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Author Topic: Leaving an amp on all day.....  (Read 1215 times)
KB4MNG
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« on: December 06, 2017, 06:26:58 AM »

I know there are some hard core ops that leave their stuff on all day, day after day. Anyone leave a tube amp such as a 3-500 for that long of a time? Just wondering how the tube would hold up. I know an ameritron tech was interviewed. One of their ceramic tubes that is quite expensive was used in this manner for 16 years and held up fine.
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KB6HRT
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« Reply #1 on: December 06, 2017, 07:44:16 AM »

 Older HAM not a big tube guy, had a Ameritron 811a amplifier for about 5+ years around 2000, only used it on 75m in one place on 75m never retuned, just turned it on and off everyday, ran it full tilt everyday, first set of tubes lasted 3 1/2 years, with todays tubes they would not have lasted 2 weeks, was told retuning your amplifier shorten's tube life because tubes go through a slity different heat cycle more often an its the heating an cooling mechanical cycle that takes the toll on the tube, in my case the 811's blower fan made noise an I did not want to hear the noise, today use a ACOM 1500 an noise not a problem, today I leave the ACOM on because I forget to turn it off, not been a problems so far, also have a SCG 500 Cube Amp (no tubes) forget to turn it off lots of times, using it since 2009, again no problem........ YOU know I can't remember S@#$ these days.......hmmm now THAT'S a problem, so far so good with these two amplifiers .....73s...........kb6hrt
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WB2WIK
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« Reply #2 on: December 06, 2017, 09:38:26 AM »

I know there are some hard core ops that leave their stuff on all day, day after day. Anyone leave a tube amp such as a 3-500 for that long of a time? Just wondering how the tube would hold up. I know an ameritron tech was interviewed. One of their ceramic tubes that is quite expensive was used in this manner for 16 years and held up fine.

The metal-ceramic tubes (external anode) may hold up better, but I wouldn't leave a 3-500Z amp on all the time if not in use.   They're "instant-on" tubes, so when needed, turn the amp off.

Filament life isn't infinite, and "some" amps run them outside their specified range (including on the "high side") which will shorten life to begin with.
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K8AXW
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« Reply #3 on: December 06, 2017, 10:36:54 AM »

I've never found any benefit of leaving anything ON if not being used! 

My pair of 3-500Zs and 572Bs get turned on very infrequently anymore and both sets are over 30 years old!

For many years they were on and off, several times a day.

 I don't trust anything.  I never leave the house with the clothes dryer on and always shut off the water supply to the clothes washer when not in use.

When the heat or AC is being used, I am aware of them.  Anal retentive?  Perhaps. It takes only one "Aw shit!" to ruin your life or maybe just a chunk of your bank account.
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KM1H
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« Reply #4 on: December 06, 2017, 03:18:09 PM »

I see no reason to leave an amp on 24/7.

If a 3 minute warm up delay shrivels your shorts either learn to live with it or get an instant on amp or SS.

In over 50 years of having a delayed on amp (starting in 1964 with a NCL-2000) Ive never missed a new country and have learned to wait the 1.5 to 3 minutes or turn it on when I plan to be on for awhile.

Carl
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NA4M
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« Reply #5 on: December 08, 2017, 07:29:23 AM »

Leaving an amp on for long periods is one thing.  Turning it on/off repeatedly over shorter time frames is another.   Unless an amp has in-rush current protection, every time it's powered on it may be subject to large in-rush currents from cold filaments, discharged p.s. caps, etc. that stresses components.    Thats likely the reason many choose to leave an amp on for extended periods. 
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N3QE
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« Reply #6 on: December 08, 2017, 08:03:46 AM »

I know an ameritron tech was interviewed. One of their ceramic tubes that is quite expensive was used in this manner for 16 years and held up fine.

I betcha he was talking about the 3CX1200A7, which is unusual for a ceramic tube in that it has a thoriated tungsten filament.

