27-11-2016, 05:26 PM
(This post was last modified: 27-11-2016, 05:38 PM by Mike Watterson.)
If it was mA/V, then good or bad might depend on the valve.
Isn't there a switch and an adjustment knob for mA/V mode?
mA/V needs a change in input to measure gain.
Replace / Good is usually just actual absolute current, emission. Again though without settings per valve type, it doesn't mean anything.
So in one state it's a very primitive go/fail, but only probably for particular valves as low current is bad on an 6V6 or EL34 or PX4, but fine on an HL1 or EF39?
The other state is ma/V and you need to check the valve data and also change the input to read it.
The needle isn't at zero in the photo.
Tests at say 70% means that the Ia is 70% of what the quoted figure is for that valve at makers setting of Vg1, Vg2 & Va. I think for many types 66% might still count as "OK". The reading can be 120%, i.e. 1.2 times more that quoted in data sheet. Unless you know that the correct Vg1, Vg2, Va and Vh was uses, the % test figure is meanigless and it's only one parameter, though an indication of wear. A valve might still be usable even at 30%.
Isn't there a switch and an adjustment knob for mA/V mode?
mA/V needs a change in input to measure gain.
Replace / Good is usually just actual absolute current, emission. Again though without settings per valve type, it doesn't mean anything.
So in one state it's a very primitive go/fail, but only probably for particular valves as low current is bad on an 6V6 or EL34 or PX4, but fine on an HL1 or EF39?
The other state is ma/V and you need to check the valve data and also change the input to read it.
The needle isn't at zero in the photo.
Tests at say 70% means that the Ia is 70% of what the quoted figure is for that valve at makers setting of Vg1, Vg2 & Va. I think for many types 66% might still count as "OK". The reading can be 120%, i.e. 1.2 times more that quoted in data sheet. Unless you know that the correct Vg1, Vg2, Va and Vh was uses, the % test figure is meanigless and it's only one parameter, though an indication of wear. A valve might still be usable even at 30%.
