[ARC5] When a "Good" Tube, Ain't- AN/ARC-2 Success (long)

millerke6f at aol.com millerke6f at aol.com
Fri Mar 21 14:15:22 EDT 2014


Many years ago I spent a few years taking care of a section of WU Telco's transcon Microwave System which made use of RCA  WLD-6   6GHZ tube based equipment  one of the features of this readio was a toggle switch on each assembly that dropped the filament voltage by 10 percent and it was indeed a great predictor of pending tube life.  These assemblies also featured metering for every tube and varactor stage as well so you could hold the switch down and take the meter readings in the reduce emission condition and take action if needed.  Another nice feature of this type of test was that it was non intrusive;  it didn't affect the transmission or reception to any degree therefore the system didn't take any hits.


But I still rely on a tube tester (TV-10 for performance) and a little Sencore Mity Mite for shorts and gas tests.


Bob, Ke6f



-----Original Message-----
From: Richard Knoppow <1oldlens1 at ix.netcom.com>
To: kgordon2006 <kgordon2006 at frontier.com>; Glen Zook <gzook at yahoo.com>
Cc: Arc5 <Arc5 at mailman.qth.net>
Sent: Fri, Mar 21, 2014 10:05 am
Subject: Re: [ARC5] When a "Good" Tube, Ain't- AN/ARC-2 Success (long)



----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "Glen Zook" <gzook at yahoo.com>
Cc: <Arc5 at mailman.qth.net>
Sent: Friday, March 21, 2014 9:00 AM
Subject: Re: [ARC5] When a "Good" Tube, Ain't- AN/ARC-2 
Success (long)


>> I do have several tube testers but seldom use any of 
>> them.
>
> Likewise here.
>
> Ken W7EKB

     I must disagree about the usefulness of tube testers, 
IMO they can be quite useful although, of course, the final 
test is if the tube works in circuit.
    Oscillator drift with filament voltage variation seems 
to be quite common. For instance, the SP-600- will drift 
quite noticeably with line voltage despite having a 
regulator in the B+. The regulator eliminates drift when the 
RF gain changes but does not affect filament voltage. The 
frequency moves slowly and will come back when line voltage 
comes back. I noticed this first when using a receiver on 
the same line as an electric heater with a thermostat on it. 
Some receivers have ballast tubes to regulate filament 
voltage to sensitive circuits.
    On a tube tester its interesting to lower the filament 
voltage a little and watch the meter. On a good tube the 
indication will usually go _up_ a little and then come down 
while on marginal tubes it just goes down. I am not sure of 
the mechanism of this test but it does seem to work.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com 

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