bugeyes wrote:
I hope this question isn't too naive, but I had a question about the B+ supply to the pre-amp tube. On your build do you have two leads coming from the 470k resistor to supply the 250volts?
Not a naive question at all. The short answer is yes. But the full answer is a little more complicated.
If you look at Figure 3 on the project page (the power supply schematic) you'll see that there are two different types of ground symbols used. Those that look like a parallelogram are chassis grounds. These are tied to all the chassis metal in the enclosure. Those that look like triangles are signal grounds. These are tied together but are independent of the chassis grounds. Then the two different types of grounds are tied together via the ground lift switch. The text in the project article explains why this is a good idea.
Below is a copy of Photograph 3 from the project page (underside) with some labeling added for clarity.
Attachment:
Screen shot 2014-01-28 at 5.12.05 PM.jpg
This diagram shows which types of grounds are where and how the ground switch ties them together. You will notice that (getting back to your original question) that there are two wires running through the center penetration of the divider plate. The black lead is the high voltage rail coming out of the primary filter inductor, the green line is the signal (and power) ground. These connect to points on the terminal strip under the final filter capacitor. So yes, there are two leads coming off the bleeder resistor. The following picture shows how these leads connect to the terminal strip.
Attachment:
terminal strip.jpg
This should make the grounding scheme that I used more clear. Does all of this make sense? Let us know if you have other questions.
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