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Old 1st March 2011, 07:27 PM   #31
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Hi George, The layout is tight but I can see what I can do... Might breadboard it before putting it on the verro board! A breadboard is another thing in the shopping basket along with the resistors The 10,000uF caps are pretty big.... even 4700uF though should be more than enough don't you think I guess actual measurements will be the acid test.

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Old 1st March 2011, 11:30 PM   #32
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Quote:
Originally Posted by gpapag View Post
I broke the ceramic housing and measured the dimentions of one of the coiled resistors:
Coilís Diameter: 3.7mm
Coilís Length: 7.0mm
Wireís diameter: 0.02mm
Number of turns: 12

Calculated L=0.3uH due to geometry, independent of frequency.
The frequency dependent Inductance is up to 500MHz another 0.3uH, so the total calculated L= 0.6uH.
Why such a big difference btn measured and calculated?
Probably due to the end cups and leads which are magnetic?
Do you know the measurement frequency of your LC meter? It certainly could be that the end caps and steel leads are acting in some way like a high mu core for the coil, even though they're outside it. But the increase seems really dramatic.

Quote:
So, taking the highest inductance of the two (L=12uH) what can the HF roll-off be?
Like DF96 says, not really significant in the audio band for a value of 12uH. The leakage inductance of your transformer will almost certainly swamp this by a few orders of magnitude (mine measured around 4mH). If it were a toroidal the leakage inductance would be lower but still considerably higher than 12uH. I think its safe to consider them just resistors in the present context.
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Old 2nd March 2011, 08:33 AM   #33
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16uh wont do much in the audio band, it will only attenuate frequenties far outside the audio spectrum. However it does introduce a small phase shift not sure if it does any harm.
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Old 2nd March 2011, 10:36 AM   #34
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Post30 shows the results of research.
The regulator has a sensor circuit and a regulated output.
One must "layout" the 3pin reg such that it can do both jobs properly.
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Old 2nd March 2011, 11:47 AM   #35
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12uH and 4.7R have the same impedance at 62kHz, so not much effect at audio frequencies. Treat them as pure resistors in a PSU. You might have to consider inductance if they are used in the signal handling part, but even then marginal.
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Old 11th May 2011, 10:21 PM   #36
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Hi George, I've done some measurements using your technique. initial results posted here --> Power Supply Questions

Tony.
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Old 12th May 2011, 09:21 PM   #37
gpapag is online now gpapag  Greece
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Excellent Tony.

Thanks for notifying me.

Regards
George
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