Drawing Valve Plate Characteristic graphs

[guitarmike2107]

Has anybody got any tutorials/ info on drawing plate characteristic graphs for different screen grid voltages? or are these found through testing only?

Thanks

Michael

[guitarmike2107]

Ok, after a little bit of reading RDH4, I guess I am asking for a clear instruction on using valve conversion factors.

Anybody?

[zaphod_phil]

...or are these found through testing only?

I suspect that's the case. For a good example, see www.freewebs.com/valvewizard2/ef86.html for some EF86 curves you won't find published in any spec sheets.

[guitarmike2107]

Not sure if this makes a difference but I don’t think I clarified my question properly, what I meant was to redraw the plate characteristics graph by extrapolating from an existing graph.
RDH4 talks about conversion factors to do so, guess I will just have to go and read and then re-read that section a dozen times to get an understanding.

Mike

[katopan]

I'd be interested if you work it out. Have always thought that you'd need to test to obtain the curve at a different screen voltage to what is shown on the data sheets.

[guitarmike2107]

Well I am pretty sure this can be done now, if you have RDH4 look at page 40 in section 2.6. only problem is you need a plate characteristics
graph for zero bias and multiple screen voltages, this seems hard to find at the moment, but I am pretty sure If I could get some graphs I could set up a spreadsheet to automatically redraw graphs based on new screen voltages.. Think I will e-mail JJ

[Merlinb]

An article from 1950 on the subject: http://www.freewebs.com/valvewizard2/De ... istics.pdf

[Shrapnel]

... but I am pretty sure If I could get some graphs I could set up a spreadsheet to automatically redraw graphs based on new screen voltages.. Think I will e-mail JJ

Ooooooh, that would be so nice... something that has all the specs for various g2 (suppressor screen) voltages and g1 (control grid) voltages and plot them for you, based upon your choice of g2 voltage.

probably a lot of work to do, but in the end, it would make design so much easier as you can then play around more than a pre-made graph would.

[guitarmike2107]

... but I am pretty sure If I could get some graphs I could set up a spreadsheet to automatically redraw graphs based on new screen voltages.. Think I will e-mail JJ

Ooooooh, that would be so nice... something that has all the specs for various g2 (suppressor screen) voltages and g1 (control grid) voltages and plot them for you, based upon your choice of g2 voltage.

probably a lot of work to do, but in the end, it would make design so much easier as you can then play around more than a pre-made graph would.

Exactly what I am thinking, I need to go read the article Merlin posted as it may have some helpful info, I know that it can be done with some patience and allot of work.

No luck from JJ yet on the screen voltage characterics graph, I have found one for a 6l6GT but other than that they seem sparse.

I get too easily distracted.. I am meant to be building amps!

[zaphod_phil]

An article from 1950 on the subject: http://www.freewebs.com/valvewizard2/De ... istics.pdf

Thanks - that's a very interesting article.

[katopan]

Great article. Thanks Merlinb.

[Art_Stanton]

Has anybody got any tutorials/ info on drawing plate characteristic graphs for different screen grid voltages? or are these found through testing only?

Thanks

Michael

You don't have to completely redraw plate characteristics yourself, you
can use the already published info and curves on the datasheets.



For example in JJ6L6GC datasheet if you want to get g1 curves for g2
voltage of 300V, find a point from the transfer characteristics curves
where Ug2 = 300V and Ug1 = 0V, then draw a straight line from there to
the plate characteristics curves of Ug2 = 400V. From this you can see
that your new Ug1 = 0V curve for g2 voltage of 300V is the old Ug1 = -8V
for g2 voltage of 400V. Your new -4V curve is the old -12V curve, new
-8V is the old -16V curve and so on. This is not 100% accurate but close
enough.

Alternatively you can use proper datasheets like General Electric
datasheets. In GE 6L6GC datasheet there are g1 = 0V curves for different
g2 voltages. To these curves you can normally plot your loadlines and
then use transfer characteristics curves to plot your bias point.

[plodd]

I tried using Art_stanton's described method to work out some 6V6 characteristics. My problem was that JJ 6V6s have a spec of 500V but the JJ datasheet only shows transfer characteristics to 200V. They also only show plate characteristcs for triode connection.

Does anyone know if there is a pentode plate characteristics on the JJ 6V6?

I have tried using old 6V6GT data and extrapolated (guessed) Ug2=300 and 350 for Ug1=0. The old datasheets only show plate characteristics up to Va=285V. So I extrapolated (guessed) new grid curves higher than the previous g1=0. I also had to keep extending the original graph (gridpaper) as I was drawing well above it.

I will be using approx 420V B+. I feel that this method of extrapolating 3 variables (transfer, plate char. grid lines and the actual gridpaper) is too much guessing. Is there any other way?

[naciketas]

You could try with an emulator software, a lot better than guessin'

http://www.duncanamps.com/spice.html

Bye

[plodd]

I have tried battling with LTspice, and i lost. I've got no idea what to do with the sim.
Can it simply be used to draw plate characteristcs? I have the software and 6v6gta .inc file. I just don't know what to do.

[zaphod_phil]

Simulations are only as good as the device (or tube) models being used. We have no idea who accurate the 6V6 model may be, especially in regions which go outside the original specs. So I wouldn't hold a lot of store by what a simulator will give you.

[naciketas]

I too needed some searchin' to begin, found some advice on ax84's forum.
All you have to do at first is :
1 draw a circuit for that particular tube
2 start the sim (a new graph window will open)
3 use the instruments

Try this link:

http://www.ax84.com/bbs/dm.php?thread=366494