[Boatanchors] 6146 question

[Jeff Blaine]

I would not say that the 'B can be swapped for the 'A in all cases.

I had a HT-32A that I recently overhauled.  It was a perfect performer 
in all respects, and I had put in some 'B tubes for the finals because 
the Pd is a bit higher so that should make it more rugged.  But I also 
had done a SS rectifier replacing the original tube (this is driven by 
an inherent weakness in the transformer which tends to short the HV and 
the tube fil windings resulting in quite a mess - a mess contained by 
going with a SS rectifier and removing the use of the rect fils 
windings).  What I noticed was that the rig would break into oscillation 
for 5-30 seconds until the finals were warmed up enough and then it 
stopped.  I hunted for days as to a source cause of that issue in the 
output and everything was just perfect.  Swapped a different set of 'B 
in - same issue.  Eventually I swapped in a set of 'A tubes - and the 
issue was gone.

Now it's very likly that that this transmitter (given the unique set of 
differences vs. OEM configuration) is a unicorn case.  But the point 
here is that the 'A tube and the 'B tube, while being generally 
interchangeable, should not be considered as **universally** 
interchangeable.  And given the relative ease of getting 'A tubes vs. 
the more scarce 'B these days, I would just run the 'A  or no-rev tube 
in the TX - if that's what I had - and not worry about it at all.

Good luck OM!

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 1/28/2024 7:46 PM, manualman at juno.com wrote:
> Registered the tube with who?
>
> My information was taken directly from the documented/issued printed
> specifications.
>
> Pete, wa2cwa
>
> On Sun, 28 Jan 2024 17:01:28 -0800 Richard Knoppow
> <1oldlens1 at ix.netcom.com> writes:
>>      Maybe the case. I don't think RCA registered the tube, I am
>> pretty
>> sure that was Sylvania. Tube designed for mobile use with improved
>> resistance to vibration. If RCA data shows the size to be the same
>> it
>> should be the same.
>>
>> On 1/28/2024 4:19 PM, manualman at juno.com wrote:
>>> There's NO difference in height/length with the 6146's that I can
>> find.
>>> All tubes in the 6146 family are considered T12 bulbs.
>>>
>>> Note: length equates to height.
>>>
>>> RCA 6146A
>>> 3 1/8 inches +/- 1/8 length
>>>
>>> GE 6146A
>>> 3.00 inches minimum length
>>> 3.25 inches maximum length
>>>
>>> RCA 6146B/8298A
>>> 3 1/8 inches +/- 1/8 length
>>>
>>> RCA 6146W/7212
>>> 3 1/8 inches +/- 1/8 length
>>>
>>> NOTE: These length dimensions don't consider the length of the
>> pins but
>>> since the pins go into a socket, who cares.
>>> NOTE: All the above tubes have the same diameter 1 21/32 inches
>>>
>>> In all of these tubes, there are some minor inter electrode
>> capacitance
>>> differences between some models but I never found it to be a
>> problem in
>>> rigs from HF to 50 MHz. The consideration with any of these tubes
>> is
>>> PLATE DISSIPATION and whether the power supply in the equipment
>> can
>>> handle a sub to the 6146B's. The 6146B/8298A (and the Japanese
>> S2001A)
>>> are rated for 35 watts plate dissipation whereas the earlier 6146
>> family
>>> and the 6146W are rated for approximately 25 to 27 watts plate
>>> dissipation.
>>>
>>> Over the years I used 6146B's in my Heathkit Apache, HW-101,
>> SB-101,
>>> SB-102, Valiant, Ranger, Hallicrafters HT-32's, B&W 5100B, and
>> several
>>> Kenwood rigs and all worked very well with these tubes.
>>>
>>> Obviously, at higher operating frequencies with this family of
>> tubes,
>>> inter electrode capacitance, wire dressing, wire positioning and
>> over all
>>> design can play an important part in problem less operation of your
>> RF
>>> amplifier.
>>>
>>> Pete, wa2cwa
>>>
>>>
>>> On Sun, 28 Jan 2024 13:09:27 -0800 Richard Knoppow
>>> <1oldlens1 at ix.netcom.com> writes:
>>>>       Not if the 6146B is too tall. The B really is a similar but
>>>> different tube. This may be of no significance for the Ranger.
>>>>
>>>> Richard Knoppow
>>>> Los Angeles
>>>> WB6KBL
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