Re: [Drakelist] T-4XB neutralization?

[Ron Baker]

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]>
[EMAIL PROTECTED]>
To: "WA3WOM" < <[EMAIL PROTECTED]>
[EMAIL PROTECTED]>; < <mailto:drakelist@zerobeat.net>
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
> < <http://www.k4oah.com> 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
>> 

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