Capacitors in PSU are dangerous?

[Guest]

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On Mon, 19 Apr 2004 16:33:05 +0100, "half_pint"
<esboella.nospam@yahoo.com> wrote:

<snip>

>> >I guess it depends on the internal resistance of the capacitor, which is
>> >probably
>> >pretty negligible ( I have never ever seen it on a circuit diagram).
>>
>> Don't guess.
>
>Don't be so condesending.

Instead of guessing, do some research first. If I+V/R does that mean
there is nothing else to know about capacitors? No.


>You don't have a clue do you?
>Try inceasing your vocabulary to that of a 5 year old.


It seems as though you've taken to pulling something out of your ass
every 3rd post, something that would take more than a few lines to explain
till you realized why your guess was wrong. I'm not going to write a 500
word essay every time you can't be bothered to do some prerequisite
research/learning before making a "guess".

 

[gb]

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"beav AT wn DoT com DoT au" <"beav AT wn DoT com DoT au"> wrote in message
news:408336e7@quokka.wn.com.au...
> GB wrote:
> > Absolutely agree on the safety aspects. The only downside is that if
> there
> > is a significant charge left in the capacitor shorting it out may wreck
it.
> > Anybody have an idea of how likely that is with a fully charged large
> > capacitor?
>
> No idea (sorry) BUT someone earlier mentioned that they use a 240V 100w
> light globe and leads to discharge caps before use. This may be a safer
> way to go...
>

That seems an excellent way to do it. A decent-sized capacitor ( say 0.1
Farad) charged to 300 V has an energy content of the order of 5kJ. Unless my
arithmetic is wrong, that would keep a 100W light bulb lit for a couple of
minutes.

With that amount of energy stored, shorting it with a screwdriver would be a
bad idea. Assuming most of that energy would be consumed within the
capacitor, the average temperature would rise by say 50 degrees C. That
would not cause it any problems(?) However, I would also assume that there
would be a few hot spots (such as solder joints) where the temperature rise
would be much higher, and this would cause serious damage.

Anybody tried this?

Geoff

 

[gb]

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"half_pint" <esboella.nospam@yahoo.com> wrote in message
news:c5vfve$62bb5$2@ID-204080.news.uni-berlin.de...
>
> "beav AT wn DoT com DoT au" <"beav AT wn DoT com DoT au"> wrote in message
> news:408336e7@quokka.wn.com.au...
> > GB wrote:
> > > Absolutely agree on the safety aspects. The only downside is that if
> > there
> > > is a significant charge left in the capacitor shorting it out may
wreck
> it.
> > > Anybody have an idea of how likely that is with a fully charged large
> > > capacitor?
> >
> > No idea (sorry) BUT someone earlier mentioned that they use a 240V 100w
> > light globe and leads to discharge caps before use. This may be a safer
> > way to go...
>
> I guess it depends on the internal resistance of the capacitor, which is
> probably
> pretty negligible ( I have never ever seen it on a circuit diagram).
>
> Remember I=V/R and if the voltage on the cap is say 200V and the
> resistance is (choose a number) say one ohm then you have a current
> of 200 Amps!! even with 10 ohms you have 20 amps, probably enough to
> melt the connecting wires on the cap, never mind the microscopicly thin
> foild of its plates.
> Of course the internal resistance may well be much lower, fractions of
> an ohm, negligible, say its 0.01 ohms?
> Thats a current of 20 *thousand* amps.
>
> Maybe open up a cap and unwind it and try and measure the resistance
> from one end of the 'foil' to the terminal. It will probably regisiter as
> zero.
>
> Thats an infinite current!!
>
>

The internal resistance is very small, so the current would be large.
However, there is a limited amount of charge stored, so the current would
not last very long.

 

[Guest]

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"Ken" <___ken3@telia.com> wrote in message
news:u6c780hp3g4t1cihopoahr0f88bmgintms@4ax.com...
> On Sun, 18 Apr 2004 15:29:18 +0100, Michael Salem <a$-b$1@ms3.org.uk>
> wrote:
>
> >> All Europe use 230V today. UK adapted from 240V to 230V
> >> and the other countries from 220V to 230 volts.
> >
> > Nobody ACTUALLY changed their voltage, at least initially.
>
> In Sweden we did change from 220V to 230V a long time ago.
> Yes I could measure that on my volt meter.
> 230.5V on all 3 phases and 400V between the phases 5 minutes ago.

