Re: AVO CT 160 GAS test
GJ is spot-on. Rather you phooked a home brew test rig than a mega bucks CT160.
AVO VCM's & CT160's indicate a possible gas problem by measuring minute Grid current, ie. uA Ig. For the safety relay to Buzz - indicates excessive Anode or Screen current. Also, if the Anode seems to glow a bright blue, that means its jolly hot & drawing excessive Ia.
Me - I always advise AVO VCM & CT160 owners to set -ve Vg a bit higher than the book value, thus holding Ia back a bit, & it avoids the meter's needle "whanging" to fsd - - CT160's, and the old 2 Panel Testers have always been prone to this. With CT160's, the coarse & fine Ia controls DO NOT actually control Ia, they just balance the voltage bridge network prior to the mA/V test procedure. Sadly, CT160's, (unlike the MK's 1 to 4 VCM's) do not show Ia on the meter. Only the Vg pot controls Ia(the telephone dial-like mA/V pot also controls a very small amount of Vg & hence a very small amount of Ia).
All very complicated, I know, and also it being done with 50Hz ac pulses makes it even more complicated.
Regards, David
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