Quote:
Originally Posted by Dekatron
Did you use ferrite beads on all wiring for the valve sockets?
Have you tested with a grid stopper resistor?
It could be that the valve under test is oscillating which can result in strange behaviour when measured, it can even affect the tube tester so that it doesn't regulate the voltages correctly and even affect the oscillator used to drive the grid.
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I second that, whilst testing the valve and getting strange results, try placing your hand around the glass envelope. If it causes changes then the valve is oscillating. In the past I have used a few turns of Grounded wire wrapped around the envelope and moved this loop up and down to stop the oscillation. This is only a problem I find with valves like EL34 and some KT88's. I may try fitting a grid stopper in just the octal base for these valves and hope that other valves tested in the socket are not affected by the resistor.
Les