4p1l and djvu curves help please?

jack · Post by **jack** » Sat Apr 06, 2013 2:29 pm

Did some runs with Vs = 80V and Vs = 150V. Compares well with those in the Vademecum.

Compared two used tubes - have two more to compare with if necessary.

Vh = 4.2, Ia from 0->300V, Vgs from -8->0V

Paul Barker · Post by **Paul Barker** » Sat Apr 06, 2013 2:35 pm

Looks good. You must be very happy with the curve tracer.

jack · Post by **jack** » Sat Apr 06, 2013 2:51 pm

Paul Barker wrote:Looks good. You must be very happy with the curve tracer.

These particular curves were done at the request of another member - the main use for me is in matching - just in these two tubes there is an Ia variation of about 7%...

IslandPink · Post by **IslandPink** » Mon Apr 08, 2013 6:45 pm

These are brill, thanks Nick . I'm not overly concerned about a 7% variation in Ia, myself, I would be happy to check a few in my circuit and get a similar pair . Luckily they are very cheap valves ( at the moment ! ) .

As per my PM ( just sent - but now I've found the relevant thread ) , I could put in a few requests .... if you have time soon, or in the future , entirely up to you :

(i) Can you clarify where the G1 bias voltage is measured from - the upper or lower end of the filament, or the centre-tap ?

(ii) It would be good if you could change the Max dissipation curve to represent the Pa ( max ) for the anode alone, in pentode mode, which is 7.5W , not 9W .

(iii) On the G2 = 150V plot , for one of your valves, could you add a couple more curves for -9, -10 , & poss -11V on G1 ?

(iv) If you could do another plot for G2 = 105V , to represent another VR-tube option, that would be fab . G1 from 0V to -8V would be ideal on this one .

That would complete all I need to know about this valve

Thanks again .

jack · Post by **jack** » Tue Apr 09, 2013 3:24 pm

IslandPink wrote:(i) Can you clarify where the G1 bias voltage is measured from - the upper or lower end of the filament, or the centre-tap ?

The uTracer disconnects the filament from the heater supply and grounds both ends in the millisecond before taking measurements - this ensures there is no impact from using AC vs DC heating or voltage gradients - the thermal lag of the element is such that disconnecting the supply for that 1mS has no effect on the heater emission.

(ii) It would be good if you could change the Max dissipation curve to represent the Pa ( max ) for the anode alone, in pentode mode, which is 7.5W , not 9W .

Will do - trivial change

(iii) On the G2 = 150V plot , for one of your valves, could you add a couple more curves for -9, -10 , & poss -11V on G1 ?

Will do - again trivial to implement

(iv) If you could do another plot for G2 = 105V , to represent another VR-tube option, that would be fab . G1 from 0V to -8V would be ideal on this one .

Will do by the end of this week...

jack · Post by **jack** » Sat Apr 13, 2013 7:47 am

New graphs as requested...

IslandPink · Post by **IslandPink** » Sat Apr 13, 2013 2:53 pm

Superb ! Many thanks -

I've been doing some Spice sims of the 4P1L pentode as driver, they are looking good . Will put these up on the KR300B XLS thread soon .

jack · Post by **jack** » Tue Jun 04, 2013 2:53 pm

There is a new GUI for this tube tester that fits curves to the plot results then spits out an LTspice model that matches it.

https://docs.google.com/file/d/0B_sTLle ... N0NzA/edit

Not tried it yet, but a cool idea - I can measure an actual tube, then use its characteristics directly in LTspice...

IslandPink · Post by **IslandPink** » Tue Jun 04, 2013 5:39 pm

Hey , that's a bit of alright, isn't it ?
There are some jolly clever people out here !

IslandPink · Post by **IslandPink** » Tue Jul 23, 2013 6:23 pm

I wonder if I can entice any of you uTracer fellows to re-visit the 4P1L for me ?
James D told me you can sharpen-up the 'knee' of the pentode curves by putting about +40V on the G3 instead of tying it to the cathode.

Is it possible to do this, & can anyone have a go ?

If possible I'd like to see the curves similar to the above plot with G2 at 150V as a priority, because I might do the hardware mod some time in next week or two to see how it sounds.

Paul Barker · Post by **Paul Barker** » Tue Jul 23, 2013 6:36 pm

Those valves are at the lockup which is a few miles away. Hopefully I should be able to pick them up tomorrow. I can put +30v on with ease. That should be close enough, can also try it negative relative to cathode to see what that does. I seem to recall that for triode connecting the 813 which also g3 is not internally connected a negative g3 voltage was recommended by someone.

jack · Post by **jack** » Tue Jul 23, 2013 8:00 pm

Paul - can you do these if you have the tubes - I'm buried in work at the moment.

It'd be interesting anyway to see if your curves match mine.

Cheers

JamesD · Post by **JamesD** » Tue Jul 23, 2013 8:05 pm

Umm... +40 V on G3 is appropriate for some power valves such as PT15, etc. It might be a bit much for 4P1L...

I would suggest starting at +5 and use 5V intervals...

I've seen a few valves tweaked like this - the most recent is the PL802 where it really sharpened the knee almost to a right angle...

J

Paul Barker · Post by **Paul Barker** » Tue Jul 23, 2013 9:15 pm

nickds1 wrote:Paul - can you do these if you have the tubes - I'm buried in work at the moment.

It'd be interesting anyway to see if your curves match mine.

Cheers

No problem

IslandPink · Post by **IslandPink** » Tue Jul 23, 2013 9:57 pm

Thanks Paul - much appreciated - but any time in the next week or so will be fine .

audio-talk

4p1l and djvu curves help please?

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