Finally joined the club! (CTC-9 content)

[leadlike]

Would you mind explaining how to hook all of this up to monitor cathode current? I've just about got my '9 dialed in, but I'm afraid to run it for long periods as I have little understanding of how to do this. The Sams says to remove a jumper, but I have yet to see where this jumper is at that I can hook my ammeter to...

[miniman82]

Originally Posted by leadlike

Would you mind explaining how to hook all of this up to monitor cathode current?

Sure, but let me explain my way of doing it as well.


Sams has you use different moving needle meters to make the measurements: a 0-1ma meter for the 6BK4 cathode, and a 0-500ma one for the 6DQ5. Normally you would either unsolder a ground connection (in the case of the 6DQ5), or clip a little wire jumper (on the 6BK4) and place the meter inline to take current readings. Instead, I chose to permanently install 1-ohm 5-watt resistors from the cathodes to ground. This allows me to set the DMM to read voltage instead, so I can move 1 meter around vice watching 2. It gives the same exact readout as it would if you were reading current, I just think it's easier to move leads around to different resistors.

Plus it's somewhat less dangerous-not so many wires to run into while making adjustments. And even if I did bump a lead loose, there's little risk of hurting anything since the circuit would still be complete. If you measure current with an inline meter on the 6BK4, I shudder to think what would happen since the high voltage would be instantly unregulated if a current meter lead came loose.

The Sams says to remove a jumper, but I have yet to see where this jumper is at that I can hook my ammeter to...

For the 6DQ5, you have to remove the ground wire on pin 3/6 for a current reading/install resistor for voltage reading. On the 6BK4, you have to follow a wire from pin 1 back to a terminal strip. On the strip, you'll find a little loop of wire. Clip that loop, and insert the current meter or install the resistor.