[Milsurplus] Testing 1625s

[J. Forster]

Because I'd prefer to avoid collateral damage to the equipment, if the
tubes are bad.

-John

============



> Other than using a power tube in its intended circuit and comparing
> results between a known good tube and unknown one all other test are
> questionable at best. Mutual conductance tube testers are better than the
> Emission types that are almost useless but with power tubes there is no
> substitute for running it under power. I have used TV-7 that for some
> reason has the reputation for being the greatest tube tester ever, have a
> TV-10 in the shop now that I use for checking and matching tubes and had
> some experience with the TV-2 maybe the most complex and confusing tube
> tester built but today my favorite tube tester is a archaic Weston OQ-3 or
> civilian model 788. The question is other than if you just want to check
> tubes and put them up on the shelf why don't you just go ahead and try
> them in what you're going to use them in and see if they work or not?
>
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Ian Wilson
> Sent: Tuesday, October 04, 2011 11:25 PM
> To: jfor at quikus.com
> Cc: milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] Testing 1625s
>
> Volume 6 Number 3 of GE Ham News:
> http://n4trb.com/AmateurRadio/GE_HamNews/ge_ham_news.htm
>
> ..has a handy power oscillator circuit that I've found to be a good way to
> get a go/no go check
> on all sorts of power tubes. You will want a variable supply for this.
> Start
> at 100V or so on the
> plate and look for oscillation on a scope loosely coupled to the tank. You
> can ramp up the
> plate voltage and look for ionization (gas), etc.
>
> A simple Hartley will work with triodes and tetrodes with a dropper
> resistor
> from B+ to the screen in
> the latter case. Component values are highly non-critical: you want enough
> feedback to get the
> thing oscillating. My benchtop lashup (pictures suppressed for the
> squeamish) takes off somewhere
> around 15MHz.
>
> 73, ian K3IMW
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