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  #11  
Old 15th February 2017, 12:08 PM
John Caswell John Caswell is offline
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Default Re: Valve Data confusion.

Hi all,
As the cathode of the top valve is is elevated "X" volts above earth and possibly the heaters are earthed, it would be a good idea to elevate the heaters so that you do not exceed the mfrs heater cathode rating. I suggest halfway between the upper cathode voltage and the lower cathode voltage, implemented like the Phono II/ III. Remember to decouple it with a suitably rated elco capacitor

John
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  #12  
Old 15th February 2017, 12:11 PM
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pre65 pre65 is offline
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Default Re: Valve Data confusion.

Bob, has the heater transformer got a centre tap ?
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  #13  
Old 15th February 2017, 12:20 PM
bob orbell bob orbell is offline
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Default Re: Valve Data confusion.

Quote:
Originally Posted by pre65 View Post
The MJ article does not mention raised heater potential.

Are your heaters raised potential Bob ?
Yes Philip they are, I am using two WD PSU III's one for the Phono @ 250 and one for the Pre @ 285 so both have elevated heater supply's. BOB
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  #14  
Old 15th February 2017, 12:23 PM
bob orbell bob orbell is offline
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Default Re: Valve Data confusion.

Thank you all for your comments, John,Philip, see my post no. 13. BOB
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  #15  
Old 15th February 2017, 12:24 PM
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pre65 pre65 is offline
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Default Re: Valve Data confusion.

I can't remember what volts were added to lift the heaters on the Pre3, is it enough ?
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  #16  
Old 15th February 2017, 12:31 PM
bob orbell bob orbell is offline
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Default Re: Valve Data confusion.

Yes Philip it is, the cathode will sit about 200v above ground, I think all the information about that is in the FAQ, Pre II conversion to CF. BOB
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