Good morning,
Here are details of repairs I found necessary when one 3-500Z
had a grid-filament short in my TL922:
Destroyed components:
L7 470uH grid RF choke
R22 4.7K grid resistor
D1 diode 1N4007 type, 110v relay/bias power supply
C3 33uH 160v electrolytic (replaced, but may have been OK)
The good grid RF choke measured 3.0 ohms (with 4.7k across it).
The 7.5v 10w zener D2 tested OK.
With assistance from Charley W1TE I am planning to install
new RF chokes with higher current capacity.
I have one question:
Will modern type metal film 4.7K 1/2 watt resistors be suitable
for the grid resistors R22 and R23? Or should we still try
to use the old style composition resistors?
What is the best component to protect the filament/bias transformer
is the event of an unexpected grid/filament short in the TL922?
Regards,
Martin ZL1ANJ
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