You have 3 phase domestic power supplies in Sweden?
>

 

[Guest]

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GB wrote:
> "beav AT wn DoT com DoT au" <"beav AT wn DoT com DoT au"> wrote in message
> news:408336e7@quokka.wn.com.au...
>
>>GB wrote:
>> > Absolutely agree on the safety aspects. The only downside is that if
>>there
>>
>>>is a significant charge left in the capacitor shorting it out may wreck
>
> it.
>
>>>Anybody have an idea of how likely that is with a fully charged large
>>>capacitor?
>>
>>No idea (sorry) BUT someone earlier mentioned that they use a 240V 100w
>>light globe and leads to discharge caps before use. This may be a safer
>>way to go..

I use an insulated lead with a 1W 10,000 ohm resiator in series with a
ground clip at one end and a long insulated probe at the other.

> That seems an excellent way to do it. A decent-sized capacitor ( say 0.1
> Farad) charged to 300 V has an energy content of the order of 5kJ. Unless my
> arithmetic is wrong, that would keep a 100W light bulb lit for a couple of
> minutes.

A 0.1 Farad at 300 V is more than a "decent sized" capacitor. For
example most PC PSUs contain two 470 mfd capacitors each charged to
about 160 V. The energy stored is 1/2 C E^2 = 1/2 470 x 10^-6 x 160 x160.
This is about 6 J or 12 J for the two. This would keep a 12 W bulb lit
for one second.
>
> With that amount of energy stored, shorting it with a screwdriver would be a
> bad idea. Assuming most of that energy would be consumed within the
> capacitor, the average temperature would rise by say 50 degrees C. That
> would not cause it any problems(?) However, I would also assume that there
> would be a few hot spots (such as solder joints) where the temperature rise
> would be much higher, and this would cause serious damage.
>
> Anybody tried this?

When I was designing megnetrons for high power RADAR, we used pretty
large capacitors charged to several kilivolts. This was sent to the
magnetron every RADAR pulse by way of a hydrogen thyratron. This produced
RF output pulses in the megawatt range. I never tried using a screw
driver to short anything. I have seen arcs that were pretty distructive.

Virg Wall
--

It is vain to do with more
what can be done with fewer.
William of Occam.

 

[Guest]

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kony wrote:
>
.... snip ...
>
> Power-on, charged voltage of cap (Rubycon 680mF) was 158V.
> Within a couple hours it had lost over half of it's charge, below
> 70V. Nearly 8 hours later it was below 10V and right now, 14 hours
> later, is at about 7.5V and draining so slowly that further
> measurement might better be made in days rather than hours.

Are you leaving the meter connected or just sampling? Most DVMs
have a constant input impedance of about 10 Meg. Multimeters can
be expected to have anywhere from 1k to 50k ohms per volt full
scale.

It all falls out of Ohms law and Q = CE.

--
Churchill and Bush can both be considered wartime leaders, just
as Secretariat and Mr Ed were both horses. - James Rhodes.

 

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kony wrote:

> On Thu, 15 Apr 2004 23:49:24 +0100, Tim Auton
> <tim.auton@uton.[groupSexWithoutTheY]> wrote:
>
>
>>>It's beyond overkill to advise waiting 24 hours. Even if you didn't know
>>>what you were doing you should've known that there's another very obvious
>>>way an ATX power supply drains besides the bleeder resistors.
>>
>>I'm assuming the worst case - ie component failure, where the only
>>discharge of the caps is self-discharge. In that case though, 24 hours
>>may not be enough. Hmmm, I think we need some experimental data.
>>
>>
>>Tim
>
>
> Well the data is a bit slow in coming but I did a sloppy test yesterday...
>
> I took a board from a power supply, that is quite typical, the basic
> filtering components between the AC socket and the rectifier, NOTHING
> after the rectifier... no bleeder resistors, no further power supply
> components at all beyond the rectifier By attaching the capacitor
> directly to rectifier output we would have an absolute worst case
> scenario, there is no way for the cap to drain slower than that no matter
> what else had failed in a power supply.
>
> Power-on, charged voltage of cap (Rubycon 680mF) was 158V.
> Within a couple hours it had lost over half of it's charge, below 70V.
> Nearly 8 hours later it was below 10V and right now, 14 hours later, is at
> about 7.5V and draining so slowly that further measurement might better be
> made in days rather than hours.

