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jharasym
 Post subject: Close, but no cigar yet
PostPosted: Sat Mar 05, 2011 12:22 pm 
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Going through the power up, got to the point of installing tubes and measuring DC at the second 50 µf cap + terminal. With VRM at idle I get 440.5 VDC (120.1 VAC supply). When I turn the VRM up, the voltage drops rather than rising, to 395 at max VRM.

The wiring of the VRM pot looks OK according to the layout.

Suggestions?
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kurtlives
PostPosted: Sat Mar 05, 2011 12:25 pm 
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Measure the voltage as you turn the VRM at the first filter cap. It should vary there from (sub 100V) to around 400V.

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jharasym
PostPosted: Sat Mar 05, 2011 12:33 pm 
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That looks better - I get 392 VDC at max VRM. Good to go to the next step?
Thanks
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kurtlives
PostPosted: Sat Mar 05, 2011 12:43 pm 
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Sounds good,
on to the next step.

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jharasym
PostPosted: Sat Mar 05, 2011 12:46 pm 
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Cool.
I'm not seeing where to measure B+ in the next step. The build manual says to measure at the 50 µf cap R8/C6 connection. Could you point me at this connection?
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zaphod
PostPosted: Sun Mar 06, 2011 1:02 am 
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You measure (real carefully) at the positive terminal of that cap - ie the terminal that isn't connected to ground.

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