmmm....

Thank you in advanced for experience knowledge user.
Jeff

[Al_The_Man]

Originally Posted by cjchands I thought the filter R-C filter is used for AC circuit,but this CAPACITOR is coming out from the bridge rectifier which already DC circuit isn't it? Moreover, it connected in parallel with 2K (4W) resistor. Hmmmm....

Is this a catch question?

The R-C filter on the AC line is 'Trap' for noise or spikes which otherwise might be passed through to the electronics and cause damage.
The 56k µfd cap is to smooth the otherwise 120hz DC ripple coming out of the bridge, this cap. attempts to keep the level of the DC voltage 'pure' or constant.
The bleed resistors function is to provide a dis-charge path when the PS is switched off.
BTW, Why do you think it is not charging?
Al.

[cjchands]

Al,
The guy that used the machine told me that he thought it might be the capacitor that is broken...I just took his word. But he said there is weird noise coming out from the CAP.
I was also currious in why you need 2K Resistor in parallel with Capacitor though coming out from the DC...but thanks to you.
Thanks for the explanation, now if I could find where to get this CAPACITOR.

[Al_The_Man]

DigiKey 338-1243-ND
Al.

[cjchands]

I tried to find the replacment for the big CAPACITOR on surplus website, but unable to find the exact same rating.
Plus, how do you know figure out the dimension size of that big CAP?

[cjchands]

Oh, I didn't see your link that you recommended..
However, they seem to sell QTY 10 per package..
darn....don't know what I would do with other 9 QTY.
Thanks though.

[epineh]

Originally Posted by cjchands I tried to find the replacment for the big CAPACITOR on surplus website, but unable to find the exact same rating. Plus, how do you know figure out the dimension size of that big CAP?

If you find something close you will be fine, go higher values. You can put larger caps in this instance without probs, but I wouldn't put lower voltage or uF ratings in, proper cap selection is a whole story in itself, but get close as you can and you will be fine.

Good luck.

Russell

[Al_The_Man]

Originally Posted by cjchands However, they seem to sell QTY 10 per package.. darn....don't know what I would do with other 9 QTY. Thanks though.

I think DigiKey 'Standard Package' is mis-leading, I have never had a problem of buying one-off of any thing there. You will notice that they price out per 1 of.
Al.

[ivirscar]

You can even go to mouser.com and purchase 2 33,000uf 63volt caps and wire them in parallel to achieve a better result of capping the ripple than just the one piece that you now have.
With capacitors, the amount of voltage rating is not critical as long as the rating you use is AT LEAST 10 volts MORE than your supply is expected to deliver. In the case of the 24 volt transformer rated at 10 amps, a 63 volt capacitor is best and using 2 33,000 in parallel will cover your DC ripple just fine for most all the cnchobby driver boards.


Brenon