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Discharging capacitors that are soldered into place

JMiP

JMiP

AK Subscriber
Subscriber
There are plenty of videos on YouTube showing how to discharge capacitors, but none of them (at least the ones that I have found) show how to discharge a capacitor that is soldered into place. Can anyone share the proper way to discharge a capacitor that has been soldered into place? Or is this not even a concern?
 
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But what if the cap's leads are buried under a pile of solder? I assume you can discharge the cap by touching the discharger's leads to the piles of solder. Would that be a correct assumption?

Also, the article in mkane's linked article says to use a 10K 2W resistor when creating the discharge wire. This guy on YouTube is saying to use a 470 5W resistor and there is only a single lead with which to touch the cap's leads. It gets rather confusing with all of the different information out there.
 
Your assumption is correct, any connection to the cap's leads will work.

The value of the resistor is not critical. I like to use a piece of wire or a meter lead and put the resistor on one end. The opposite end is then momentarily touched to ground. This avoids having the resistor in hand or touching the cap's leads.
 
westend said:
Your assumption is correct, any connection to the cap's leads will work.

The value of the resistor is not critical. I like to use a piece of wire or a meter lead and put the resistor on one end. The opposite end is then momentarily touched to ground. This avoids having the resistor in hand or touching the cap's leads.
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I gotcha. I think I will make a discharge wire this weekend. Or maybe I'll order a bunch of stuff to make my own speaker wire and make the discharge wire at the same time. That way, they all match.
 
I would suggest reading around and learning a bit more before working on amps. The question and comments made demonstrate a lack of very basic circuit and materials knowledge.

What i suggest is work on projects were safety is not an issue until you get the hang of basics. You will get on top if it but dont work on high voltage stuff like main amps.
 
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smurfer77 said:
I would suggest reading around and learning a bit more before working on amps. The question and comments made demonstrate a lack of very basic circuit and materials knowledge.

What i suggest is work on projects were safety is not an issue until you get the hang of basics. You will get on top if it but dont work on high voltage stuff like main amps.
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Sounds like good advice.
 
smurfer77 said:
I would suggest reading around and learning a bit more before working on amps. The question and comments made demonstrate a lack of very basic circuit and materials knowledge.

What i suggest is work on projects were safety is not an issue until you get the hang of basics. You will get on top if it but dont work on high voltage stuff like main amps.
Click to expand...

Yep, agreed. I feel comfortable doing basic stuff like cleaning, but when it comes to things like this, I'm out of my depth. That's why I ask such questions. Also, as stated above, it seems like everyone has competing opinions when it comes to working with electronics.

Is there such a thing as a kit for adults that teaches electronics in a way that gives you hands-on experience? I know that there are kits available, but it seems like they are mostly geared to kids. But hey, if they are actually effective, who am I to scoff at such things?
 
JMiP said:
Yep, agreed. I feel comfortable doing basic stuff like cleaning, but when it comes to things like this, I'm out of my depth. That's why I ask such questions. Also, as stated above, it seems like everyone has competing opinions when it comes to working with electronics.

Is there such a thing as a kit for adults that teaches electronics in a way that gives you hands-on experience? I know that there are kits available, but it seems like they are mostly geared to kids. But hey, if they are actually effective, who am I to scoff at such things?
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For sure, and i don't want to discourage you at all. Aside from safety, it's also more fun to feel progression rather than jump into the deep end and not know what is going on.

No need to start with kids kits. You can get straight into fun and usable audio projects. Something powered by a battery or switched-mode power supply (your standard power packs that plug into the wall can give you DC) will be the trick, so dealing with mains voltage and power supplies can be avoided. If you listen to headphones you could make a portable headamp like the cmoy or similar, or there are lots of great desktop headphone amps. Or a preamp, if that appeals more than a headamp. There are excellent phono preamp kits if you listen to vinyl. Other things that are safe to work on could be rebuilding the passive crossover network in some vintage speakers. Once you do a bit and get use to working with circuits and understanding multimeter measurements and safety, everything will start to make sense and then you can think about working with other stuff. Stay away from tube projects since they (usually) use high voltages :)
 
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Not knowing that solder is conductive ... I think we can safely assign you "newbie" status ...

(Just gave myself a virtual kick for saying that so you don't have to) <G>

My favorite old adage is "keep one hand in your pocket when working on high voltages". Just a friendly reminder that whatever you do, don't ground yourself when poking around charged components. Even if you're careful, that can get interesting sometimes ... I've had a spark "jump" over a couple inches when passing a hand by a "hot" cap or tube anode. Got the scars to prove it!
 
sKiZo said:
Not knowing that solder is conductive ... I think we can safely assign you "newbie" status ...

(Just gave myself a virtual kick for saying that so you don't have to) <G>

My favorite old adage is "keep one hand in your pocket when working on high voltages". Just a friendly reminder that whatever you do, don't ground yourself when poking around charged components. Even if you're careful, that can get interesting sometimes ... I've had a spark "jump" over a couple inches when passing a hand by a "hot" cap or tube anode. Got the scars to prove it!
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Well, I kind of "knew" that solder was solder was conductive, but I wanted to know for sure. All of the YouTube videos that I watched on the topic of discharging capacitors, not a single one showed someone doing that with a cap still soldered in place. The vast majority of those videos showed discharging caps that were just sitting on a table, and the majority of those are of a bunch of yahoos doing it just to see how big of a spark they could create. The Internet iz dum.

But yeah, I'm a total n00b when it comes to this type of thing, but I want to learn and I want to learn the correct way.
 
All it took for me was one time getting hit with a 370 v Capacitor and I learned to respect them! Went in one arm and came out the other and 15 minutes of saying SH## that HURT! I don't like Capacitors!
 
I'm not always anxious to discharge caps that are connected to a circuit. For example, let's say you have a main filter cap feeding a common three terminal regulator that also has a cap on the output, a common scenario. If you discharge the main filter cap, the regulator will be destroyed by its output cap. Datasheets show how to use diodes to protect the regulator from such events, but it's rare to do so because nobody anticipates somebody shorting out the filter caps. Other circuits and ICs can present similar problems. If you're going to discharge lower voltage caps on solid state equipment, use a big enough resistor such that the process goes slowly, say ten seconds or so.
 
There's a good chance that capacitors soldered to a circuit board will have a discharge path anyway and simply waiting a minute or two will give them enough time to discharge. A check with a voltmeter will tell you if that's the case or not.
 
ConradH.. he knows his 'sh*t on caps!!. My flip is bringing unit sitting for ages and expecting like "instant on". like off the shelf or garage sale is supposed to function like a warranty unit new. ya blow something else in the process. because the system isn't up to reset or getting 'motivated' by the caps in sub circuits.. as an example.

ConradH.. glad to see you're about! :D

edit point: Mains caps can hold up a charge very fast just plugging a unit in.. 63v rated mains? I've unsoldered a couple not discharging them? Just forgot? blew a meter off the scale! Still held the charge for two weeks! I connected the second cap on my dbt just to watch the bulb glow dim with a 100 watt bulb. still a hell of a charge.

edit point 2: I've also discharged caps down to circuits with many 15-30 rated caps to get all the charges off those, too. they had a few ic circuits etc. logic a few. protection circuits to reset also. Just saying that the 30v or lesser caps in circuit still also hold a charge. Can make your meter readings go askew.
 
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