You're measuring the time constant of the internal, (parallel), resistance
of the capacitor. This can vary widely with the type of capacitor and even
its previous charge state. From a safety point of view its energy
content before its terminal voltage has dropped to a safe level may be more
important. In other words does its effective capacitance remain the same
during the whole of a self discharge cycle?
>
> Given that this was only a single cap and that I now have a better idea of
> time inteval for measurements, I may try another cap soon of higher
> capacity.

Do you know what value of capacitors are used in typical PSUs today? My
sample is limited to those with 470 mfd capacitors.

I made some measurements on a cheap L&C LC-235ATX supply. The CB inside
was marked "DEER", not one of the best quality makers.

Firstly, it was almost impossible to get even my finger tips on any
high, (DC), voltage points. The switching transistors were pretty
well protected by the insulated body of the input capacitors. I had to
remove four screws to get to the point under the CB to measure the
capacitor voltage.

I shorted pin 14 to ground and applied AC power. The unit started
without any exterior load and the output voltages were within normal
tolerances. The voltage across each 470 mfd capacitor was 162 V.
It dropped to essentially zero in about a second. Removing the ground
to cause the unit to not start, did not affect this behavior. As you
previously noted, the +5V SB did the same.

I did not remove the 220 ohm bleeders, but this time constant
is about 100 seconds. These bleeders are needed to equalize the
voltage between the input capacitors, so it's unlikely they'd be not used
to save costs. It seems the switching circuitry rapidly discharges the
capacitors, even when the supply is inactive.

I still urge everyone to use normal safety precautions, as with any
electrical device. The line power input terminals were exposed, so
it's important to be sure the unit is unplugged. No one without good
electrical experience should trouble shoot a PSU with applied voltage,
though it almost a necessity to do so to get meaningful results.

Repairs other than replacing the fan are probably not cost effective.

Virg Wall
--

It is vain to do with more
what can be done with fewer.
William of Occam.

 

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"kony" <spam@spam.com> wrote in message
news:qsu7809ol7gvo1v3f0dvb85nfceg3ph3dk@4ax.com...
> On Mon, 19 Apr 2004 16:33:05 +0100, "half_pint"
> <esboella.nospam@yahoo.com> wrote:
>
> <snip>
>
> >> >I guess it depends on the internal resistance of the capacitor, which
is
> >> >probably
> >> >pretty negligible ( I have never ever seen it on a circuit diagram).
> >>
> >> Don't guess.
> >
> >Don't be so condesending.
>
> Instead of guessing, do some research first. If I+V/R does that mean
> there is nothing else to know about capacitors? No.

Well obviously not there is other stuff to know, but
NOT ANYTHING WHICH IS RELEVANT.

So you are wrong.

>
>
> >You don't have a clue do you?
> >Try inceasing your vocabulary to that of a 5 year old.
>
>
> It seems as though you've taken to pulling something out of your ass
> every 3rd post, something that would take more than a few lines to explain
> till you realized why your guess was wrong. I'm not going to write a 500
> word essay every time you can't be bothered to do some prerequisite
> research/learning before making a "guess".


Well my "guess" is that you are either are retard or a troll, it more than
a "guess" though its more of a fact of life.

I you have something to say other than "your wrong" say it.
Otherwise just drag your posts directly to the recycle bin and save
me and everyone else the trouoble.

half_pint.
>
>

 

[Guest]

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"GB" <ThisIsNotMyEmailAddress@anywhere.intheuniverse> wrote in message
news:c60vld$idn$1@titan.btinternet.com...
>
> "half_pint" <esboella.nospam@yahoo.com> wrote in message
> news:c5vfve$62bb5$2@ID-204080.news.uni-berlin.de...
> >
> > "beav AT wn DoT com DoT au" <"beav AT wn DoT com DoT au"> wrote in
message
> > news:408336e7@quokka.wn.com.au...
> > > GB wrote:
> > > > Absolutely agree on the safety aspects. The only downside is that
if
> > > there
> > > > is a significant charge left in the capacitor shorting it out may
> wreck
> > it.
> > > > Anybody have an idea of how likely that is with a fully charged
large
> > > > capacitor?
> > >
> > > No idea (sorry) BUT someone earlier mentioned that they use a 240V
100w
> > > light globe and leads to discharge caps before use. This may be a
safer
> > > way to go...
> >
> > I guess it depends on the internal resistance of the capacitor, which is
> > probably
> > pretty negligible ( I have never ever seen it on a circuit diagram).
> >
> > Remember I=V/R and if the voltage on the cap is say 200V and the
> > resistance is (choose a number) say one ohm then you have a current
> > of 200 Amps!! even with 10 ohms you have 20 amps, probably enough to
> > melt the connecting wires on the cap, never mind the microscopicly thin
> > foild of its plates.
> > Of course the internal resistance may well be much lower, fractions of
> > an ohm, negligible, say its 0.01 ohms?
> > Thats a current of 20 *thousand* amps.
> >
> > Maybe open up a cap and unwind it and try and measure the resistance
> > from one end of the 'foil' to the terminal. It will probably regisiter
as
> > zero.
> >
> > Thats an infinite current!!
> >
> >
>
> The internal resistance is very small, so the current would be large.
> However, there is a limited amount of charge stored, so the current would
> not last very long.


