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Re: [Amps] Warm up and on time question...

To: "BJ VOUTE" <fxb1982@hotmail.com>, <dave@nk7z.net>, <amps@contesting.com>
Subject: Re: [Amps] Warm up and on time question...
From: "Carl" <km1h@jeremy.mv.com>
Date: Thu, 15 Dec 2011 08:42:45 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
It would likely be discussed in Care and Feeding or various Application Notes. 
All are available on the Internet. Bill Orr also wrote many articles for CQ and 
QST discussing cooling and other subjects.

It helps to accumulate a good reference library.

Carl
KM1H


  ----- Original Message ----- 
  From: BJ VOUTE 
  To: km1h@jeremy.mv.com ; dave@nk7z.net ; amps@contesting.com 
  Sent: Wednesday, December 14, 2011 8:49 PM
  Subject: RE: [Amps] Warm up and on time question...


  Is there an official Eimac or other tube manufacturer data sheet that 
specifies warm-up/cool-down for a 3-500?  I looked at an Eimac 3-500 sheet and 
must have missed it?
   

  > From: km1h@jeremy.mv.com
  > To: fxb1982@hotmail.com; dave@nk7z.net; amps@contesting.com
  > Subject: Re: [Amps] Warm up and on time question...
  > Date: Wed, 14 Dec 2011 14:00:08 -0500
  > 
  > 
  > ----- Original Message ----- 
  > From: "BJ VOUTE" <fxb1982@hotmail.com>
  > To: <dave@nk7z.net>; <amps@contesting.com>
  > Sent: Wednesday, December 14, 2011 12:38 AM
  > Subject: Re: [Amps] Warm up and on time question...
  > 
  > 
  > >
  > > This is what I gather:
  > >
  > > The AL-82 manual specifies warm up time as "approximately 30 seconds" 
  > > while the AL-80B manual states "10 seconds". I am guessing that the 
  > > chimney type cooling VS the muffin fan cooling method accounts for the 
  > > different warm up times?
  > 
  > 
  > Nope, different manual writers; 30 seconds is better.
  > 
  > 
  > >
  > > W8JI states that to obtain maximum life from an 8877 tube, not to cycle 
  > > the heater (filament) excessively. http://www.w8ji.com/8877_failures.htm 
  > > It stands to reason that this would apply to a 3-500 tube as well.
  > 
  > 
  > Thats nothing new and just common sense copied from as far back as the 
first 
  > AC operated table radio.The military found that out also as the MTBF went 
  > way up when electronic equipment was left on 24/7.
  > 
  > 
  > >
  > > The QRO HF-2000 manual states: "After prolonged operation, let the 
  > > Amplifier run for several minutes without drive applied so the fan will 
  > > cool the tubes before you turn the Amplifier off."
  > >
  > > When I plan on operating an amplifier for 5 hours I leave it on for 5 
  > > hours. I don't think turning an amplifier off and then back on after 30 
  > > minutes constitutes excessive cycling(subjective?), but I consider a tube 
  > > filament to be like a light bulb and it is said that the life of a light 
  > > bulb is shortened by cycling.
  > >
  > > I as well warm up my tube amplifiers for about 5 minutes and let them 
cool 
  > > down to what physically feels like idling temperature to me before 
  > > shutting down. Whether this is necessary or to what extent the tube needs 
  > > to cool down may likely be a topic of debate but common sense tells me it 
  > > does not hurt anything.
  > 
  > Anything over 30 seconds is wasting time on direct heated tubes such as the 
  > 3-500, 572B. 811, etc.
  > 
  > For indirect heated tubes (3CX800, 8874, 8877, etc)follow the tube 
  > manufacturers specs as amp timer circuits tend to vary in accuracy and with 
  > age. Anything more than spec is another time waster.
  > 
  > Carl
  > KM1H
  > 
  > 
  > 
  > >
  > > I'm looking forward to more info about this topic.
  > >
  > > 73, BJ
  > > k0cwo
  > >
  > >
  > >
  > >
  > >
  > >> From: dave@nk7z.net
  > >> To: amps@contesting.com
  > >> Date: Tue, 13 Dec 2011 07:30:30 -0800
  > >> Subject: [Amps] Warm up and on time question...
  > >>
  > >> Hello,
  > >>
  > >> I have an AL-82, my habit is to turn it on, allow it to warm for about 5
  > >> minutes prior to use, use the amp, then turn it back off. Sometimes I
  > >> find that I will be using the amp again within 10 or 15 minutes, maybe
  > >> 30 minutes. Is it better to leave it on for the half hour, or turn it
  > >> off then re power it 30 minutes later.
  > >>
  > >> Does this cause any issues over the long term? Should I just leave it
  > >> on for the half hour? Worried about repeated heating and cooling of the
  > >> tubes.
  > >>
  > >> Dave
  > >> NK7Z
  > >>
  > >> _______________________________________________
  > >> Amps mailing list
  > >> Amps@contesting.com
  > >> http://lists.contesting.com/mailman/listinfo/amps
  > >
  > > _______________________________________________
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  > > Amps@contesting.com
  > > http://lists.contesting.com/mailman/listinfo/amps
  > >
  > >
  > > -----
  > > No virus found in this message.
  > > Checked by AVG - www.avg.com
  > > Version: 10.0.1415 / Virus Database: 2102/4080 - Release Date: 12/14/11
  > > 
  > 


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