How important is the value of a filter cap?

modessitt

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I have a Makvision chassis with a hula issue. The chassis buzzes while it does this, but otherwise gives a good pic.

The filter cap has a domed top. I cut through the wrapping and removed the "bubble" top, and it is definitely domed, although it doesn't appear that the vents have split, but it's definitely not flat as caps normally are. Still, I want to replace it to see if it helps the hula problem, as the VR and rectifying diodes seem to be okay.

The filter cap is a 330uf 400v cap. I have a 270uf 400v cap handy, but don't know if I can use it. All my parts chassis' are elsewhere, so I can't look through them.

What to do???
 
Most filter caps can be subbed at +10/-20% of their value.
 
-20? Okay. I was thinking -10 and that gave me 297.

Anyway, the 270u 400v worked just fine. No more hula or buzzing. I assume that it's okay for me to leave that value in there?
 
BTW - it seems Makvision uses a different polarity marking setup than other monitors. Usually, on a WG or other chassis, the cap location will sometimes have a circle with one half filled in black. You install the negative lead in the black side. However, on the Makvision, you install the POSITIVE lead in the black side.

I put in the filter cap and got no power at all. Since there is no + on the chassis, I had to look at some other caps to realize my mistake...
 
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