True depending on the size of a capacitor, but obviously the big
ones can give you a nasty byte.

I forgot the capacitor equations (some time ago) so I wont try to work it
out.
>
>
>

 

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kony wrote:

> On Mon, 19 Apr 2004 16:33:05 +0100, "half_pint"
> <esboella.nospam@yahoo.com> wrote:
>
> <snip>
>
>>>>I guess it depends on the internal resistance of the capacitor, which is
>>>>probably
>>>>pretty negligible ( I have never ever seen it on a circuit diagram).
>>>
>>>Don't guess.
>>
>>Don't be so condesending.
>
>
> Instead of guessing, do some research first. If I+V/R does that mean
> there is nothing else to know about capacitors? No.
>
>
>
>>You don't have a clue do you?
>>Try inceasing your vocabulary to that of a 5 year old.
>
>
>
> It seems as though you've taken to pulling something out of your ass
> every 3rd post, something that would take more than a few lines to explain
> till you realized why your guess was wrong. I'm not going to write a 500
> word essay every time you can't be bothered to do some prerequisite
> research/learning before making a "guess".
>
>
He should change his name to "half_wit", but it still might be overstating
the capacity!

Virg Wall
--

It is vain to do with more
what can be done with fewer.
William of Occam.

 

[Guest]

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half_pint wrote:

> Bottom posting means you have to loads of unnecessary scrolling to real
> oneliner.

English translation?

 

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On Mon, 19 Apr 2004 17:56:34 GMT, CBFalconer <cbfalconer@yahoo.com> wrote:

>kony wrote:
>>
>... snip ...
>>
>> Power-on, charged voltage of cap (Rubycon 680mF) was 158V.
>> Within a couple hours it had lost over half of it's charge, below
>> 70V. Nearly 8 hours later it was below 10V and right now, 14 hours
>> later, is at about 7.5V and draining so slowly that further
>> measurement might better be made in days rather than hours.
>
>Are you leaving the meter connected or just sampling? Most DVMs
>have a constant input impedance of about 10 Meg. Multimeters can
>be expected to have anywhere from 1k to 50k ohms per volt full
>scale.
>
>It all falls out of Ohms law and Q = CE.

Just samping for a few seconds, though at the time I had forgotten about
it for a while, other work needed done, so I had no readings between 2 and
8 hour interval.

 

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kony <spam@spam.com> wrote:
>On Thu, 15 Apr 2004 23:49:24 +0100, Tim Auton
><tim.auton@uton.[groupSexWithoutTheY]> wrote:
[snip]
>>I'm assuming the worst case - ie component failure, where the only
>>discharge of the caps is self-discharge. In that case though, 24 hours
>>may not be enough. Hmmm, I think we need some experimental data.
>>
>Well the data is a bit slow in coming but I did a sloppy test yesterday...
>
>I took a board from a power supply, that is quite typical, the basic
>filtering components between the AC socket and the rectifier, NOTHING
>after the rectifier... no bleeder resistors, no further power supply
>components at all beyond the rectifier By attaching the capacitor
>directly to rectifier output we would have an absolute worst case
>scenario, there is no way for the cap to drain slower than that no matter
>what else had failed in a power supply.
>
>Power-on, charged voltage of cap (Rubycon 680mF) was 158V.
>Within a couple hours it had lost over half of it's charge, below 70V.
>Nearly 8 hours later it was below 10V and right now, 14 hours later, is at
>about 7.5V and draining so slowly that further measurement might better be
>made in days rather than hours.

Most interesting, thanks for the data.

