Tubes?

[Jdo300]

Hey Guys,

I just finished building my tube circuit and before I fire it up (and hopefully not blow it up), I thought I'd take some before and after pictures. The circuit I made is going to be powered from my function generator and I will test it with square and sine waves. I'll let you know if something bursts into flames!

God Bless,
Jason O

[innovation_station]

nice work jason you waste so little time for you  i think your luck will be much and in a short time congrats on your chooise to use tubes



now how many more people can tubes rubb off on the more the better ~~~~~many hands light work~~~~~

ist

[Mannix]

Jason,
a better aproach is to mount the socket on a chassis so that your leads are short.
particularly the grid...read about the miller effect...same as mosfets.

The last of your trouble is blowing it up....thats for the silicone heads.

[Jdo300]

Ok Everyone,

I am officially sold on the tubes! They are sooo nice and smooth! Below I posted some scope shots of a square wave, sine wave, and pulse wave that I input into it with my function generator. I must say that my amplifier circuit sucks really bad because the waveforms are all badly distorted but  I was very impressed with the pulses this thing put out. For the negative pulses, I was able to swing 226V in only 230 ns! Just to give you an idea of what that means. Consider the MOSFET driver circuits we have been harping on for so long:

For my SS drivers, I was runing on 9V and was able to get switching speeds of 30ns on average with my IRF840 FETs. Slew rate is calculated by dividing the voltage gradient by the rise time (roughly) and gives you a way to compare different switching speeds and voltages. For my MOSFETs, the slew rate was 450 MV/s.

As for the tube (which by the way isn't even working at it's best yet). I swung 226V in 230 ns. The rise time may not seem like all that but the actual slew rate is 982.6 MV/s! Almost double the best time the MOSFET can do. And this is without even trying to make it work better!

Guys, the tubes are not that hard to play with. I for one just need a good  amplifier circuit to use since the one I made isn't so hot.

@Lindsay,

Yes I realize that having the tube floating in the air is a bad thing. I will actually build it into a nice project box setup as soon as I get the amplifier circuit I want working. For now ,I'm just experimenting with different configs to see how it behaves. The tubes that I supposedly have a bandwidth of 25 MHz which should be plenty to work the coils that I have.

I'm sold on the tubes now I just need to learn how to make 'em work for our purposes now.

God Bless,
Jason O

[innovation_station]

awsome jason i knew you would be

now afew words we should listen to the words of sauron i went digging and this is what i found

@sauron sorry to repost your words but it must be done

is

thease are saurons words from pg 40 of lotr thred

What is a valve?

Thermionic emission
Before transistors became common, all electronics relied
on the valve, there were even computers using valves!
All metals have free electrons within their crystal
structure, so some of them must be at the surface of the
metal, but they are bound there by the nuclear forces
between them and the adjacent atoms. However, the
atoms and electrons are constantly vibrating due to thermal
energy, and if the metal is heated sufficiently, some
electrons may gain sufficient kinetic energy to overcome
the attractive forces of the atoms and escape.

As a consequence of these escaping electrons, an electron
?cloud?, or space charge, forms above the surface of
the heated metal cathode. Once this cloud reaches a certain
size, it will prevent other electrons attempting to
escape from the surface because like charges repel, and
an equilibrium is therefore reached.
Some metals have stronger forces binding their electrons
than others, so stripping an electron from their surface
requires more energy, and the cathode has to be
heated to a higher temperature:

Melting point of pure tungsten: 3410?C
Pure tungsten cathode (transmitter valves and lightbulbs): 2700?C
Thoriated tungsten cathode (small transmitter valves): 1700?C
Oxide coated cathode (receiving valves): 1000?C

As can be seen, the operating temperature is sufficiently
high that the cathode could literally burn, so the structure
of the valve is enclosed in glass and the air is evacuated.
We now introduce a positively charged plate, or anode,
into the enclosure. Electrons will be attracted from the
cloud, and will be accelerated through the vacuum to be
captured by the charged anode, and thus a current flows.
The cloud has now been depleted, and no longer repels
electrons quite so strongly, so more electrons escape from
the surface of the cathode to replenish it. Current flow is
unidirectional because only the positively charged anode
is able to attract electrons, and only the cathode can emit
electrons. We now have a rectifier, but it requires rather
more than 0.7 V to switch it on; typically 50 V is needed.
In order to control current flow, we interpose a grid or
mesh of wires between cathode and anode, resulting in a
structure with three electrodes known as a triode.

If the grid is negatively charged, then it will repel electrons,
and although there is a space charge above the cathode,
no electrons reach the positively charged anode
because they are unable to overcome the repulsion of the
grid. The grid to cathode voltage Vgk therefore controls
the number of electrons reaching the anode, or anode current
Ia.

Mains borne interference is not a thing to be taken lightly.
Spikes of 1 kv and above are a common (in some areas frequent)
occurrence and this can and does damage unprotected equipment.

In addition to all man-made interference, there is another source
which will always be beyond any kind of legal
regulation and control ? the weather.
Electric storms and even lightning strikes make their presence
felt through the mains.