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Old 8th March 2010, 11:06 PM
bearded fiddler bearded fiddler is offline
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Join Date: Jan 2009
Location: Tervuren, near Brussels, Belgium
Posts: 134
Default Re: Phono 3 with 5751 valves

Originally Posted by Richard View Post
Hi Jan,
Check the pic below carefully.
See the slightly protruding flat end of the white ceramic base.
See the brown mica disc with silver semi-circle that the screwhead is soldered to.
When the silver is turned to be fully at the flat end of the ceramic base that is max cap.
When the brown is at the flat end that is min cap.
When it is halfway with the screwslot aligned leg to leg it is half cap.
Thus, one complete turn of the screw will go from max through halfway to min then through halfway again and back to max. (So the full range is covered in half a turn of the screw, either way, and no end stop so no harm done.)
The full range measures 5-70pF.
The pic is set for 5751 at about 40pF (see the silver is more nearly at the flat end so is greater than half cap).
For Ecc83 you need about 20pF on this cap so wind it to a similar position but with the brown semicircle nearest the flat on the base to make less than half cap.
Hope this makes sense!

Hi Richard,

Thank you for your very prompt answer which makes a lot of sense in my opinion. There is a slight problem though: the Phono 3S parts list mentions a "5-50pF variable capacitor" for C9A/C10A. So the question is, what range have I got?

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