Most of the ceramic oxide-coated cathode Eimac tubes are usually rated for 10-20,000 hours of heater on time. And don't do a lot more than that according to the folks I've worked with in the MRI industry. The mental model the experts have given me, is that the oxide-coated cathodes get used up even if no plate current is being drawn.

20,000 hours = a little over 2 years if on 24x7.

I wonder if the
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KM1H
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« Reply #7 on: December 08, 2017, 09:00:17 AM »

Quote
Leaving an amp on for long periods is one thing.  Turning it on/off repeatedly over shorter time frames is another.   Unless an amp has in-rush current protection, every time it's powered on it may be subject to large in-rush currents from cold filaments, discharged p.s. caps, etc. that stresses components.    Thats likely the reason many choose to leave an amp on for extended periods.

Commercial ham power level amps are usually designed so that adding a step start is a waste of time and money.
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K1ZJH
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« Reply #8 on: December 08, 2017, 09:06:09 AM »

Tubes like the 4-400 and even the 3-500 were used in military and commercial broadcast transmitters designed to run 24/7/365.  But, they were engineered to do so...  I don't see any valid reason to power an amp when I am not sitting at the operating desk. Waste of power, and of tube and filter capacitor life.

Pete
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G3RZP
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« Reply #9 on: December 11, 2017, 09:30:38 AM »

For a number of thoriated filament types, RCA recommended reducing filament voltage to 80% in standby and turning off if the period would exceed 15 minutes. I think I would like to see a step start arrangement to avoid the surge when the filament is cold.

73

G3RZP
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AC2RY
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Posts: 306




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« Reply #10 on: December 11, 2017, 10:15:22 AM »

For a number of thoriated filament types, RCA recommended reducing filament voltage to 80% in standby and turning off if the period would exceed 15 minutes. I think I would like to see a step start arrangement to avoid the surge when the filament is cold.

73

G3RZP

Thoriated direct heated cathodes have long life, but get gamaged in on-off cycles. Oxide indirectly heated cathodes have limited life span and less sensitive to on-off cycles. Each type of tube has its guaranteed life specified in datasheet. This value assumes 27/7 operation.

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KA5ROW
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« Reply #11 on: December 11, 2017, 11:03:09 AM »

A local radio station used 4-400 tubes transmitting 24/7 they said that the tubes last years. so intermingle use of ham radios should last a life time. They used two for RF out and two for auto out, now they were Eimac tubes but I would think the tubes made in red china should hold up for many years as they are an exact copy.

The radio station put out 500 watts.
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KM1H
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« Reply #12 on: December 11, 2017, 11:53:37 AM »

Quote
For a number of thoriated filament types, RCA recommended reducing filament voltage to 80% in standby and turning off if the period would exceed 15 minutes. I think I would like to see a step start arrangement to avoid the surge when the filament is cold.

As I have already stated above a properly engineered ham amp has all the inrush protection needed in the filament and HV transformers or all combined in one.

Quote
A local radio station used 4-400 tubes transmitting 24/7 they said that the tubes last years. so intermingle use of ham radios should last a life time. They used two for RF out and two for auto out, now they were Eimac tubes but I would think the tubes made in red china should hold up for many years as they are an exact copy.

I have been maintaining a Bauer 707 for decades; two each 4-400A's for RF and audio. At daytime only with that rig the tubes are about 8 years old.
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KB2FCV
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« Reply #13 on: Yesterday at 08:36:27 AM »

I see no reason to leave a tube amp on 24/7/365 unless you are a broadcast station. It's a waste of electricity. My SB-200 gets used maybe a few times a month... maybe a little more so in wintertime when chasing stuff on the low bands.

If needed, I will turn my amp on when I begin operating. The only time I might leave it on unattended is if I briefly head upstairs to eat breakfast/lunch/dinner, use the bathroom, etc. When I'm done operating and know I likely won't need it I'll then shut it off.
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