[R-390] V509 runs hot

[k2cby]

The only thing that will make a triode run hot is excessive grid voltage.

There are three suspects:

            The most likely is a short or leak in the capacitor leading to
the grid from the plate of the prior stage causing the plate voltage to
drive the grid of the following stage positive.

            The less likely (but possible) is a short in the capacitor that
bypasses the cathode resistor, causing the tube to become zero-biased.

            The least likely is a plate resistor or a cathode resistor that
has vastly decreased in value (although the plate resistor may well have
changed value due to excessive current). 

 

Miles B. Anderson, K2CBY
16 Round Pond Lane
Sag Harbor, NY 11963
Tel.: (631) 725-4400

Fax.: (631) 725-2223
e-mail: k2cby at optonline.net