Values of caps in a voltage quadrupler?

[Shiva]

Here's the thing - i have a 7amp isolation doughnut, and would like to turn
it into a HT power supply. What would i need for caps? I what are the
drawbacks? This is goin' to go through pass regulators ( a bunch of 6l6's
or something), so ripple is not that important to me. R out & amperage
is...
-dim

[Tim Williams]

I'd guess you'll only be drawing 200mA from it so 1A would be enough,
so you're 6A over a safe level in that regard. :) As for the caps, I
think you want to consider it as the long string from + to - as one
cap, so if you want 200uF on the output, you need 4x800uF caps. But
they can be 160V.

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

"Shiva" > wrote in message
...
> Here's the thing - i have a 7amp isolation doughnut, and would like to
turn
> it into a HT power supply. What would i need for caps? I what are the
> drawbacks? This is goin' to go through pass regulators ( a bunch of 6l6's
> or something), so ripple is not that important to me. R out & amperage
> is...
> -dim
>
>

[John Byrns]

In article >, "Tim Williams"
> wrote:

> I'd guess you'll only be drawing 200mA from it so 1A would be enough,
> so you're 6A over a safe level in that regard. :) As for the caps, I
> think you want to consider it as the long string from + to - as one
> cap, so if you want 200uF on the output, you need 4x800uF caps. But
> they can be 160V.

Careful there, he didn't say what input Voltage he is starting with, and
even if it is only 120 VAC I don't think all the capacitors can be 160V,
the exact requirements would depend on the particular "quadrupler"
topology choosen, there are several.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/

[Gregg]

Behold, Shiva scribed:


> So, instead of trial & error, how would I go 'bout figurin' out what I
> need? Motor start caps? Pricy, kind'o. I've never tried a high-amp
> quadrupler, just wondering where to start. -dim

Computer grade caps, as well as photoflash caps are good at dumping large
amounts of current. Photo-flash caps have a high-Z, so paralleling them
with a computer grade cap would be what I'd do. Also parallel a 0.1uF
mylar puppy in there to bypass the high-freq's that cause inductive
troubles in the big caps.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*

[Shiva]

"Gregg" > wrote in message
. ..
> Behold, Shiva scribed:
>
>
> > So, instead of trial & error, how would I go 'bout figurin' out what I
> > need? Motor start caps? Pricy, kind'o. I've never tried a high-amp
> > quadrupler, just wondering where to start. -dim
>
> Computer grade caps, as well as photoflash caps are good at dumping large
> amounts of current. Photo-flash caps have a high-Z, so paralleling them
> with a computer grade cap would be what I'd do. Also parallel a 0.1uF
> mylar puppy in there to bypass the high-freq's that cause inductive
> troubles in the big caps.
>
> --
> Gregg
> *It's probably useful, even if it can't be SPICE'd*

Thanks - makes sense. What exactly are computer - grade caps (embarrasing
question #456)? Is it basically the caps I pull out of switcher power
supplies? But those seemto be all over the field too, and a fiend of mine
(half sarcastically, half seriously), claims that he's resorted to judging
the 'lytic caps by their sieze, which almost makes sense...if you have a
small cap with a high value,it implies that they're using real thin
aluminum, scored or pitted to increase the surface area. I've actually been
told by an old-timer to never discharge those things without a resistor, or
the cap'll do one of those unpleasant exploadin' things. Also makes sense.
Am I way off?
-dim

[Tim Williams]

"John Byrns" > wrote in message
...
> > I'd guess you'll only be drawing 200mA from it so 1A would be enough,
> > so you're 6A over a safe level in that regard. :) As for the caps, I
> > think you want to consider it as the long string from + to - as one
> > cap, so if you want 200uF on the output, you need 4x800uF caps. But
> > they can be 160V.
>
> Careful there, he didn't say what input Voltage he is starting with, and
> even if it is only 120 VAC I don't think all the capacitors can be 160V,
> the exact requirements would depend on the particular "quadrupler"
> topology choosen, there are several.

That's true. But he said isolation transformer and being in NY he
has 120V so 120V out. So ya might need some 350V caps ;)

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

[Shiva]

"Gregg" > wrote in message
. ..
> Behold, Shiva flashed in code from a keyed 4-1000A filament:
>
>
> > "Gregg" > wrote in message
> > . ..
> >> Behold, Shiva scribed:
> >>
> >>
> >> > So, instead of trial & error, how would I go 'bout figurin' out what
> >> > I need? Motor start caps? Pricy, kind'o. I've never tried a
> >> > high-amp quadrupler, just wondering where to start. -dim
> >>
> >> Computer grade caps, as well as photoflash caps are good at dumping
> >> large amounts of current. Photo-flash caps have a high-Z, so
> >> paralleling them with a computer grade cap would be what I'd do. Also
> >> parallel a 0.1uF mylar puppy in there to bypass the high-freq's that
> >> cause inductive troubles in the big caps.
> >>
> >> --
> >> Gregg
> >> *It's probably useful, even if it can't be SPICE'd*
> >
> > Thanks - makes sense. What exactly are computer - grade caps
> > (embarrasing question #456)? Is it basically the caps I pull out of
> > switcher power supplies? But those seemto be all over the field too,
> > and a fiend of mine (half sarcastically, half seriously), claims that
> > he's resorted to judging the 'lytic caps by their sieze, which almost
> > makes sense...if you have a small cap with a high value,it implies that
> > they're using real thin aluminum, scored or pitted to increase the
> > surface area. I've actually been told by an old-timer to never
> > discharge those things without a resistor, or the cap'll do one of those
> > unpleasant exploadin' things. Also makes sense. Am I way off? -dim
>
> I wouldn't be able to tell you if that's true or not, as I have not
> researched that.
>
> Switcher caps have low inductance, therefore low series-Z. Leakage can be
> rather high compared to ordinary 'lytics.
>
> It seems to me that their foil can't be too thin, because they have a huge
> current reserve - up to 10X a bypass or coupling cap of the same value.
>
> They are available in voltages up to 500V @ 2,500uF capacitance too -
> probably just what you need.
>
> My local surplus store has a bin full of 6.3V, 2.2F (yes, Farad) for $10
> a pop, as well as 6,800uF 200V ones for the same price.
>

