rubber gloves...

zenocha · Post by **zenocha** » Tue Jul 15, 2003 1:25 pm

I've read a lot about the dangers of opening your psu to replace the fan on this forum . I am seriously considering doing this, but i do have some concerns.

Anyway i was thinking (please tell me if im way off with this) but surely a pair of household rubber gloves (washing up gloves) would provide enough insulation to protect you from the dangerous charge in the capacitors.

I welcome anyone to prove me right or wrong.

POLIST8 · Post by **POLIST8** » Tue Jul 15, 2003 1:29 pm

Do you have a spare PSU?

Unplug the one you want to work on and leave it unplugged for a day or two.

You're just snipping wires and splicing new ones in. You're not sticking crap into capacitors...

zenocha · Post by **zenocha** » Tue Jul 15, 2003 1:37 pm

im well aware of what is involved, it was just a thought to be sure of safety, anyway, its not essential at the moment as i am recieving a new psu tomorow for my old pc (6yrs old) as the other one chucked it, so i can replace the fan in that with no problem as it will have no charge having never been used, it more concerns my new pc, as a) i have no spare psu b) i use my pc everyday and c) i cant be bothered waiting a couple of days for it to discharge

lenny · Post by **lenny** » Tue Jul 15, 2003 1:52 pm

zenocha wrote:Anyway i was thinking (please tell me if im way off with this) but surely a pair of household rubber gloves (washing up gloves) would provide enough insulation to protect you from the dangerous charge in the capacitors.

I don't have any data on this. I would imagine it should at least provide enough protection from serious injury (unless you have a pacemaker or such, of course). However, I find that my fingers feel a lot more clumsy in gloves, and that may be more dangerous than simply being careful around an open power supply.

Oh, and a pair of plastic tweezers for tight spaces will probably be helpful. Sometimes the damn fan connector just doesn't want to come out.

aphonos · Post by **aphonos** » Tue Jul 15, 2003 2:11 pm

zenocha wrote: so i can replace the fan in that with no problem as it will have no charge having never been used

Do you think you might want to test the new PSU as stock before you mod it to make sure that it is not DOA?

Perhaps I've been fortunate, but I have opened my Seasonic after as little as 10 minutes unplugged and have even handled and removed the PCB. I'm careful to avoid capacitors though and try to keep my fingers on the edges of the PCB whenever I have to move it.

Keel · Post by **Keel** » Tue Jul 15, 2003 2:18 pm

zenocha wrote: Anyway i was thinking (please tell me if im way off with this) but surely a pair of household rubber gloves (washing up gloves) would provide enough insulation to protect you from the dangerous charge in the capacitors.

I dunno about the protection of rubber gloves but I agree with lenny that it'll be clumsy doing the mod with the gloves on. Since you're worrying about protection so much why not just buy a new psu? $50-100 isn't worth a trip to the hospital.

zenocha · Post by **zenocha** » Wed Jul 16, 2003 1:15 am

trouble is, i dont have that sort of money, or even the UK equivelant, especially not for just one item as im only 15 and have very little money to spare. I am not actually particularly worried about doing the mod, as I have plenty experience in such things, well for a 15 year old anyway.

All i really posted this topic for was to see if there was a way of doing this mod more safely than just "being careful"

aSe · Post by **aSe** » Wed Jul 16, 2003 3:25 am

Why are you so worried, just don't touch the bottom of the capacitors that connects into the pcb. Its not like a live CRT. Open that sucker up, try to avoid touching things other then the fan and fan header. I've modded several of mine, some 2 or 3 minutes after last being used. If you do get a sock, next time don't touch that.

Pjotor · Post by **Pjotor** » Wed Jul 16, 2003 3:32 am

I think this tip has been given before, but here goes:

1. Turn the computer off.
2. Unplug the mains cable from the power supply (yes, even it is equipped with a switch).
3. Press the on button on the computer a few times.

Pressing the on button will draw the remaining current from the capacitors in the PSU. The computer should start and stop while this happens.

energy · Post by **energy** » Wed Jul 16, 2003 6:31 am

Why are you so worried, just don't touch the bottom of the capacitors that connects into the pcb. Its not like a live CRT. Open that sucker up, try to avoid touching things other then the fan and fan header. I've modded several of mine, some 2 or 3 minutes after last being used. If you do get a sock, next time don't touch that.

All half decent PSUs have resistors across the capacitors to discharge them within a couple of minutes. Some don't however, and you dont need to touch the caps to get a shock - the primary (near IEC connector) heatsink is usually 300vdc live.

