uTracer (Micro Curve Tracer)

[rogb]

Hi everyone, just been getting my uTracer running again!
It's working well with all the 12A*7s and power tubes, despite not liking being closed in its tight fitting box.
I just leave it opened and it's fine.

I have a bunch of EF86 to test and really having a problem with the pinouts,
I just can't get it to run. Too many Screens and Grids it seems. I've tried working from my EL34/6V6 setups but it doesn't seem to work when I transpose the pinouts.
Has anyone got a working .UTS file for the EF86 please?

[martin manning]

Are you tracing curves or doing quick test? Quick test will give crazy results if you have oscillations going on, so it's a good idea to try tracing first. this is especially true of pentodes. I have had success placing a big ferrite on the grid patch cord to cure this, see examples here:
https://ampgarage.com/forum/viewtopic.p ... 97#p371097
https://ampgarage.com/forum/viewtopic.p ... 83#p378883
https://ampgarage.com/forum/viewtopic.p ... 84#p276084

[rogb]

Are you tracing curves or doing quick test? Quick test will give crazy results if you have oscillations going on, so it's a good idea to try tracing first. this is especially true of pentodes. I have had success placing a big ferrite on the grid patch cord to cure this, see examples here:
https://ampgarage.com/forum/viewtopic.p ... 97#p371097
https://ampgarage.com/forum/viewtopic.p ... 83#p378883
https://ampgarage.com/forum/viewtopic.p ... 84#p276084

No it works fine with all other tubes, I just can't connect the EF86 correctly, I am doing something wrong with my connections, I don't use QT much,
I just want to trace them. I have got ferrites all over the circuit

[martin manning]

Have you connected G3 to K (pin 8 to pin 3)? You could also connect the shield (pin 2 or pin 7) to the cathode as well. That is the internal shield, not the G2 screen electrode.

[rogb]

Have you connected G3 to K (pin 8 to pin 3)? You could also connect the shield (pin 2 or pin 7) to the cathode as well. That is the internal shield, not the G2 screen electrode.

Thanks Martin.
Could you give a rundown of the pinouts? That would help a lot.

I have connections A G S H HK K on my uTracer.
I'm pretty sure the pinouts are OK now but the trace doesn't seem right.

ef86.jpg

[martin manning]

Like this:

[martin manning]

Try I(Vs, Vg) with Va, Vh constant, step Vs from 60 to 180, Vg from -8 to 0, Va = 250.

[rogb]

Try I(Vs, Vg) with Va, Vh constant, step Vs from 60 to 180, Vg from -8 to 0, Va = 250.

Thanks Martin, you won't believe it, I had the pinouts right, but thanks for your clear graphic!
Heater fuse had blown so no heater voltage initially, doh!

Does this look right to you now, seems low, I thought EF86 went up to 15-20mA?

ef86-2.jpg

[martin manning]

Looks low to me too. The data sheet says at 140V Vs and -2 Vg, Ia is 3 mA, where you are showing 1 mA.

[rogb]

Looks low to me too. The data sheet says at 140V Vs and -2 Vg, Ia is 3 mA, where you are showing 1 mA.

I had 3 old Mullards and an EH. Looking at the datasheet, it looks like up around 10mA is the place to be. Pretty easy to see the best one now, which is why I have a tester.
Really appreciate all your help Martin.

Mullard 1.jpg

Mullard 2.jpg

Mullard 3.jpg

EH1.jpg

[istealth]

Hi All,

Probably it will be of interest to those who own the uTracer but also to those who would like to do a modeling of tube and trying different load lines. Some time ago I wrote an interactive web-based software for the uTracer, which can control uTracer over Wifi using ESP32. My small hobby project went a bit further and I also wrote a javascript tool for analysis of the tube data acquired using the uTracer which can plot the load lines and also produce the Spice models. Ronald mentioned that tool in his blog in the "Lab Notebook". I host the tool at http://utracer.live and at the Roland's blog you can find some links to the screencast, but here are some screenshots. You can also upload you own data there and try to play with it. I hope it will be useful for some other people as well and I would also be happy to hear some suggestions.

[turbofeedus]

Back working on the utracer, been getting some oscillations on pentodes (EF86, EL84, etc).
Any recommendations on where to start hunting down the gremlins?
I've got the 5V filament supply disconnected, and I'm using a bench PSU for powering the filaments. Am I making a mistake by not disconnecting the green wires from the screw terminals?
Should I put ferrite beads on the wires (red, yellow, blue, black) bringing the test voltages up to the banana jacks?
I know a grid stopper is recommended, just wondering if there's a less invasive fix I should try first?

utracer -8.JPG

utracer -9.JPG

[martin manning]

I'd try adding a snap-on ferrite to the grid patch cord, maybe plate and screen too if that doesn't do it. See here: https://ampgarage.com/forum/viewtopic.p ... 84#p276084, here: https://ampgarage.com/forum/viewtopic.p ... 97#p371097, and here: https://ampgarage.com/forum/viewtopic.p ... 83#p378883

[turbofeedus]

I'd try adding a snap-on ferrite to the grid patch cord, maybe plate and screen too if that doesn't do it. See here: https://ampgarage.com/forum/viewtopic.p ... 84#p276084, here: https://ampgarage.com/forum/viewtopic.p ... 97#p371097, and here: https://ampgarage.com/forum/viewtopic.p ... 83#p378883

Thanks Martin, I'll grab a couple of those and give it a try.
Here is an EL34 plot

EL34 oscillation.bmp

It's like it wants to do it, but there's obviously problems at the lower plate voltages .

[Murrayatuptown]

Thanks for the uTracer thread reference. Still looks appealing to me...

I, too, endured punch cards, for one college class decades ago...Watfiv mutant of Fortran.