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Old 21st November 2013, 03:48 AM   #2541
Salas is online now Salas  Greece
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It was half a lucky shot because I don't know what else can be at play when something is not examined on my bench also. But you were doing the correct experiments and we found a way.
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Old 21st November 2013, 05:50 AM   #2542
stajo is online now stajo  Sweden
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Stajo will advise you on that, who has a stash of chokes to check out. Me I said use a cmult cascade at the output.
Sorry I was too late, but hey congrats, you solved it.

To make an after analyze, I would do a voltage check before and after the 317. It should kill your ripple better. Do you really have sufficient vdrop concerning both amps and temp in the datasheet? To that you must add at least the ripple level (PP/2 I think, not sure) before the 317.
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Old 21st November 2013, 07:52 AM   #2543
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Hello,

I use BJT kit and set 600mA CCS (440mA load) for Buffalo IIISE . Can I use all red LEDS (D102,D103,D104,D105,D106) ? .

Thank you.

Van Duy
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Old 21st November 2013, 08:03 AM   #2544
Salas is online now Salas  Greece
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If they give 1.9V at 2-3mA yes. Test one with suitable resistor and voltage to verify forward voltage drop at such current levels.
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Old 21st November 2013, 02:27 PM   #2545
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Originally Posted by stajo View Post
Sorry I was too late, but hey congrats, you solved it.

To make an after analyze, I would do a voltage check before and after the 317. It should kill your ripple better. Do you really have sufficient vdrop concerning both amps and temp in the datasheet? To that you must add at least the ripple level (PP/2 I think, not sure) before the 317.
My voltage before 317 was 19.3v from Raw DC when amp connected. After 317, 13.8v stable. No heat on sink (about 30 deg C constantly).
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Old 21st November 2013, 02:49 PM   #2546
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Thank Salas for your quick reply ,

With +- 15VDC for Legato, Can I replace Q104, Q204 (BC550, BC560) by BC548B, BC558B ?.
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Last edited by nvduybom; 21st November 2013 at 02:58 PM.
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Old 21st November 2013, 03:13 PM   #2547
stajo is online now stajo  Sweden
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My voltage before 317 was 19.3v from Raw DC when amp connected. After 317, 13.8v stable. No heat on sink (about 30 deg C constantly).
That should be fully satisfactory for it to bring home the bacon. A wild guess that you have between 0,7 and 1,0 vrms ripple before it and it should have no problem with bringing down that with 60-80 dB.

Harsh spikes from rectification tho can be another story. But now you have a working PSU to enjoy.

PS. My earlyer comments about voltage before and after choke assumed that the choke was first thing after rectification. On later pix I saw that was not the fact, so that can be ignored.

Last edited by stajo; 21st November 2013 at 03:17 PM.
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Old 21st November 2013, 05:51 PM   #2548
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That should be fully satisfactory for it to bring home the bacon. A wild guess that you have between 0,7 and 1,0 vrms ripple before it and it should have no problem with bringing down that with 60-80 dB.

Harsh spikes from rectification tho can be another story. But now you have a working PSU to enjoy.

PS. My earlyer comments about voltage before and after choke assumed that the choke was first thing after rectification. On later pix I saw that was not the fact, so that can be ignored.
I'm fully satisfied (thanks to Salas) , but any way if you will use choke setup there (alternative way to emiter capmult) , then what values of choke would you suggest for such circuit?
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Old 21st November 2013, 08:02 PM   #2549
Salas is online now Salas  Greece
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Originally Posted by nvduybom View Post
Thank Salas for your quick reply ,

With +- 15VDC for Legato, Can I replace Q104, Q204 (BC550, BC560) by BC548B, BC558B ?.
Better not because they have worse noise figure spec.
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Old 21st November 2013, 10:58 PM   #2550
stajo is online now stajo  Sweden
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I'm fully satisfied (thanks to Salas) , but any way if you will use choke setup there (alternative way to emiter capmult) , then what values of choke would you suggest for such circuit?
Well chokes in series is like everything else, ohms law. If your current is I=U/R=12/500 (bleeder) you have 24 mA to deal with and you just find a choke that takes the limit. Add the current of your devise and maybe 50 mA is a good one in your case. If you, like I first thought, use the choke as first element (L-C) in a filter chain, it has to deal with much larger ripple, and my approach is to at least double the current spec.

What comes up is: When you use a cap, large enough, as first devise, the voltage after rectification will be AC x sqr2 minus the voltage drop over each rectifier diode. In a greatz bridge its two diodes so its (AC x 1,41) minus (vdrop x 2. In your case (14 x 1,41) - (0,7 x 2) = 18,3 volt.

If you, on the other hand, puts the choke as first device, you will only get AC x 0,9 volts minus vdrop on diodes. You might win that some spikes from the rectifications that not gets enhanced by the first cap and further into the circuit.

It takes more voltage to start with tho. In tube circuits, where you might want 3-500 volts, it might be encumbering to make an L-C. In low voltage circuits tho, if you find good availiable chokes, its my first choce.

My fav circuits in tube circuits is usually a middle way: small cap-small inductor etc. You can set the voltage with the size of the first cap, and your noice pollution will be minimal.
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