I've a dead 400W ATX PSU lying around so I may duplicate your
experiment, but I've a telescope mount to reassemble before doing that
so don't hold your breath.


Tim
--
Love is a travelator.

 

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On Mon, 19 Apr 2004 11:26:12 -0700, "Timothy Daniels"
<TDaniels@NoSpamDot.com> wrote:

>
>"kony" wrote:
>> I took a board from a power supply, that is quite typical, the basic
>> filtering components between the AC socket and the rectifier, NOTHING
>> after the rectifier... no bleeder resistors, no further power supply
>> components at all beyond the rectifier By attaching the capacitor
>> directly to rectifier output we would have an absolute worst case
>> scenario, there is no way for the cap to drain slower than that no matter
>> what else had failed in a power supply.
>
>
> What about the reverse leakage current in the rectifier? Doesn't
>that amount to a bleeder resistor?
>
>*TimDaniels*

I suppose I could disconnect the rectifier and retest though the rectifier
is going to be in the theoretic power supply as a whole too, so it's
somewhat of a constant.

 

[gb]

Archived from groups: alt.comp.hardware,alt.comp.hardware.pc-homebuilt,uk.comp.homebuilt,alt.comp.hardware.homebuilt (More info?)

"VWWall" <vwall@DEADearthlink.net> wrote in message
news:4uUgc.2483$e4.2053@newsread2.news.pas.earthlink.net...
>
> Repairs other than replacing the fan are probably not cost effective.
>
> Virg Wall

The only PSU I had where the fan failed pretty much melted itself into a
heap of slag before the rest of it failed. It was only then that I found out
about the problem. Fortunately, it did not take anything else with it when
its soul went off to that great electronic warehouse in the sky.

 

[Guest]

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On Mon, 19 Apr 2004 18:01:36 GMT, VWWall <vwall@DEADearthlink.net> wrote:


>You're measuring the time constant of the internal, (parallel), resistance
>of the capacitor. This can vary widely with the type of capacitor and even
>its previous charge state. From a safety point of view its energy
>content before its terminal voltage has dropped to a safe level may be more
>important. In other words does its effective capacitance remain the same
>during the whole of a self discharge cycle?

Don't know and no capacitance meter here.


>Do you know what value of capacitors are used in typical PSUs today? My
>sample is limited to those with 470 mfd capacitors.

Depends a lot on make and wattage rating.
Typically the cheapies or lower wattage units, up to 250-300W, might be as
low as 220mF, but more commonly (perhaps most common) is 470-680, with
1000mF typically found only in some of the higher wattage models.

>I made some measurements on a cheap L&C LC-235ATX supply. The CB inside
>was marked "DEER", not one of the best quality makers.

Yep, I have some "guts" from a lot of those lying around, keep meaning to
throw them away but I might test one of those too, though I wasn't really
looking for a comprehensive analysis, just a rough idea of how long it'd
take to get under ~30V or so.


>Firstly, it was almost impossible to get even my finger tips on any
>high, (DC), voltage points. The switching transistors were pretty
>well protected by the insulated body of the input capacitors. I had to
>remove four screws to get to the point under the CB to measure the
>capacitor voltage.

True, though it seems likely that one of the heatsinks is HV still.

>I shorted pin 14 to ground and applied AC power. The unit started
>without any exterior load and the output voltages were within normal
>tolerances. The voltage across each 470 mfd capacitor was 162 V.
>It dropped to essentially zero in about a second. Removing the ground
>to cause the unit to not start, did not affect this behavior. As you
>previously noted, the +5V SB did the same.
>
>I did not remove the 220 ohm bleeders, but this time constant
>is about 100 seconds. These bleeders are needed to equalize the
>voltage between the input capacitors, so it's unlikely they'd be not used
>to save costs. It seems the switching circuitry rapidly discharges the
>capacitors, even when the supply is inactive.

I was considering just pulling the bleeders from a unit but already had
the misc parts I'd tried, lying out, "handy". Might get around to doing
that but it may be a while till I get a chance.

 

[Guest]

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"ric" asked:
> Timothy Daniels wrote:
>
> > > I took a board from a power supply, that is quite typical, the basic
> > > filtering components between the AC socket and the rectifier, NOTHING
> > > after the rectifier... no bleeder resistors, no further power supply
> > > components at all beyond the rectifier By attaching the capacitor
> > > directly to rectifier output we would have an absolute worst case
> > > scenario, there is no way for the cap to drain slower than that no matter
> > > what else had failed in a power supply.
> >
> > What about the reverse leakage current in the rectifier? Doesn't
> > that amount to a bleeder resistor?
>
> Current path would be...???

