Re: Test equipment

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

Uhhh... why would one need high voltage from your oscillator, other than to
make up for low sensitivity of some other measurement tool, or if one were
making measurements on some voltage sensitive device that needed a HV swing.
For a linear device (like a TC) it shouldn't make much difference.

If you need higher voltages you could use a transformer.

I grant you that some tube output souces are more "rugged" than some older
solid state sources or might have better stability characteristics (hence
the popularity of McIntosh amps in research labs to drive all manner of
inductive loads (like small shaker tables).. transistor amps (ca 1960s and
1970's) used to be very, very picky about the output impedance and would
tend to oscillate).  However, modern solid state drivers are pretty tolerant
of unusual loads.

The one place where a tube would hold a clear advantage would be in a high
power (hundreds of watts) high frequency application (>100 kHz) where the
appeal of "one big tube" is very apparent.  Another place would be where the
inherent damage immunity to small transients or a high radation environment
(sold state devices do tend to have a problem with radiation, both in a
total dose sense, and in a single event effects sense).

Testing a TC doesn't fall into one of these cases.

Another, probably more relevant situation, is where you are buying old
surplus equipment.  A surplus something from the 60's based on tubes is more
likely to still be working than a surplus something based on transistors,
because of the general novelty of transistors in that era.  However,
anything built after the 80's (and there is a ton of it available surplus
these days) is probably better as solid state than tube.  The only gotcha on
newer stuff is that, by then, a "consumer market" for test gear had arisen,
so you have the problem of generally cheap gear with smaller design margins
and less inherent reliability.  There wasn't any appreciable demand for
cheap, mass market test equipment in the 50's and 60's, and whatever had
been produced then has long since died. (I don't see many folks
recommending, for instance, Eico brand gear...)

Finally, one can go out today and buy, brand new, a fairly decent function
generator for around $100 that will probably outperform, in general, some
tube gear from the days of yore. More to the point, that new unit will use a
lot less power, be easier to lug around, and probably be more stable (and
remain reasonably in calibration).  Sure, one can make very fine
measurements with a Wheatstone bridge and a optical galvanometer, but I
suspect that most folks just use that $30 DMM.

But, on the other hand, it's just a hobby, and if you want to work with 30
year old test gear as part of the enjoyment, then more power to you.  I have
friends who forge iron and steel with tools little changed in the last 2000
years, and derive great satisfaction from it.  Sure, they could just buy the
gate hinges and stuff, but that takes the fun out of it. One of the younger
engineers at work scrounged up a slotted line (and the probes) and I have to
confess it was kind of cool to make the measurements and go through the
process (and of great pedagogical value), but, from a "getting the job done"
standpoint, the automated network analyzer is a faster tool, and produces
more accurate results to boot.

I'm sure that for the amount of money I'm thinking about spending on lathes
and mills for home, I could probably buy all the machining I'd really do for
the next 5 years, but, there is a definite satisfaction in "doing it
yourself".  Perhaps it's because I work in electronics for a living, but
somehow, the appeal of working with old test gear isn't there. (Big
caveat... if you are capital limited (aren't we all..), then you can make
the trade of hobby time for capital.. old gear with lots of work requires
less capital than new gear...)


You have decide how you want to spend your coil working time.


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, December 15, 2002 12:07 PM
Subject: Re: Test equipment


 > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<dhmccauley-at-spacecatlighting-dot-com>
 >
 >
 > That is an untrue statement.  The HP 200x Tube Audio oscillator is still
one
 > of the best audio oscillators out there primarily because its one of the
 > only
 > ones I've ever seen to put out high voltage.  (High voltage meaning
greater
 > than 30VAC in this case)
 >
 > Dan
 >
 >
 >
 >  > Tube audio oscillators have no unique virtue that I can see, unless
 >  > it's that the are old and hence inexpensive.  As for the ESI bridge, I
 >  > think I saw one at C&H Surplus' Pasadena store a few weeks ago.  Look
up
 >  > "C&H Sales" on Google and go to their "online store" or whatever they
 >  > call it.  Since I already have one I didn't look at the price, which
 >  > with those guys may be anything from good to very high.  They are
always
 >  > subject to bargaining if you show up in person, but that probably
 >  > wouldn't be very convenient for you.
 >  >
 >  > Ed
 >  >
 >  >
 >  >
 >  >
 >  >
 >
 >