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Old 24th June 2009, 05:50 PM   #11
panos29 is offline panos29  Greece
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This preregulation circuit never worked correct for me too. On top of that after some minutes under load the toroidal gets very warm as presumably there is alot of DC going to the transformer through the stupid dimmer(preregulator). Never got around fixing it although I really spent alot of hours on this.
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Old 26th June 2009, 10:48 AM   #12
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Quote:
Originally posted by smithy666
Rick
Sorry, the sound is almost like a cross between ticking and buzzing. It's not like a transformer humming under a large load, but has a more distinctive tick/buzz at a quite a fast repetition, which gets louder as the load increases.
I have an 8R load, which at approx 35V & 4.5A still makes the same noise. I would need to hook up another load to test 1-2A at max voltage.
On the CRO photos, the last 2 are measured between the common side of R29 (CRO ground) and the L1 side of R34 (can't easily connect to other isde of inductor).
The first photos I posted were with one connection only from the CRO to the L1 side of R34 (ground of the CRO probe wasn't connected). Does this help?
thanks
Chris

Isn't the ticking to be expected with a phase-control prereg? Halfway through the cycle the load is connected/disconnected and the transformer mechanically reacts on it. It should be 100 Hz period, and increase in level (I suspect) with higher load currents and/or higher input/output differentials ( lower Vout).
But if it works, nothing to worry about.

Jan Didden
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Old 17th July 2009, 03:46 PM   #13
yeti is offline yeti  Germany
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In my younger years i worked for a small firm that did lighting for discos and events. The noise you describe is like the noise from dimmer racks connected to spots at 1KW or more. The steep rising of the current after triac turn on causes a reaction force that lets the copper wires get the jitters. One possibility to reduce this is to dive the transformer into some kind of epoxy resin and bake it. The other is probably a L-C filter as it is used in the output of a dimmer circuit. My suggestion is a suppression coil (say 10...20 mH) in series between the triac and the transformer and a capacitor (0.1 uF mkp) parallel to the transformer. Maybe you must fiddle a bit with the values, but it should improve things.

Arne
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Old 11th July 2010, 07:41 AM   #14
aubunnz is offline aubunnz  New Zealand
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smithy666;

Could you please send me the schematic for the Elektor Lab supply your link for the PS Schematic is not working?

Thank you

Aubunnz
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Old 12th October 2010, 05:35 AM   #15
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Quote:
Originally Posted by janneman View Post
Isn't the ticking to be expected with a phase-control prereg? Halfway through the cycle the load is connected/disconnected and the transformer mechanically reacts on it. It should be 100 Hz period, and increase in level (I suspect) with higher load currents and/or higher input/output differentials ( lower Vout).
But if it works, nothing to worry about.

Jan Didden
Jan, you are correct on the noise...it does increase with increased current. The supply works fine, it's just an annoying noise, but I would have thought when Elektor designed it they would have also noticed the noise and made a comment about it.

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Old 13th October 2010, 05:35 AM   #16
aubunnz is offline aubunnz  New Zealand
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Thank you for the new link your assistance is appreciated

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