Capacitors 101

[Stevie D]

TV on bench with vented main filter cap, (220uf @ 200v), and I've a
simple query. Can I up the ante on this and replace with a 470uf @
200v? It's a switched mode p. supply and the pop was a result of a
power surge, didn't take anything else out. Is it just a question of
economics when it comes to filtering, (cheap walmart tv), or might I
disturb the fragile balance in the smps. My thought is, better filter,
smoother dc. Any thoughts???
Cheers, Steve

 

[DaveM]

TV on bench with vented main filter cap, (220uf @ 200v), and I've a
simple query. Can I up the ante on this and replace with a 470uf @
200v? It's a switched mode p. supply and the pop was a result of a
power surge, didn't take anything else out. Is it just a question of
economics when it comes to filtering, (cheap walmart tv), or might I
disturb the fragile balance in the smps. My thought is, better filter,
smoother dc. Any thoughts???
Cheers, Steve

Well, your thought is correct about smoother DC, however, there are other
considerations that are important as well. Inrush surge current is the first
thing that comes to mind. When you first apply power to an uncharged capacitor,
it looks like a dead short across the line. The higher the capacitance, the
higher the surge current. If the surge is large enough, you'll blow the line
fuse. Unless you just like digging around in a dead TV set just to change the
fuse every few times it's powered on, it would definitely be a nuisance.


--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some days you're the dog, some days the hydrant.

 

[Eeyore]

The higher the capacitance, the higher the surge current.

Within certain limits. More likely it'll make the inrush current last longer, which
could indeed also blow the fuse.

Graham

 

[Stevie D]

Graham, Dave, thanks for the input. I'll consider replacing the cap
with the initial value just err on the side of caution and avoid a call
back. This being said, I've had better luck in the past with closer
values, within 100uf or so. Happy Holidays

 

[Sam Goldwasser]

Graham, Dave, thanks for the input. I'll consider replacing the cap
with the initial value just err on the side of caution and avoid a call
back. This being said, I've had better luck in the past with closer
values, within 100uf or so. Happy Holidays

I also wonder if the cap is the only problem.

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[Stevie D]

Thanks for the feedback/comment Sam, I've had the set on now since I've
replaced the cap, no more "poof"! The client lives in a rural area with
frequent surges in the supply line, (transmission lines affected by ice
storms and the like, I'm in Canada ya know...eh). Pretty straight
forward repair. Merry Happy Joyous Holidays one and all, health and
happiness in the new year!
Cheers, Steve

 

[Spehro Pefhany]

TV on bench with vented main filter cap, (220uf @ 200v), and I've a
simple query. Can I up the ante on this and replace with a 470uf @
200v? It's a switched mode p. supply and the pop was a result of a
power surge, didn't take anything else out. Is it just a question of
economics when it comes to filtering, (cheap walmart tv), or might I
disturb the fragile balance in the smps. My thought is, better filter,
smoother dc. Any thoughts???
Cheers, Steve

Going higher on working voltage is a better (and very safe bet), but
probably it was just a cheap physically small capacitor and replacing
it will do the trick.


Best regards,
Spehro Pefhany