Backward through the rectifier. Besides being semi-conductors,
they're semi-insulators.

*TimDaniels*

 

[Guest]

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kony wrote:

> On Mon, 19 Apr 2004 18:01:36 GMT, VWWall <vwall@DEADearthlink.net> wrote:
>
>
>
>>You're measuring the time constant of the internal, (parallel), resistance
>>of the capacitor. This can vary widely with the type of capacitor and even
>>its previous charge state. From a safety point of view its energy
>>content before its terminal voltage has dropped to a safe level may be more
>>important. In other words does its effective capacitance remain the same
>>during the whole of a self discharge cycle?
>
>
> Don't know and no capacitance meter here.

I'm not sure how you could measure it even with one. Some way of measuring
stored energy after a time lapse might work.

As you know, electrolytic capacitors are complicated devices. The dielectric
is electro-chemically formed, and its resistance varies with temperature.
The input filters don't need especially low ESR, since line AC ripple doesn't
get through to the output filter capacitors where ESR is important.
>
>
>
>>Do you know what value of capacitors are used in typical PSUs today? My
>>sample is limited to those with 470 mfd capacitors.
>
>
> Depends a lot on make and wattage rating.
> Typically the cheapies or lower wattage units, up to 250-300W, might be as
> low as 220mF, but more commonly (perhaps most common) is 470-680, with
> 1000mF typically found only in some of the higher wattage models.
>
>
>>I made some measurements on a cheap L&C LC-235ATX supply. The CB inside
>>was marked "DEER", not one of the best quality makers.
>
>
> Yep, I have some "guts" from a lot of those lying around, keep meaning to
> throw them away but I might test one of those too, though I wasn't really
> looking for a comprehensive analysis, just a rough idea of how long it'd
> take to get under ~30V or so.
>
>
>
>>Firstly, it was almost impossible to get even my finger tips on any
>>high, (DC), voltage points. The switching transistors were pretty
>>well protected by the insulated body of the input capacitors. I had to
>>remove four screws to get to the point under the CB to measure the
>>capacitor voltage.
>
>
> True, though it seems likely that one of the heatsinks is HV still.

The input heatsink did show about - 280 V on a 20Kohm/volt meter. It
caused a (3 1/2 digit) DVM to wildly change indication. I found it was
left floating. Grounding it to the case didn't affect anything. Maybe
it was intentional to allow for a short on one the switching transistor's
insulation to the heatsink. I didn't try touching it! :-(
>
>
>>I shorted pin 14 to ground and applied AC power. The unit started
>>without any exterior load and the output voltages were within normal
>>tolerances. The voltage across each 470 mfd capacitor was 162 V.
>>It dropped to essentially zero in about a second. Removing the ground
>>to cause the unit to not start, did not affect this behavior. As you
>>previously noted, the +5V SB did the same.
>>
>>I did not remove the 220 ohm bleeders, but this time constant
>>is about 100 seconds. These bleeders are needed to equalize the
>>voltage between the input capacitors, so it's unlikely they'd be not used
>>to save costs. It seems the switching circuitry rapidly discharges the
>>capacitors, even when the supply is inactive.
>
>
> I was considering just pulling the bleeders from a unit but already had
> the misc parts I'd tried, lying out, "handy". Might get around to doing
> that but it may be a while till I get a chance.
>
>

Virg Wall
--

It is vain to do with more
what can be done with fewer.
William of Occam.

 

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Timothy Daniels wrote:

> > > What about the reverse leakage current in the rectifier? Doesn't
> > > that amount to a bleeder resistor?
> >
> > Current path would be...???
>
> Backward through the rectifier.

Fine, but where from there? The entire path. There isn't one.

 

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"ric" <nospam@home.com> wrote in message news:40844324.68C0742A@home.com...
> half_pint wrote:
>
> > Bottom posting means you have to loads of unnecessary scrolling to real
> > oneliner.
>
> English translation?

I am sure u can figure it out "read a" not "real"

 

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half_pint wrote:

|| Bottom posting means you have to loads of unnecessary scrolling to real
oneliner.

I guess that depends on whether you are using a proper newsreader program or
just any old e-mail client to read newsgroups.

