On 8/16/2024 10:25 AM, Mark - N5OT wrote:
I am pretty sure of the answer to this question but I'd hate to find
out I am wrong the hard way.
I am running a pair of pretty flat 3CX800s - Alpha 86.
Spec on the tube says maximum grid current is 60ma.
So if my Alpha grid current meter says 70ma, that means it's actually
35ma through each tube, so I'm good? Am I actually in the okay zone
if I see 120ma on the grid current meter?
NO. All the grid meter is indicating is your TOTAL grid current, through
both tubes, is only 70 mA. ESPECIALLY with older, dud-like tubes, you
have no idea whether one or the other is drawing more or less current
than the other; it could easily be the one producing most (or all) of
your remaining power is also drawing all that grid current.
So unless you remove one or the other then measure each separately, I
would not make any assumption about which, or whether both, are still
drawing the same amount of grid current. If just one is still working
pretty well and drawing the majority of current, you could easily blow
it out by assuming that both tubes are still sharing all the current.
Steve K0XP
Thanks in advance.
73 - Mark N5OT
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