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I'd like to query the collective knowledge about a Ten-Tec Centurion amplifier I've been working on, if you'd be so kind as to respond:

I found that one tube had a cathode to grid short. I ordered and received a new pair of 3-500ZG tubes from Tom at CTR Engineering. I installed the tubes and it makes power.

With the amp keyed into a dummy?load & no drive, I see an indicated plate current of ~125mA, which I think is normal for a pair of 3-500Z tubes?in grounded grid; please comment on that. More to the point, the bases of the tube plates glow a dull red in that condition. I've been told by an elmer who I'm inclined to trust that the plates shouldn't glow with only 125mA plate current, and if they are glowing in keyed/idle, then the indicated plate current is likely false & for some reason greater than 125mA.

The original fault that I found is one tube has a short between grid and cathode, the other tube doesn't show any shorts. Is it possible or likely that some of the resistors used to derive?the plate current indication were damaged by the shorted grid/cathode condition?

If the plate current is greater than 125mA, what would cause that? I'm aware that Ten-Tec had some problems with bias from the QSK board in these amps for a time, but I don't know anything more about that. Any info is appreciated.

I recorded these parameters on each band; measurements taken from the front panel meters of the amp. I stopped at 1kW output because I don't have a slug for my Bird 43 that will indicate above 1kW on HF frequencies.?

?

Band	Load	Tune	Pin	Pout	Iplate ma	Igrid ma
160	10	8	80	1kW	600	180
80	10	5	55	1kW	630	140
40	10	2.5	80	1kW	440	160
30 (40)	1.6	0.75	50	1kW	450	160
20	6	0.75	50	1kW	500	170
17 (15)	7.4	1.25	60	1kW	630	160
15	6	0.75	80	1kW	530	160
10	5	0.5	75	1kW	600	160