The 811A should "show a barely perceptible red color at maximum dissipation" (per the RCA tube manual).
The 30L-1 pushes the tubes a little beyond their limits. Add a little speech processing and they get pushed even harder. 73 Gary K4FMX > -----Original Message----- > From: david knepper [mailto:[EMAIL PROTECTED] > Sent: Monday, December 11, 2006 2:09 PM > To: [EMAIL PROTECTED]; Discussion of AM Radio in the Amateur Service > Subject: Re: [AMRadio] Screen Modulated 813 > > Did you ever know that the 811A's in the Collins 30L-1 do show color under > modulation? If any one of the four tubes does not, then, that tube should > be replaced. > > An 813 normally does not show color, unless the plate is the metal variety > and not the carbon plate. I would agree that this tube should operate > without any blushing whatsoever. > > > Dave, W3ST > Publisher of the Collins Journal > Secretary to the Collins Radio Association > www.collinsra.com - the CRA Website > Now with PayPal > CRA Nets: 3.805 Mhz every Monday at 8 PM EST > and 14.253 Mhz every Saturday at 12 Noon EST > Collins Chatroom - Daily at 4 PM EST on 14.285 Mhz > ----- Original Message ----- > From: "Gary Schafer" <[EMAIL PROTECTED]> > To: "'Discussion of AM Radio in the Amateur Service'" > <amradio@mailman.qth.net> > Sent: Monday, December 11, 2006 1:34 PM > Subject: RE: [AMRadio] Screen Modulated 813 > > > > The 813 and 572 are tubes that should never show color. > > > > 73 > > Gary K4FMX > > > >> -----Original Message----- > >> From: [EMAIL PROTECTED] [mailto:amradio- > >> [EMAIL PROTECTED] On Behalf Of Jim Wilhite > >> Sent: Monday, December 11, 2006 12:24 PM > >> To: Discussion of AM Radio in the Amateur Service > >> Subject: Re: [AMRadio] Screen Modulated 813 > >> > >> You are most correct John, I was speaking of power tubes not > >> the lesser cousins. I didn't make that clear but in light > >> of the subject, I plead not guilty. > >> > >> Jim > >> W5JO > >> ----- Original Message ----- > >> From: "John Lawson" <[EMAIL PROTECTED]> > >> To: "Discussion of AM Radio in the Amateur Service" > >> <amradio@mailman.qth.net> > >> Sent: Monday, December 11, 2006 10:35 AM > >> Subject: Re: [AMRadio] Screen Modulated 813 > >> > >> > >> > > >> > > >> > On Mon, 11 Dec 2006, Jim Wilhite wrote: > >> > > >> >> Yes, but we in the amateur service do not even consider > >> >> running them at the max. Red is ok if you take into > >> >> consideration all parameters and follow design > >> >> considerations. > >> > > >> > Dave Knepper also writes: > >> > > >> >>The reason that the tube is a bit cherry red is to > >> >>continually remove built-up gasses inside the tube. > >> > > >> > > >> > > >> > There is a wealth of practical, hands-on - and also > >> > theoretical, knowledge available on this List - a rarity > >> > among reflectors to be sure. Jim has provided myself and > >> > many others with constant 'good information' regarding AM > >> > transmitting gear. > >> > > >> > > >> > But.... but but but: Speaking as a design engineer, > >> > lifelong tube-geek, and (moderately succesful) thermionic > >> > designer - I would like to make the point that plate > >> > incandescance may, or may not, be 'OK'.... depends on the > >> > device amd the regime it's run in. > >> > > >> > > >> > Unless designed for such dissipation, it is most > >> > certainly NOT OK to run many tubes at a blush. The > >> > venerable 6146 is a case in point - running the plates red > >> > in a 6146 alters them irreversibly and generally kills > >> > 'em... get a 'fresh' one, test it for Gm, run it good and > >> > red for a while, then re-test. ooops.... > >> > > >> > There are of course tubes designed to run red, even > >> > bright yellow - like the various radiation-cooled tubes - > >> > IIRC 4-65s, etc... There are some tubes, like the 833, > >> > that can stand a little color and not get terribly upset. > >> > > >> > > >> > Running plates red does not, in most cases, re-adsorb > >> > gasses - if anything it facilitates thier release - > >> > depends entirely on the plate alloy, thickness, and any > >> > coating, element spacing, grid material and design, spacer > >> > materials, etc., etc.. You can't just make generic > >> > generalizations like this... the situation is way more > >> > complex. Red plates also has implications for permanent > >> > grid damage - not to mention that fact that we want that > >> > plate to collect electrons, not emit a bunch of them... ;} > >> > > >> > > >> > And as for "running them to the max" - all tubes have a > >> > point of maximum 'efficiency' where the power transfer > >> > function is optimal. Is the plate red at that place under > >> > the curves? If it's a radiation-cooled tube, you bet. If > >> > it's a 6146 - it just died. And just who is the "we" you > >> > speak of? ;} I run my Valiant on the raggedy edge most of > >> > the time - and I've chewed up one brand new set of finals > >> > finding out just where that edge is... d'oh! But now I > >> > know just how to get the max out of the transmitter and > >> > still keep the Output Devices happy - even if I do make > >> > 'em sweat good and hard... > >> > > >> > > >> > Anyway - the study of the theory and design of vacuum > >> > tubes is pretty damn fascinating to me - and if anyone is > >> > interested, I have a fairly comprehensive bibliography on > >> > the subject that I'd be happy to post, if there is any > >> > interest. And seeing as how most of us are using power > >> > tubes, and building / operating devices using power > >> > tubes - might save some bucks in the long run. > >> > > >> > > >> > Just my 200 millidollar for a Monday Morning... > >> > > >> > > >> > > >> > Cheers and Best of the Season > >> > > >> > > >> > John > >> > KB6SCO > >> > DM09fg > >> > > >> > ______________________________________________________________ > >> > AMRadio mailing list > >> > List Home: http://mailman.qth.net/mailman/listinfo/amradio > >> > Partner Website: http://www.amfone.net > >> > Help: http://mailman.qth.net/mmfaq.html > >> > Post: mailto:AMRadio@mailman.qth.net > >> > > >> > > >> > >> > >> ______________________________________________________________ > >> AMRadio mailing list > >> List Home: http://mailman.qth.net/mailman/listinfo/amradio > >> Partner Website: http://www.amfone.net > >> Help: http://mailman.qth.net/mmfaq.html > >> Post: mailto:AMRadio@mailman.qth.net > > > > > > ______________________________________________________________ > > AMRadio mailing list > > List Home: http://mailman.qth.net/mailman/listinfo/amradio > > Partner Website: http://www.amfone.net > > Help: http://mailman.qth.net/mmfaq.html > > Post: mailto:AMRadio@mailman.qth.net > > ______________________________________________________________ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net