Yeah, I picked up a whole bag of 300 by 360V caps, at .50 a piece, at the
last swap I went to - they're about the size of 1/2 of a AA bat. Really
confusing. I just don't understand how such a thing is possible. Maybe
something different from aluminum, and some sort of newfangled electrolite?
Some mono-molecular film they form on the foil which is a killer insulator?
There must be some new technology that we don't know... Would be fun to
find out - i have a can that I got from the same guy that's also rated at
360V, and it's something like 20,000... Weirdness...
-dim

[Shiva]

"RetroTeckh" > wrote in message
...
> >From: "Shiva"
> >Date: 8/2/03 12:42 PM Eastern Daylight Time
> >Message-id: >
> >
> >Here's the thing - i have a 7amp isolation doughnut,
>
> Toroids cannot tolerate a DC condition. Make sure that the
circiut
> draws an AC current.
>

Good point - i haven't thought of that, since the primary is always
swingin', but now that I think about it, I guess there are topologies which
will cause a DC condition... Thanks.

>
> and would like to turn
> >it into a HT power supply. What would i need for caps?
>
> The bigger, the better, the tighter the sweater.
>

As long as we're talkin' about caps... Otherwise I disagree with the first
part...

> I what are the
> >drawbacks? This is goin' to go through pass regulators ( a bunch of
6l6's
> >or something)
>
> Use EL34's because they can tolerate up to 800 volts.
> 120volts X 5.6 =672volt DC.
>

You know, i run 6L6's at 800V all the time, and other than the base arc -
over, they hold up. Big names like Ampeg also use(d) 6L6's way past their
voltage rating - all's well. If i was building a chassis for this, i'd
probably go with sometrhing like a bunch of 807's, but they simply wouldn't
fit here. 6550's are almost kissin' each other... but pin one is not used,
i'll jump it & try...

> , so ripple is not that important to me. R out & amperage
> >is...
>
>
> It may be more practical to use several LM317T chips because
> each one can handle 1.5 amps but the maximum voltage drop is
> only 40 volts. OK, maybe alot of them.
>

Err... I know the suckers float, but i also know that I blew up (actually,
the T's don't blow up, they die quietly) a bunch of them. If it was
something to "build & leave alone", then, maybe... Besides, I'd feel
foolish with all the voltage ref. tubes glowin' in different colors,
lightin' up a bunch of transistors... Anyhow, I'm afraid of 317's as
high-voltage floaters... If i was more careful...
-dim
>
> >-dim
>
>
>

[Fred Nachbaur]

Shiva wrote:
> "RetroTeckh" > wrote in message
> ...
>
>>>From: "Shiva"
>>>Date: 8/2/03 12:42 PM Eastern Daylight Time
>>>Message-id: >
>>>
>>>Here's the thing - i have a 7amp isolation doughnut,
>>
>> Toroids cannot tolerate a DC condition. Make sure that the
>
> circiut
>
>>draws an AC current.
>>
>
>
> Good point - i haven't thought of that, since the primary is always
> swingin', but now that I think about it, I guess there are topologies which
> will cause a DC condition... Thanks.
>
>

The topology shown here
http://www.dogstar.dantimax.dk/tubestuf/graphics/tt42ps.gif is
symmetrical, and won't have a DC component in the secondary. Note that
the secondary voltage in this particular circuit is only about 50 volts,
so for your circuit you'd have to insure that the capacitors are rated
higher. C1 and C2 could be as low as 160v, C3 and C4 would be 350v, and
C5/C6 should be able to tolerate at least 650 volts.

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

[John Byrns]

In article >, Fred Nachbaur
> wrote:

> Shiva wrote:
> > "RetroTeckh" > wrote in message
> > ...
> >
> >>>From: "Shiva"
> >>>Date: 8/2/03 12:42 PM Eastern Daylight Time
> >>>Message-id: >
> >>>
> >>>Here's the thing - i have a 7amp isolation doughnut,
> >>
> >> Toroids cannot tolerate a DC condition. Make sure that the
> >
> > circiut
> >
> >>draws an AC current.
> >>
> >
> >
> > Good point - i haven't thought of that, since the primary is always
> > swingin', but now that I think about it, I guess there are topologies which
> > will cause a DC condition... Thanks.
> >
> >
>
> The topology shown here
> http://www.dogstar.dantimax.dk/tubestuf/graphics/tt42ps.gif is
> symmetrical, and won't have a DC component in the secondary.


Worse than that, even if it weren't symmetrical, it still couldn't draw
any DC current with the capacitors at the input.


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/