[Amps] General question on filament life

[Robert B. Bonner]

Gary and I have been discussing this most of the afternoon… Much of what we’ve been talking about is along the lines of what Lou stated here.

Basically within reason, I will turn my amp off if I will not be using it for a couple hours.  I usually will not do more than two cycles a day.  Most of my operating is evening, one cycle.

Like PHIL, my amp comes on when the radio does, but I know I’m going to be transmitting.

I currently don’t have a standby switch, but I don’t need one.  ☺

I mentioned Gary should be able to get a good 15 years worth of use out of his tubes if he follows good operating sense and doesn’t make a mistake with them.

If he ran them continuously I estimate 3 years.  Cycling them reasonably will get you to 15 so why burn the candles?  The owner of my 77DD got 15 years out of the 8877’s before he replaced them.  I consider that just peachy.

I figure it’s a sliding window of use.  Never turn them on, lasts almost forever, hahahaha.   Run them forever and they last 3 years.  Judicious use and you get 15 years. 

I am curious, how many of you guys have put a current meter on your filaments?  I did once and scared the crap out of myself.  When ramping up the filaments before they START TO GLOW, they are VERY low resistance and the current is crazy!!!  I highly recommend getting past that point rather quickly and on to the fine adjustment to set the voltage.

IF you did a filament step start I WOULD NEVER CONSIDER ANYTHING LONGER THAN 1 SECOND because of this high current scenario.

BOB DD

________________________________________
From: Gudguyham at aol.com [mailto:Gudguyham at aol.com] 
Sent: Thursday, February 08, 2007 5:31 PM
To: rbonner at qro.com; garymyers at powerc.net; amps at contesting.com
Subject: Re: [Amps] General question on filament life

In a message dated 2/8/2007 3:25:42 P.M. Eastern Standard Time, rbonner at qro.com writes:
How many bulbs have you had fail the first time you turned it ON?  I have
had a lot.  When you are cycling, you will have results all over the map
whether you step start it or not as each tube is an individual.  Some die at
birth, and some live to be 114 years old.
I have been thinking about this subject a lot myself.  This is what I have concluded.  Since ham radio is an occasional thing we do with little transmit time compared to off time or listening time.  Seems like it would be senseless to leave your filaments running 24/7.  On the other hand if you cycled them a lot that could be costly too, so for hams as Bob says it probably makes little difference.  But I think the ideal situation would be to turn off the filament when not in use and to bring the filament up slowly with a variac to proper operating voltage every time you use the amp.  It would be a pain to do that every time, but all that hassle aside, it might be "the best" thing.  Of course you could argue that one mistake could be costly, but I am speaking only as everything being perfect.  It's just not practical though.
 
For what is it worth, here is what I do.  When I go on the air I do not turn on the amplifier unless I need to use it.  If I know I am going to use it, I will then turn it on, it will stay on until I am done hamming for that session.  I won't shut it off if I know I might be using it again even an hour later like after dinner or something.  I would NOT cycle it on and off as I needed it for a hamming session.  This is why I always put a standby switch on all my SB-220 amps.  Many times I did not use the amp and then suddenly I would and then again I would not.  The standby switch came in handy so I didn't have to cycle the filaments.  You all notice that USUALLY when a light bulb burns out it is when you first turn it on.  Only my 2 cents.  Lou