Kevin.

 

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"Jim Howes" <sewoh.mij@moc.gisorp.backwards.invalid> wrote in message
news:c60r92$3il$1$8300dec7@news.demon.co.uk...
> Conor wrote:
>
> > Too true. Thats why you can stick your fingers in the HT lead hole in
> > the top of a monitor tube and just get an arm jolting belt. Sure its up
> > to 20,000 V but theres not alot of current.
>
> Err.. right..
>
> You first!

Would that be anything like the shock I got off a telly once? It was in
bits, but I wanted to get it back together enough to lump into the bin.
Couldn't get the case on properly, so decided to cut a very thick wire that
went onto the top of the tube. Figured plastic handled scissors would
insulate any shock, and it had been off and unplugged for at least a couple
of days.

Was quite a novel way to pop the main trip switch.

 

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Care to hazard a guess as to which newsreader 90% of users use?
You might win a coconut.
Need a clue? Click 'help' then 'about'.
It will even tell you your version number, your's is 6.00.2800.1106
by the way. :O|
About time you upgrade that old email client to the latest version?
You won't regret it :O|

half_pint.


"Kevin Lawton" <kepla@btinternet.com> wrote in message
news:c61nle$c5h$1@hercules.btinternet.com...
> half_pint wrote:
>
> || Bottom posting means you have to loads of unnecessary scrolling to real
> oneliner.
>
> I guess that depends on whether you are using a proper newsreader program
or
> just any old e-mail client to read newsgroups.
>
> Kevin.
>
>
>

 

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VWWall <vwall@DEADearthlink.net> wrote in message news:<4uUgc.2483$e4.2053@newsread2.news.pas.earthlink.net>...

> I did not remove the 220 ohm bleeders, but this time constant
> is about 100 seconds. These bleeders are needed to equalize
> the voltage between the input capacitors, so it's unlikely
> they'd be not used to save costs.

Inside my Enermax EV365P-VD (single-fan, 350W, included with an
Enermax CS-1251-B case), I couldn't find any bleeder resistors across
the high voltage 680uF capacitors or even empty spaces on the circuit
board where those resistors could have been installed. This is
probably a budget version Enermax because I saw another 350W Enermax
with 820uF capacitors, but I still don't understand why there were no
bleeders because I've seen them in even the cheapest PSUs, including

..
>
> I still urge everyone to use normal safety precautions, as with any
> electrical device. The line power input terminals were exposed, so
> it's important to be sure the unit is unplugged. No one without good
> electrical experience should trouble shoot a PSU with applied voltage,
> though it almost a necessity to do so to get meaningful results.
>
> Repairs other than replacing the fan are probably not cost effective.
>
> Virg Wall

 

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VWWall <vwall@DEADearthlink.net> wrote in message news:<4uUgc.2483$e4.2053@newsread2.news.pas.earthlink.net>...

> I did not remove the 220 ohm bleeders, but this time constant
> is about 100 seconds. These bleeders are needed to equalize
> the voltage between the input capacitors, so it's unlikely
> they'd be not used to save costs.

Inside my Enermax EV365P-VD (single-fan, 350W, included with an
Enermax CS-1251-B case), I couldn't find any bleeder resistors across
the high voltage 680uF capacitors or even empty spaces on the circuit
board where those resistors could have been installed. This is
probably a budget version Enermax because I saw another 350W Enermax
with 820uF capacitors, but I still don't understand why there were no
bleeders because I've seen them in even the cheapest PSUs, including a
300W MaxPower (Key Mouse) that could not have possibly met FCC
standards (no EMI filter, tons of AM radio noise). Should I solder an
approx. 200K resistor across each of those capacitors in the Enermax?

> I still urge everyone to use normal safety precautions, as with
> any electrical device. The line power input terminals were
> exposed, so it's important to be sure the unit is unplugged.
> No one without good electrical experience should trouble shoot
> a PSU with applied voltage, though it almost a necessity to do
> so to get meaningful results.

A friend of mine didn't believe me when I said that the heatsink for
the high voltage transistor(s) had 170VDC on it, but I showed him that
it did with Antec, Delta, and Powmax/Raidmax PSUs, and except for the
latter the transistors were insulated from those heatsinks. My
Enermax also has high voltage on its heatsink. No voltage on my
Fortron/Sparkle and Maxpower heatsinks, but nobody should assume that
this is always true.