Capacitor keeps blowing

[budgie]

On Fri, 18 Feb 2005 08:18:18 GMT, "Brian Goldsmith" [SNIP]

So he is. Big deal, he could equally have been in the US of A where three
out
of every four pooter users think newsgroups starting with "aus" refer to
Austin
Texas.

Just because *we* are in Oz doesn't mean every poster is.

And if the above had been included in the original post, it would have
been
blatantly obvious even to blind freddy what the problem was.

Apparently not to the OP but who seems to have trouble understanding why a
device clearly marked "120VAC" shouldn't plug into "240VAC". Didn't they
pass a law about such people using electricity????????????????

No, but it seems like a good idea ...

 

[Kevin Ettery]

On Fri, 18 Feb 2005 08:18:18 GMT, "Brian Goldsmith" [SNIP]

So he is. Big deal, he could equally have been in the US of A where three
out
of every four pooter users think newsgroups starting with "aus" refer to
Austin
Texas.

Just because *we* are in Oz doesn't mean every poster is.

And if the above had been included in the original post, it would have
been
blatantly obvious even to blind freddy what the problem was.

Apparently not to the OP but who seems to have trouble understanding why a
device clearly marked "120VAC" shouldn't plug into "240VAC". Didn't they
pass a law about such people using electricity????????????????

No, just oxygen )

 

[Phil Allison]

"Martin"

Apparently not to the OP but who seems to have trouble understanding why a
device clearly marked "120VAC" shouldn't plug into "240VAC". Didn't they
pass a law about such people using electricity????????????????

** If you read all four posts from the OP it transpires he has a small,
iron transformer plug pack with *CONFLICTING* AC voltage labelling. The
unit has two *angled pins* that fit into an Aussie outlet and *NOT * a US
one. When plugged in, it produced a sensible reading of 32.7 volts on his
DC meter. A 10uF, 35 volt electro inside the equipment exploded when the
supply was used.

The only sensible explanation is that the particular plug pack is produces
unfiltered DC - typical of ones intended for battery charging duty.




.............. Phil

 

[Martin]

"Martin"


** If you read all four posts from the OP it transpires he has a small,
iron transformer plug pack with *CONFLICTING* AC voltage labelling. The
unit has two *angled pins* that fit into an Aussie outlet and *NOT * a US
one. When plugged in, it produced a sensible reading of 32.7 volts on his
DC meter. A 10uF, 35 volt electro inside the equipment exploded when the
supply was used.

The only sensible explanation is that the particular plug pack is produces
unfiltered DC - typical of ones intended for battery charging duty.




............. Phil

Yes, I read that later... Just goes to show that people really should learn
to include ALL the relevant info up front. As he did tell others that it
was 120VAC and then down the track mentioned "oh, it's 240VAC" just proves
that the OP's abilities are questionable... One wonders if he should be
trusted with a soldering iron? One also wonders if the plug pack polarity
was reversed hence the destruction of an electrolytic cap in the
equipment.... Doesn't seem that the voltage would've been enough to blow
that value cap like that, assuming that is we've been told accurate info and
don't find out down the track something different........ Unfiltered DC
wouldn't be enough to blow a cap like that - a capacitor is used to filter
DC, unless the plugpack is pumping out pure AC and not rectified unfiltered
DC at all... But he did, eventually, mention a 1000uF cap inside the plug
pack that has NOT blown so it must be rectified, (kind of) filtered DC.....
Back to polarity?????

 

[Pooh Bear]

I am really baffled now and need some Pro advise.

Plugged the AC charger in and it blew the capacitor

*what capacitor* ?

If you can't even explain that - then any other question is pointless.


Graham

 

[Phil Allison]

"Martin" <[email protected].

"Phil Allison"

Yes, I read that later... Just goes to show that people really should
learn to include ALL the relevant info up front. As he did tell others
that it was 120VAC and then down the track mentioned "oh, it's 240VAC"
just proves that the OP's abilities are questionable... One wonders if he
should be trusted with a soldering iron?

** I could say that about half the repair techs in Sydney ........

One also wonders if the plug pack polarity was reversed hence the
destruction of an electrolytic cap in the equipment.... Doesn't seem that
the voltage would've been enough to blow that value cap like that,
assuming that is we've been told accurate info and don't find out down the
track something different........

** The peak voltage was easily enough if the plug pack was delivering
unfiltered DC.

Unfiltered DC wouldn't be enough to blow a cap like that ...

** WRONG !

Read all my posts in this thread - the *peak* value of full wave rectified
AC is 57% higher than the average value as read on a DC meter.

PLUS - a filter cap of only 10uF operating with a load of 100 mA (at 100
Hz ) in a insufficient filter. The cap will have a very high peak to peak
ripple voltage, likely the same as the DC supply voltage and a ripple
current more than it can tolerate even if the voltage rating is not
exceeded.

Remember the formula: C = I dv/dt ???

Transposing gives: dv = I dt / C

So for 1 = 0.1 ; dt = 8mS and C = 10 uF gives dv = 80 volts !!

So the output voltage from the supply will drop to very near zero 100 times
per second despite the filter cap !!!!



- a capacitor is used to filter

DC, unless the plugpack is pumping out pure AC and not rectified
unfiltered DC at all...

** See above - the cap is too small to be a filter for 100mA.

The minimum value needed is 100 uF making the ripple voltage 8 volts p-p.

But he did, eventually, mention a 1000uF cap inside the plug pack that has
NOT blown so it must be rectified, (kind of) filtered DC.....

** That was another and DIFFERENT plug pack.

Back to polarity?????

** Doubt it.



................. Phil

 

[[email protected]]

I just looked at the polarity question here,on the supply in question
it WAS reversed,I did not reverse it,it looked like a fixed connection
to me.Possibly reversed by accident,by whoever touched it before I got
it.It had Manufacture Sticker on the supply,so what could go wrong so
to speak.
It is NOT the original power supply all the same,possibly it did work
and is filtered,hence it came with the item.
I made dam sure the polarity was correct when attaching the Danar Power
supply,checked twice then double checked I assure all.

Thanks again your input the item functions perfectly after a long
charge