[Boatanchors] TX4C problem

[Richard Knoppow]

       My memory is that the 6EJ7 was one of the first "frame grid" 
tubes.  It was magic when announced; very high Gm.  I suspect the frame 
grid construction results in the tubes being very sensitive to tiny 
mis-alignments of the elements.  It may be that the very small changes 
from just time may be enough to ruin them.

On 3/1/2015 11:34 AM, Joe W2KJ wrote:
> I agree with Garey on the 6EJ7 tubes being flakey.
>
> A couple of years ago I bought several NOS Phillips 6EJ7 from a reputable tube dealer on the Internet.
>
> Either they weren't good out of the box or only lasted less than 6 months in my T4XC.
>
> I buy only Sylvania now...RCA, GE are also good...I stay away from anything else.
>
> 			73, Joe W2KJ
>
> On Mar 1, 2015, at 1:11 PM, Garey Barrell wrote:
>
>> Bill -
>>
>> Yes, the 6EJ7 is an 'iffy' tube, even NOS.
>>
>> You should check your dummy load...  those are pretty excessive output powers for a T-4XC, and would translate into almost 500 mA of plate current.  Consider Drake specified a MAX of 350 mA on most bands.  Or, how much reflected power do you measure with the Bird?
>>
>> 73, Garey - K4OAH
>> Glen Allen, VA
>>
>> Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
>> and TR-4/C Service Supplement CDs
>> <www.k4oah.com>
>>
>> Bill Abate wrote:
>>> Bill,
>>>
>>> My T-4XC needed a 6EJ7.  After an alignment I got 150 to 165 watts into a dummy load measured with my Bird wattmeter on all bands. That 6EJ7 made a big difference.  Not sure why yours is so low but the finals seem to be a good candidate.  Also I found a NOS tube did not help the problem when it should have.  When all else fails don't rely on a single tube sub.  Check RF voltage at the 6JB6's grid on each band.
>>>
>>> 73,
>>>
>>> Bill, K3PGB
>>>
>>> Bill and Liz wrote:
>>>> I have been playing with a drake TX4C and, after going through the
>>>> complete alignment process a couple of times, a strange problem
>>>> persists.  I believe the PA tubes to be weak-power output on 10M is
>>>> around 50W in CW mode.  But the radio makes 90W on 160M in spite of
>>>> the fact that there is not enough C in the loading cap and about the
>>>> same on 80M where the loading cap does peak nicely.
>>>>
>>>> However, on 40M there appears to be considerably more drive available
>>>> and power output runs 130W at about 375 ma which I read as being
>>>> normal.  It is less on 20 and 15-around 90W or so output.  I see only
>>>> a bit of power sag key down on 10M.
>>>>
>>>> Can anyone suggest why there is so much more drive on 40M?  Is this
>>>> condition characteristic of the TX4 series?
>>>>
>>>> Bill VE3NH
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL