Well I have these schematic of a vaccum tube amplifier, and I'm having some problems to understand some symbols.

What are these symbols in red?

What does exactly CW mean? It should be a logarithmic potentiometer but have that strange down arrow.

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  • \$\begingroup\$ Do not forget to elect the best answer for your questions or nobody will answer them in the future. \$\endgroup\$ – greg Jun 28 '13 at 9:22

RT1 is probably a negative tempco resistor. It has a high resistance value when it's first plugged in, reducing inrush current. But after it heats up it has a low resistance to minimize power loss.

R11 is a potentiometer. The arrow near the "CW" indicates which way the wiper moves when the screw is turned clockwise.

  • \$\begingroup\$ I was looking forward to knowing what the squiggly line on the transformer is :( \$\endgroup\$ – Andy aka Jun 19 '13 at 22:03
  • \$\begingroup\$ What is the function of the C14 ? \$\endgroup\$ – user22230 Jun 19 '13 at 22:22
  • \$\begingroup\$ +1 for RT1. They are called CTN thermistors and they present high resistance when cold. They are used in tube amps to protect heater filaments when they are cold. \$\endgroup\$ – greg Jun 26 '13 at 11:59

I believe the component near the transformer is a thermal switch that would open if the transformer gets too hot. Since it is shown before the black transformer lead, it is probably built into the transformer. C14 probably is used to bypass high frequency noise coming in from the power line.

  • \$\begingroup\$ Well I'm about to buy a equivalent transformer, and I believe that switch wont be there. How could I contour this problem? How can I elaborate a thermal protection circuit for a transformer? \$\endgroup\$ – user22230 Jun 20 '13 at 14:23
  • \$\begingroup\$ @RogérioPaludo, do you have a photo of the transformer? If so, add it to your question; maybe someone will for certain what that symbol refers to. \$\endgroup\$ – The Photon Jun 20 '13 at 15:26
  • \$\begingroup\$ Unfortunately I don't have. I didn't buy it yet! \$\endgroup\$ – user22230 Jun 21 '13 at 14:08

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