Mark-
My LC800 was arcing and tripping out.
Turned out to be the plate tuning cap.
Once they start arcing it’s tough to fix ‘em. Tried filing and cleaning up the
carbon tracks, but eventually ended up replacing it with a vac variable.
That amp uses 3 3cx800’s.
I figured it was abused by the previous owner.
I realize this doesn’t exactly answer your question, but might save you some
grief in case you have the same thing going on.
Tom
K0SN
> On Aug 19, 2024, at 4:52 AM, Mark - N5OT <r-emails@n5ot.com> wrote:
>
> Thanks everyone for all the comments.
>
> I figured the idea of whether the two tubes were the same or different would
> enter into the conversation. I am guessing that the meter on an amp with 2
> tubes in this case will show the total grid current regardless of whether one
> tube is drawing more than the other. The seat of my pants says that if the
> two tubes started out new and matched (an assumption, I know) and have the
> same amount of "experience" in this single application, they they are likely
> still relatively balanced. I realize I could be wrong.
>
> Anyway, I have been using it to transmit 1500 watts over the weekend and with
> it tuned like JC N4IS describes (I already knew all that but I'm glad to have
> my opinion backed by a competent authority) the grid meter LEDs are never
> above 70ma.
>
> When an amp trips out, how does one know if it is the tube that flashed over,
> or something else? I use a number of matching networks and there is the
> occasional arc which shoots the SWR high and the amp trips out. If it was a
> tube, how would I know?
>
> 73 - Mark N5OT
>
>
>> On 8/16/2024 12:25 PM, 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?
>> Thanks in advance.
>> 73 - Mark N5OT
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