I too have opened PSUs right after powering down, as well as accidentally touching the heatsinks. Never had a problem, but you never know if the particular PSU has working draining resistors.

zenocha · Post by **zenocha** » Wed Jul 16, 2003 10:01 am

thanks for all your replies, but i did it before i even read a few of your posts, even without gloves!

It works great, i put a zalman in but with the resistor it wouldnt turn over so i had to scour (i hope thats how you spell it) my room for a lower value resistor, stuck that in and it works a charm, so now my old pc or jim as hes known is practically silent, now to move onto the the far more challenging bob, my new pc.

POLIST8 · Post by **POLIST8** » Wed Jul 16, 2003 12:00 pm

Your new PC should be easier since you're starting from scratch, you have the ability to purchase all the right products with much less customization.

zenocha · Post by **zenocha** » Wed Jul 16, 2003 12:05 pm

i say new, i mean not as old as my old one, its about a year old now, and i got it before i found out about quietening pc's, so its already choc-full of noisy equipment

POLIST8 · Post by **POLIST8** » Wed Jul 16, 2003 12:09 pm

Ah...

Yes, I had the same problem with mine.

Things have come a LONG way though, and with the help of eBay and other customers, I have had the ability to get rid of my other products while helping fund my silent passion.

Zhentar · Post by **Zhentar** » Wed Jul 16, 2003 2:01 pm

I personally have never been shocked working with PSU fans.... since your 15 I doubt you'll have any conditions that would make getting shocked dangerous, just painful.

One way to drain the PSU is with a PSU tester. I was at compUSA the other day and saw a couple for 15 dollars; leave it plugged into one of those for a minute or two and it should drain any charge.

larrymoencurly · Post by **larrymoencurly** » Thu Jul 17, 2003 9:59 am

Won't the PSU's +5V standby supply drain the capacitors in about 15 seconds (the wait before I hear a chirp or buzz)?

Those approximately 200K resistors across the capacitors will drain them in about 1,000 seconds (5 x 200K x 1000uF).

POLIST8 · Post by **POLIST8** » Thu Jul 17, 2003 10:03 am

The CPU fan in my ABIT KX-333 motherboard absorbs the rest of my juice...

dago · Post by **dago** » Thu Jul 17, 2003 10:37 am

quoting myself in another discussion :

First, I touched once a capacitor while the psu was running (!!!) and the shock didn't hurted me more than a 220V shock (IIRC). For the anectode, this psu was heavily dremelized and now has a big yellow sticker on it.

Now, if you want to be safe, a better solution is to
- isolate the psu from the ground (say on a wood/glass table)
- isolate yourself from the ground (good rubber shoes or books)
and ... most important
- keep your left hand in your pocket ... always !

and you can touch anything without being shocked

POLIST8 · Post by **POLIST8** » Thu Jul 17, 2003 10:51 am

I'm Left handed though...

fractal · Post by **fractal** » Mon Jul 21, 2003 5:29 pm

POLIST8 wrote:I'm Left handed though...

Does not change the rule. Left hand in pocket.

For those who don't know the basis of the rule ... electricity does not flow without a closed circuit (this is the reason birds can sit on a high tension wire and be charged with 100,000 volts but with no closed circuit they are unhurt). The two most common circuits through a human body are from hand to foot or from hand to hand. This is one reason that you should never stand in a puddle of water when operating electrical appliances.

Anyhow, by having a hand in your pocket, either hand, you block the path from hand to hand through your heart. Thus having your right hand in your pocket will work as well as having your left hand in blocking the hand to hand path through your heart.

By having your left hand in your pocket, you block the path from your left hand to ground via either foot, through your heart. Current passing from your right hand to ground via your feet does NOT go through your heart meaning the current does not stop your heart from beating.. Current passing from the left hand to ground via your feet DOES go through your heart, stopping it from beating and hence stopping you from living

al bundy · Post by **al bundy** » Mon Jul 21, 2003 6:42 pm

fractal, I've never heard that advice before but I am very glad to know it now.

Thanks for taking the time to pass that info along, it is much appreciated.

Safety first, always.

halcyon · Post by **halcyon** » Mon Jul 21, 2003 11:04 pm

I have one word of warning:

AC current passing through your hear at 50 or 60 Hz will most likely NOT stop your heart, but put it into a ventricular fibrillation (arrythmia). You will die within few minutes, unless there is a medically trained person with heart jump starting device around (to defibrillate your heart with a jolt of DC current).

You cannot stop VF with a chest massage like you may be able to revive a stopped heart.

