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Old 17th February 2009, 10:54 AM   #2961
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by AndrewT
could somebody be more specific.
I went back 5pages ........

Quote:
Originally posted by Zen Mod



go back to FIRST 5 or 6 pages
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Old 17th February 2009, 10:56 AM   #2962
AndrewT is offline AndrewT  Scotland
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oops, I've just gone back through 960 posts.
Now I'll start at the beginning.
Why don't they send me back to school and teach me to read!
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Old 17th February 2009, 02:44 PM   #2963
meemee is offline meemee  Indonesia
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Default Re: Re: Re: Re: newbie need help

Quote:
Originally posted by labjr


That's 8-10 amps per winding. You're going to need a transformer that is capable of twice that at 16 to 20 amps.




woooooowww.......toroid 16A or 20A. how much it cost in your country??

is there someone from singapore, ausey or new zealand (they're the close one).
if i buy this toroid and send to my country indonesia, who much it cost?? (toroid+shipping)

thank you.
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Old 17th February 2009, 02:44 PM   #2964
meemee is offline meemee  Indonesia
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Default Re: Re: Re: Re: newbie need help

Quote:
Originally posted by labjr


That's 8-10 amps per winding. You're going to need a transformer that is capable of twice that at 16 to 20 amps.




woooooowww.......toroid 16A or 20A. how much it cost in your country??

is there someone from singapore, ausey or new zealand (they're the close one).
if i buy this toroid (220V/18-0-18/20A)and send to my country indonesia, who much it cost?? (toroid+shipping)

thank you.
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Old 17th February 2009, 03:14 PM   #2965
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Default Re: Re: Re: Re: Re: newbie need help

Quote:
Originally posted by meemee
......toroid 16A or 20A. how much it cost in your country??

is there someone from singapore, ausey or new zealand (they're the close one).
if i buy this toroid (220V/18-0-18/20A)and send to my country indonesia, who much it cost?? (toroid+shipping)

thank you.
John at Antek sends them via Global Priority Mail "Flat Rate Box" -- they've upped the price recently, but you can fit 20# (9kg) for $42 almost anywhere in the world.
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Old 17th February 2009, 07:51 PM   #2966
udailey is offline udailey  United States
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I just talked to a guy at Wakefield. He says that those microfins on the heatsinks regular fins dont come into play in natural convection AT ALL. Not in any way are they considered part of the total surface area. He says they need 600LFM or was it CFM, anyway they need a lot of air before they are an advantage.
Uriah
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Old 17th February 2009, 09:59 PM   #2967
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That's mostly the case. Plus, they are dust collectors.

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Old 17th February 2009, 11:41 PM   #2968
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Default zen5 (for F5) power supply with V reg - need help

Hi all,

The AC voltage at my house varies quite a bit (114V RMS ot 126V RMS). And the rail
voltage and DC offset on my (diy) F5 varies with it. So I thought I would try modifying
my Zen5 based power supply to use feedback and see if that gave me more stable
rail voltage.

My plan was to use LM317/LM337 IC adjustable voltage regulators in place of the zener
diodes to control the mosfets used for regulation. I've included a diagram of the circuit
for the positive side.

My problem is that at best, my regulated output voltage is about 10V less than my
unregulated voltage. I'm sure I've done something wrong, but I can't see it. Would
anyone care to offer any help or insight?

Again, this circuit is (was) the Zen 5 power supply. I have not shown the parts before
the inductor coils, as it is the same as the Zen 5. In my case, I get about 28V. The
max voltage I get after the LM317 is 18V.

There is a lot that I don't understand about this (and the stock) supply. I think the
1K resistor is a current limiting resitor for the (removed) zender diodes. As this part
of the circuit doesn't use much current, it seemed reasonable to keep them. Nelson
mentions that the diodes are to quickly drain the 2200uF caps, but I don't understand
how they do that. I guess they also somehow act as flyback diodes for the coils too
(and I don't understand that either), so I decided to keep them. I think the diode on
the input side of the regulator is for flyback purposes, and the diode on the output side
of the regulator is to drain the 2200uF caps.

The LM317 requires a current load of at least 3.5mA, The 2.6K resistor was supposed
to supply that (when at 26V).

Could someone please give me a hand with this?

thanks,
Robert
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Old 18th February 2009, 12:12 AM   #2969
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Why not just replace the 1k resistor with constent current source
diode or jfet? Sure would be a lot easier.
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Old 18th February 2009, 01:00 AM   #2970
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Default Re: zen5 (for F5) power supply with V reg - need help

Quote:
Originally posted by audiorob

In my case, I get about 28V. The
max voltage I get after the LM317 is 18V.


It seems that 1k and 2.6K are acting as a voltage divider.
That is the "in" voltage of LM317 seems to be only about 28*2.6/3.6= 20V.


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