[Test-Equipment] HP 3400A nuvistor part number?

[Marco IK1ODO -2]

At 18.19 05/11/2007, you wrote:
>There are the 7586 and 7587. One is a direct swap with a 6CW4 (just 
>selected tolerance) and the other is a multi grid if I remember but 
>forget which is which.
>
>Carl
>KM1H

7586 is a triode, and is a close match to the 6CW4. Not exactely the 
same, have different intertelectrode capacitances, but both will work 
in the 3400A.
However, only one time I found a defective nuvistor in a 3400A; the 
fault may be in several different circuits (bad thermocouple, power 
supply, detection amplifier...) The 3400A is definitively not a 
trivial instrument to correctly debug and calibrate. Also, there are 
several schematics across the 30 years of production... I have at 
least three different paper manuals (one for the '60, one for the 
'70, one for the eighties) and five different versions in PDF.

73 - Marco IK1ODO / AI4YF