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Bias Probe Schematic On Line

12/9/1997 9:10 PM
Bias Probe Schematic On Line
I have placed the schematic for a super simple four tube bias probe on line on my web page at  
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This is pretty basic, just a four way switch to switch a Digital Panel Meter between four 1 Ohm 1% resistors in the cathode connection of four remoted tube sockets.  
I prefer dedicated tools, but if you want to save $10, you can put in contacts to clip your multimeter set to 200mVDC to the switch commons, of course.  
You can also build it for only two tubes, natch.  
The hard thing to find is the octal plugs. I'm told they're in the Newark catalog; I have scavenged them from dead tubes by unsoldering the pins after breaking away the tube before. Octal relays are another way to do this.  

If you do this, be sure to use at least 600V rated wires on the plate and screen leads, preferably all of them.

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