High Screen Voltage

[Bernie Murphy]

Measure the resistance of the cathode resistor to see if has changed.
Also, by measuring the voltage drop accross the cathode resistor you can
determine if the tube is drawing the appropriate plate and screen current.

Also check the bypass caps for potential degredation of circuit operation.

Have you checked the tubes?  Emission may have fallen as well ....


73, de Bernie, VE3FWF, Ottawa, Canada



----- Original Message -----
From: "Carl C. Miller Jr" <bugmarx at EV1.NET>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Sunday, September 15, 2002 12:38 PM
Subject: High Screen Voltage


> Hello All,
>
> I have a problem similiar to the gentleman which posted concerning his
IG-72
> audio generator. I am working on a non-Heath receiver and the screen
> voltages on the RF amp, and both the first and second IF amps are about
> 50-60 volts above normal. The plate voltage is a little high but not
> extremely so. I checked the screen dropping resistors and they are within
> specs, but there is not much of a voltage drop across them. So, obviously
> there is not much current being drawn. What effect would this have on the
> sensitivity of the receiver, performance etc.? The receiver seems to work
> okay, but not quite as sensitive as it should be. Could it be that contact
> is not good at the tube socket or could there be some other problem? As
> always, any help appreciated.
>
> Carl KA5KAB
>
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