[Boatanchors] 6146 question

Sun Jan 28 21:19:24 EST 2024

You have to reneutrelise when switching to different tube types.

73
Gary K4FMX 

Gary Schafer

> On Jan 28, 2024, at 8:03 PM, Jeff Blaine <KeepWalking188 at ac0c.com> wrote:
> 
> 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
>> ______________________________________________________________
>> Boatanchors mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Boatanchors at mailman.qth.net
>> 
>> List Administrator: Gary Harmon, K5JWK
>> ** For Assistance: gharmon at idworld.net **
>> 
>> 
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to keepwalking188 at ac0c.com
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
> 
> List Administrator: Gary Harmon, K5JWK
> ** For Assistance: gharmon at idworld.net **
> 
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to garyschafer at largeriver.net