Question about capacitors and how much they could be dangerous

[MaxSynths]

So my old Echo Layla 20 bit suddenly started to do a strange, gun machine alike, noise. Browsing the net I've found an old article by a guy which had similar problems and it turned out that this could be something related with capacitors.

After opening my Layla I've found that one of the capacitors was broken.
(There are 3 caps: 2x 1000uf 25v , 1x 10.000uf 16v).

At the end of the same article the author wrote a few lines of warnings about handling capacitors and that they could be very dangerous and they need to be discharged properly.

I've tried to gather specific informations but the topic is not very clear to me...

- The capacitor I have to replace is a 10.000uf 16v. Question: the energy inside of it could be so dangerous to seriously harms a person (or even kill a person! I've read some comments on the net that scared the s**t out of me)?

- Do I need to discharge the capacitor before disassembly it from the board?
(somewhere I've read that you have to discharge a capacitor tht HAS BEEN taken out of a board... and this makes me think that it's not necessary to discharge before).

- Let's say I have to discharge it: is it safe to use the bulb method?

- Question about the cap itself: what if I replace it with another one with a slightly different "v" value (let's say 25v)?


Thanks in advance,
Max

[werp]

http://www.repairfaq.org/sam/captest.htm

I love google

[MaxSynths]

http://www.repairfaq.org/sam/captest.htm

I love google

Thanks, I love it too...
I already seen that page, but I'm looking for an easy and fast opinion. It's way too difficult for me to read a ton of stuff with technical details just to do an easy job.

In short I only want to know what are the chances to see a "R.I.P. MaxSynths" thread tomorrow...

[Gamma-UT]

Maximum energy in that cap at full charge is something like 0.5 joule.

If it were a 400V cap in the back of an old TV, then I'd be concerned but this isn't going to kill you. Might sting a bit, so discharging before desoldering would be an idea as you're most likely to touch the pins getting it off the board.

As it's probably an electrolytic try not to get it hot while desoldering - they can fizz/burn/blow up. Wear eye protection.

It's hard to say whether the rated voltage matters but as it's probably in the PSU, I doubt the voltage rating is crucial as long as it's higher than the original and not that much higher. Stuff like ESR can matter more.

[MaxSynths]

Thank you Gamma-UT, nice info and advice!

It's hard to say whether the rated voltage matters but as it's probably in the PSU, I doubt the voltage rating is crucial as long as it's higher than the original and not that much higher. Stuff like ESR can matter more.

Ok, fine! Ehm concerning ESR... what is exactly? It's a value that can be read somewhere and that must be taken in consideration?

Already ordered another capacitor (damn hard to find!) and I have no idea what ESR is.

[werp]

I don't imagine for one second that a 16 volt capacitor has the capability of harming a person unless that person is fitted with a pacemaker...
I have had to replace circuit boards with large 240 volt capacitors in them used in motor start sequences. I'm unsure what the micro farad value was but they were 30 to 35 mm diameter and approx 75mm in height.
De-energizing of the capacitor was done by taking a deep breath and shorting the terminals out with an insulated screwdriver.
Usually the triacs on the board had already blown so circuit damage wasn't an issue.
I very much doubt you are in danger of harm with a 16 volt capacitor, assuming you are disconnected from the power source.

[MaxSynths]

I very much doubt you are in danger of harm with a 16 volt capacitor, assuming you are disconnected from the power source.

My doubt was the 10.000uf value which, I have to admit (I'm below the newbie level here, I think it's clear! ), I don't know what it means.

BTW thank you guys for the informations, I really appreciated your help!

[werp]

ESR = equivalent series resistance....probably low voltage control circuitry rather than power supply circuitry.

Google again...esr acronym.

[Gamma-UT]

At 10,000µF I imagine it's PSU, so the main thing is going to be having the right the capacitance, much more so than voltage or ESR. Surprised that 16V devices are hard to find though.

[werp]

Micro farads are very small units of measurement concerning capacitance..
To pu some perspective on just how small, The capacitance of the Earth's ionosphere with respect to the ground is calculated to be about 1 F.

[george]

Yes, capacitors can be dangerous. Handle with lots of care!

[werp]

16 volt capacitor games..
Not condoning this for one second but it doesn't look like it killed anyone.

http://m.youtube.com/#/watch?v=omFpKg0S ... mFpKg0SNCw

[werp]

Yes, capacitors can be dangerous. Handle with lots of care!

So that's where my eyebrow came from. My mum must have been a bit of a tart.

[MaxSynths]

At 10,000µF I imagine it's PSU

And you are right, It's a cap on the PSU board.

Surprised that 16V devices are hard to find though.

Well the availability of caps with these specs (10.000uf / 16V) seems very low! I live in Milano that is a big city, but after trying several shops I just quitted to search and tried on the web.

But the real problem was to find not only the right uf/v combination but also the right size (25mm x 25mm). I've found some caps which were a bit high in height but the problem is that above 25mm the cap would not fit into the case

In the end I've found the right one from a ebay dealer in the UK (after trying to order @ farnel only to see my order cancelled because was under 50€ ).

[MaxSynths]

Yes, capacitors can be dangerous. Handle with lots of care!

Only now I realize how much times I risked to be severely harmed...