Electronics question

markweatherill · 20 Sep 2010 at 17:38

I have a TV here with a couple of suspect 3300uf capacitors on the power supply board.

My local electronics superstore doesn't stock them, of course, but they do have 4700uf ones.

Is there any harm trying 4700uf in place of 3300uf capacitors?

PhillyDee · 20 Sep 2010 at 17:40

Nope, they will alter the characteristics of the circuit.

What voltage caps are they? The only change you can make is to increase the voltage rating or temperature rating of the caps.

Also, make sure that you discharge these capacitors properly! they can pack a powerful punch!

MikeHunt79 · 20 Sep 2010 at 17:49

You may want to try and match the ESR also, but 4700uF caps would most likely work really. I'm guessing it's a SMPS as opposed to a linear PSU?

p4radox · 20 Sep 2010 at 17:51

Firstly, be careful. You're likely to get a massive electrical whack if you're prodding live equipment.

In answer to your question: if they're just power supply bulk caps you could swap them with something of a similar capacitance and they'll be fine. 3300uF is large, so this is probably the case. If you want to buy an exact replacement (which is probably sensible) just go on Farnell and buy something with a suitable voltage rating.

Do you have any experience with this sort of thing?

Dr.EM · 20 Sep 2010 at 18:04

Sounds like bulk capacitors with that value. 4700uF should work in this case, ensure the voltage rating is equal or higher though. Small risk the input surge to charge them would cause nuisance blowing of the inlet fuse however, but unlikely with this small a difference I suspect.

markweatherill · 20 Sep 2010 at 18:16

Thanks for all the replies. I'll pop out and get a couple of the 4700uf ones and see what happens.
At worst it won't work and I'll need to order the correct value.

EDIT: fitted the two 4700uf capacitors and the TV has now turned on! Will need a 'soak test' to be sure, but early signs are good.