As such, it is very dangerous and all high current/high voltage AC devices should be fixed by trained persons only, preferably connected to a safety transformer and working with one hand behind the back at all times.

So, now that I've scared you, yes I've also fixed my own PSUs. No, I'm not a trained electrician. And yes, I've even used rubber gloves, although I've been working on a wooden floor and with one hand at a time (takes patience, you can switch your hands). I also discharge the PSU using the disconnect + turn on Motherboard power a few times.

But having once been shocked from hand to feet (and apparently survived), I don't want to experience it again. Nor do I want any of you feel the same or worse.

Safe modding everyone!

regards,
Halcyon

dago · Post by **dago** » Mon Jul 21, 2003 11:25 pm

Thanks halcyon and fractl for expanding on my answer, I'm definitely not good enough for well-written long comments

Anyway, just to add two details ...

First is (shoud be ?) well known : "It's not the volts who kill, but the amps*", so, the value to take into account is the intensity ...

Second it that, this 'limit' intensity can vary from 5 to 200 mA (IIRC), which is a quite large range and is highly dependent on
- the path of the electric
- if the heart is near the path, the 'phase' of the heart at the shock time.

Of course, you can have a lot more problems than just heart (e.g. burned), but I think modding a PSU is not so dangerous compared with working with multi amp currents during an university lab the day after ...

Oh, yes, there's another thing to be carefull : do not touch other people (can be quite funny to see 3 person having a schock together), but at computer geeks are usually lone freaks, that should not be a problem

* that goes through your body (this precision is only meaningfull for HF)

nbac · Post by **nbac** » Tue Jul 22, 2003 12:19 am

halcyon wrote: AC current passing through your hear at 50 or 60 Hz will most likely NOT stop your heart...

True, but once your PSU is unplugged, it vill most likely not hold any AC-
current.

al bundy · Post by **al bundy** » Tue Jul 22, 2003 2:02 am

Reading all of this has finally inspired me to make this post over in the Site Feedback section, in case anybody is interested (?)

halcyon · Post by **halcyon** » Thu Jul 24, 2003 9:06 am

nbac,

yes, that is true AFAIK (for unplugged PSU with only charged cap released current).

However, as people tend to mistakenly leave their PSUs plugged in and also knowingly MOD their live PSUs (e.g. adjust potentiometers, make measurements), I though this was a useful tidbit to add.

That is, do not mess with live AC current.

Also, the frequency of the AC here is the culprit. If it was significantly different, it would probably stop the heart instead of putting it into VF. With a stopped heart, your spouse/sibling/parent could revive you (with luck).

So, the old saying could also be modified to state:

"It's not the volts that kill you, it's the interplay of current with frequency of the AC"

regards,
Halcyon

PS Al, great idea in the other thread!

larrymoencurly · Post by **larrymoencurly** » Sat Jul 26, 2003 12:41 pm

I've been told not to trust rubber gloves unless they're very thick and tough and have been tested just prior to use. Apparently one problem is that the hands get so sweaty that if a break does occur, the shock is sometimes worse than if the person had touched the high voltage without gloves. I'm not saying you shouldn't use protection, only that it's a lot safer to unplug the PSU and leave it alone for at least twenty minutes so the bleeder resistors can drain the capacitors in case the rest of the circuitry doesn't do that in twenty seconds. Take off the PSU cover, and, without touching anything, look around for burn marks or ruptured parts, and if there aren't any you can be almost certain that the capacitors have been drained by those two methods. But you could also try measuring the voltage between the exposed metal on the tops of the capacitors and the case.

Gandalf · Post by **Gandalf** » Sat Jul 26, 2003 1:41 pm

fractal wrote:
Does not change the rule. Left hand in pocket.

That's always a good rule, when you can spare the hand that is. Caution is important though.

fractal wrote:By having your left hand in your pocket, you block the path from your left hand to ground via either foot, through your heart. Current passing from your right hand to ground via your feet does NOT go through your heart meaning the current does not stop your heart from beating.. Current passing from the left hand to ground via your feet DOES go through your heart, stopping it from beating and hence stopping you from living

The thing is ... low voltage current (as in below 10000v or so) usually *does* travel through the heart whenever it gets the chance. Higher currents usually skip the heart. I can't remember why, but there was a very good explanation for this.

Oh and rubber gloves only help that much .. for a PSU they might be sufficient (I don't know what kind of charges those capacitators can hold), but I've seen a guy get fried when he wasn't even touching the power lines. Pretty darned scary how far (extremely high) currents can travel!

rubber gloves...

rubber gloves...

Re: rubber gloves...

Re: rubber gloves...