[Boatanchors] TX4C problem

[Garey Barrell]

Bill -

OK.  You sure that's not a TR-4!!  :-)   I've never seen one over 55%.  That's six (6) times the 
'rated' (CCS) dissipation in those poor little 6JB6s.  Did you check for plate 'color'? I 
wouldn't hold the key down for long.....  :-)

I wonder what the distortion products look like?  Considering Drake suggested limiting to 340 mA 
on 160, 80, 40 & 20 to meet the OLD FCC 'Purity of Emissions' specs.  I hope you have a fan on 
it!  :-)

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:
> Garey,
>
> The dummy load is fine.  There is negligible reflected power.  The power input is about 270 
> watts.  So its about 60% efficiency if the Bird is right.  I have no reason to doubt it as it 
> tracks with other wattmeters and what I would expect from my other rigs.  The efficiency does 
> appear high.  I'm not too concerned as I use the numbers as a benchmark only to gauge when 
> things are going south. My meters are not NBS traceable! :)
>
> 73,
>
> Bill, K3PGB
>
> 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