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Robin, Here is a problem that may be similar to yours: https://www.eham.net/forum/view?id=topic,112624.0.html I had the shorted Q2 problem as well in my Centurion. 73 Bill N4LG PS: Another problem is

Especially the carbon comp ones under about 1K, above that, they tend to go high when overloaded. Sent: Monday, July 15, 2024 10:28 PM To: [email protected] Subject: Re: [ham-amplifiers]

Depends on the resistor. Some go very low in value Sent: Monday, July 15, 2024 10:13 PM To: 'Chuck Neal'; [email protected] Subject: Re: [ham-amplifiers] Ten-Tec Centurion, new tubes, idle

Seems to me that a burnt shunt would make the meter read high. 73 – Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 908-902-3831 Sent: Monday, July 15, 2024 9:06 PM To:

Lou, If you're talking about my photo, i cannot read any brand on it. The photo is from an original AL-80 (no A or B). That tube was in this amp when I bought it in 1994. An ole Timex watch! Bob W4JFA

It takes 5 seconds to test the zener to see if it’s good. Sent from the all new AOL app for iOS

If the zener is shorted the idle current goes way higher thsn 125ma. ?So I doubt it’s shorted. Sent from the all new AOL app for iOS

That negative bias is sometimes done with a zener in series with the CT od the filament transformer. When that goes, no negative bias. I’ve seen that many times, since zeners are not very good in

Sounds like two problems at once 1) Plate meter is reading low, perhaps due to a burnt shunt resistor in the metering circuit AND 2) Bias supply is not working depending on the plate voltage in that

If your plate meter reads 125 ma at idle the tubes are immediately dissipating 375 watts with no drive. ?Immediately turning red on the bottom bell at 375watts is a bit quick. ?Are both tubes

I think Lou meant after a period of being keyed, rather than the age of the tubes. 73, Alek VK6APK

"Over time the bottom Bella of the tube will definitely turn red even with no drive." The brand new tubes did this right out of the box...no time elapsed. [email protected]> wrote:

Thank you; I did not see this ammeter in the instructions manual. It seems difficult to manufacture power electronic tubes with a solid grid structure. Chinese manufactures often have a fragile grid.

Oh Sorry, normal idle current is 125–160ma. Over time the bottom Bella of the tube will definitely turn red even with no drive. Sent from the all new AOL app for iOS

Thanks for the info, Louis. To be clear, the photo you're referencing is from Bob W4JFA, not from me or my amplifier. My tubes from Tom Rausch of CTR Engineering do have white bases.

Thanks Bob. My tubes glow similarly in the lower plate portion when keyed without drive, but only a dull red. The photo you sent makes the plate look white hot...maybe it is an overexposed photo.

Francois, In addition to the meter described in your quote from the manual, there is another meter dedicated to Iplate. It's a 0-1A meter. [email protected]> wrote:

How do you measure plate current? Manual <http://www.tentec.com/wp-content/uploads/2016/05/model_422_centurion_owner_manual.pdf> -- F1AMM Fran?ois De la part de Bob Envoyé : lundi 15 juillet 2024

The tube in that photo, does that tube have a white base to it? ?It looks like there is no white base and the white looks to be a reflection of the filament light. ?If this is so, that tube didn’t

I hope the attached picture shows. This is a 3-500z with approx 90 - 100mA plate current after about 60 - 90 seconds. Bob W4JFA [email protected]> wrote: