[AMRadio] 100TH and 250TH advice and or comment

John Coleman jc at pctechref.com
Tue Aug 25 17:04:33 EDT 2009

I think there is at least some truth to this Lee, but I am not sure of why.  By the same token though I have run 250ths for quite some time and with many hours of no use both winter and summer without air conditioning.  They seem to always work the same even though I may only fire them up once or twice a year (much to my dismay).  So I really don't have any good answer for this.  If all the tubes in question were assemble into the 610 at the same time then maybe you could just pass this off as "it was finally time that the air leak got to them".  Don, K4KYV and Tim, WA1HLR have discussed this sort of thing quite a bit as well as deterioration of cathode coatings in both directly heated tubes and indirectly heated tubes.  You may want to consult with them about this.  One thing is for certain, if the final tube is weak then it will be very difficult to get it to produce a wave form output that matches the audio wave form, and it gets worse as the power demand goes up.

-----Original Message-----
From: amradio-bounces at mailman.qth.net [mailto:amradio-bounces at mailman.qth.net] On Behalf Of LEE BAHR
Sent: Tuesday, August 25, 2009 2:20 PM
To: Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] 100TH and 250TH advice and or comment

John Moan (forgot his call and spelling) (SK) in San Antonio used to run a 
few BC-610s.  He always rotated his 100TH and 250TH tubes to keep gassing 
from forming in them.  He had about a dozen BC-610s and around 17 R-390A 
receivers in his shack.   I think he used to say it was bad to lie them on 
their side too.  He seemed to know what he was doing and swore the cycling 
of the tubes was neccessary to keep them alive.  He claimed storing these 
tubes would kill them in time.  I am only talking about 100TH and 250TH 


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