[R-390] Tube Swapping in IF Deck

[Jim Whartenby]

I read the article and agree with the sentiment that existing tubes (aka used) may perform better then new tubes.  Reliability wise, they should be beyond the infant mortality phase of the bathtub curve so that is a plus.  It seems that no two tubes of the same type perform the same in a particular circuit.  Swapping them out to increase overall performance makes sense.  That would be literally "pushing the envelope!"  <grin>  Of course the tube that was replaced may outperform in another circuit so it is a win-win.  

The only bad tube is one with an open heater or one with shorted elements, both of which are rare events, in my experience.  Even tubes with lower emission may perform better in some circuits.

Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy 

    On Tuesday, October 15, 2024 at 11:39:04 AM CDT, Barry <n4buq at knology.net> wrote:   

 Yes - I think I found what I was looking for in that document.

Thanks to all,
Barry - N4BUQ

----- Original Message -----
> From: "R-390 Mailing List" <r-390 at mailman.qth.net>
> To: "Barry Scott" <72volkswagon at gmail.com>
> Cc: "R-390 Mailing List" <r-390 at mailman.qth.net>
> Sent: Tuesday, October 15, 2024 11:05:01 AM
> Subject: Re: [R-390] Tube Swapping in IF Deck

> Bet Roger's post & others will be found in
> https://r-390a.net/Pearls/sensitivity_alignment.pdf
> 
> Craig:WD8KDG
> 
> -----Original Message-----
> From: Barry Scott <72volkswagon at gmail.com>
> Sent: Tuesday, October 15, 2024 8:40 AM
> To: hamfish at comcast.net
> Cc: R-390 Mailing List <r-390 at mailman.qth.net>
> Subject: Re: [R-390] Tube Swapping in IF Deck
> 
> I don't see any posts from that date in the version of the Pearls I'm looking
> in.  Maybe it's in a different version somewhere?
> 
> Thanks,
> Barry - N4BUQ
> 
> On Tue, Oct 15, 2024 at 10:34 AM <hamfish at comcast.net> wrote:
>>
>> Barry & All,
>>
>> I saved that reply from Roger KC6TRU, dated Monday, September 26, 2005
>> @ 6:35PM. Most likely saved in Pearls? Someone might need a warehouse
>> full of vacuum tubes. I'm glad to have a few replacements.
>>
>> Regards,
>> Craig:WD8KDG
>>
>> -----Original Message-----
>> From: r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> On
>> Behalf Of Barry Scott
>> Sent: Tuesday, October 15, 2024 8:12 AM
>> To: R-390 Mailing List <r-390 at mailman.qth.net>
>> Subject: [R-390] Tube Swapping in IF Deck
>>
>> I seem to recall a post many years ago from Roger Ruszkowski regarding
>> swapping tubes in the IF and/or RF deck to get the best performance.
>> I think he suggested swapping specific pairs and moving through the
>> deck that way but I don't quite remember the process.
>>
>> There's a post in the Pearls dated Fri, 1 Apr 2005 23:37:52 EST from
>> Roger that touches on this but I'm not sure that's what I'm thinking
>> of.  I may be thinking of just a process for the RF deck's mixers and
>> not the IF deck but, again, the memory is distant.
>>
>> Anyone know what I'm talking about and, possibly, familiar with that
>> process?
>>
>> Thanks,
>> Barry - N4BUQ
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