[Milsurplus] Testing 1625s

[Ray Fantini]

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