ledvedder
Well-known member
FourT6and2":29fmjymy said:ledvedder":29fmjymy said:FourT6and2":29fmjymy said:ledvedder":29fmjymy said:Ok, here's the existing wires connected to the send and return jacks, and the other end of the wires connecting to the B+ and middle treble wiper. Am I just disconnecting the black wires from the send and return jacks and connecting the to the in and out on the metro board? Where do I get B+ for the metro board?
Just disconnect the coax from the send/return jacks. And attach them to the Metro board. Don't mess with the other ends (treble pot, preamp board, etc.). You can grab the B+ from anywhere, really. As long as you make sure you are using the correct voltage for the Metro board. I think the PI node might be a good place to try. Or the PI-side of the large blue filter cap on the preamp board since it's physically closer (this is the spot connected to V2, pin 6). But it's the same point in the circuit as the PI node since there is no dropping resistor between them.
What do the Metro Board instructions say about the required voltage?
Based on my B+ measurement, I have to use a 33K resistor between the voltage source and the B+ terminal on the metro board.
How do you know this? What is your voltage source? The value of your dropping resistor will vary depending on what B+ source you use. B+ is not constant. It's different depending on where in the circuit you tap it. Voltage in my stock Chupa 50 at the PI B+ node is around 330v, for example. If you're asking where to grab the B+ how do you know what the B+ voltage is and therefore what dropping resistor value to use?
It measured 353. Based on that, the Metro instructions says to use a 33K resistor.