WA3WOM
Fri, 29 Aug 2008 16:49:39 -0700
Thanks Ron. I have received several REALLY good suggestions from "you * the other experienced Drake guys" so I will experiment and let you all know what I find. Thanks a ton... WA3Worn-Out-Mike ----- Original Message ----- From: Ron Baker To: drakelist@zerobeat.net Sent: Friday, August 29, 2008 3:29 PM Subject: Re: [Drakelist] T-4XB neutralization? For what it's worth, I have found the Sylvania by far are the best but I have found no matter whether its a Sylvania, RCA, or GE, they all will neutralize in the transmitter as the circuit was designed by Drake. I have found when a tube would not properly neutralize the tube was either bad or weak or on the verge of going bad. Also if your looking for a dip on 10 meters first put the loading to "0", or to the far left. This will give you the maximum "dip" effect. Advancing the loading from that point the "dip" becomes more shallow and less apparent on the meter. Regarding the final tubes stay with the above mentioned brand tubes. I have found most of the other brands have a tendency to not do well especially on the higher bands. I found the "International" brand tubes to be the absolute worst possible final tube to use in Drake. I acquired several brand new International and ended up tossing all of them because everyone appeared somewhat different, and forget trying to find a match pair. 73, Ron / WB4HFN ------------------------------------------------------------------------------ From: [EMAIL PROTECTED] [EMAIL PROTECTED] On Behalf Of WA3WOM Sent: Friday, August 29, 2008 1:39 PM To: [EMAIL PROTECTED]; drakelist@zerobeat.net Subject: Re: [Drakelist] T-4XB neutralization? I have 10 more matched sets of NOS 6JB6s to try. So far, I've tried one pair from Sylvania, 1 pair of RCAs and 1 pair of GEs and could not neutralize any properly. No obvious dip "by the book". I have lots more to try, I just got frustrated after the third apparent failure... I will have to take a look at the manufacturer codes and see who made what. I was just hoping to get off easy with a little cap here or there. ;-) I will also get out the magnifying glass and check everything visually and also check voltage readings although it loads and seems to work perfectly on the air. Gary gave me an idea to try - disconnect the HV to the plates and adjust for minimum RF at the antenna jack. I will give that a shot next week while I'm off. Thanks, WA3Worn-Out-Mike ----- Original Message ----- From: "Garey Barrell" <[EMAIL PROTECTED]> To: "WA3WOM" <[EMAIL PROTECTED]>; <drakelist@zerobeat.net> Sent: Thursday, August 28, 2008 11:09 PM Subject: Re: [Drakelist] T-4XB neutralization? > Mike - > > Before you expend too much effort in this, do you have ANY tubes that > will neutralize? The RCA and Sylvania tubes were very close to the > same and either should neutralize without difficulty or changes. I HAVE > used GE tubes without difficulty also, aside the from fact that they > seemed to fall off in output power more quickly from brand new than > either Sylvania or RCA brands. I wonder if by the time that Service > Bulletin was issued if the "GE" branded tubes may in fact not have been > manufactured by GE. > > Back in the 60's, Sylvania 6JB6s (and all Zenith branded tubes) were > manufactured by Sylvania. RCA 6JB6s were manufactured by RCA. By the > mid 70's, tubes were being "cross-manufactured" and branded as tube > manufacturing plants were being shut down. So a GE branded tube may in > fact have been built by another company. > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 4-B, C-Line & TR-4/C Service Supplement CDs > <www.k4oah.com> > > > > WA3WOM wrote: >> A Drake technical bulletin issued when Drake could no longer get >> Sylvania 6JB6s and they had to begin substituting GE brand ones, says >> the following: >> >> /The T-4X series transmitter uses a 6 pf @ 2KV padder capacitor (C-48) >> across the neutralization capacitor (C-49). You must experiment with a >> small value capacitor across the existing padder C-48 to achieve >> proper neutralization./ >> >> I have several sets of matched GE and RCA brand 6JB6s that I am having >> trouble neutralizing. Anyone have any idea what "_small value >> capacitor_" means in this context? >> >> TNX ES 73 DE MIKE WA3WOM K >> ------------------------------------------------------------------------------ _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
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