uTracer (Micro Curve Tracer)

[martin manning]

Hi Aleks, it's built-in. So far I only know how to get one measurement variable (here Ia) out at one shot, but it came out just like you see in the Excel table. I'd like to find a way to get it all at once and avoid having to merge multiple data files.

[martin manning]

Here is another test result from the same tube. I've figured out how to dump the entire data set and get it into Excel (turns out it's easy).

This comparison shows how this EH 6V6 matches up to the GE data at 250V Vg2 and matching Vg1 values (uTracer is limited to eleven curves in one test).

The EH tube's emission is 10% high across the board as previously shown, but here the screen current has been added and plotted along with the anode current. The screen current level matches quite well at the spec point, but the anode current knee and consequently the break in the screen current curve are quite a bit sharper than the original. What this means to tone quality, I don't know.

It will be interesting to try some other brands, some preamp tubes, and some NOS tubes and see how close they come to contemporary published data. Of course I'll have only a small sample size, and the old data was gathered using less sophisticated analog equipment, and it was reduced and hand-plotted by a draughtsman using a french curve...

[JazzGuitarGimp]

So Martin, does the uTracer have the ability to plot curves for posative grid voltages? And if so, does it also plot the grid current? It would be nice to be able to do plots for grid voltages of +1VDC to say, +10VDC in one volt increments with grid current.

[martin manning]

Yes and yes, but for triodes only because the screen supply is used to produce the positive grid voltage.

[JazzGuitarGimp]

I've been really intrigued by class AB2 for the past year or so. Unforunately, I'm not real interested in triode output stages. Is there any way you can see to "beat the system"? Maybe power the screen from a separate, HV bench supply?

[martin manning]

I've been really intrigued by class AB2 for the past year or so. Unforunately, I'm not real interested in triode output stages. Is there any way you can see to "beat the system"? Maybe power the screen from a separate, HV bench supply?

It may be possible, but I don't don't know, as the normal mode of operation is that the voltages are pulsed and the measurement values are grabbed on-the-fly in milliseconds, which is how the tube can be operated above its maximum plate dissipation.

[Structo]

Martin did you use a RS232 interface to your computer?

[martin manning]

I'm using a USB-to-RS232 converter, but I've also been through four of them to get a couple that work. One of them looked good in preliminary testing, but failed a later test where the software actually tried to communicate with the PIC controller. Another user has it working wirelessly with an added Bluetooth module- something I want to look into as well.

[martin manning]

Another run with the same tube, triode-connected this time. Interestingly, in this configuration the test result agrees very closely with the GE data. This leads to the conclusion that the difference between this tube and the GE is in the screen, since it is taken out of the picture in this test.

[VacuumVoodoo]

Not bad, not bad at all. My AVO MKIV is a cool looking machine but a bit of a pita in use. This looks like a good alternative to consider.

[martin manning]

IMO vintage testers are like vintage cars: ok for a hobby and sunday driving, but limited in capability, not good for frequent use, and collectors are driving prices up.

[martin manning]

Some progress on this after a long delay in selecting and procuring hardware. The chassis is a pre-finished Hammond enclosure.

There is still internal wiring to do, but the mechanical assembly is complete. The patch-cord photo shows a mock set-up for a 6V6GT. I think I now have a solution to the computer interface that I like, bypassing the RS232 I/O and going directly to the controller's transmit and receive pins with a USB-TTL adapter cable. Still working on a way to run the GUI SW on my Macbook.

[M Fowler]

Nice Martin your too smart. I was just impressed with the colorful display let alone the technical know how to build this and operating skills.

[martin manning]

Not me... The smart guy is the architect R Dekker. I'm just the decorator.

[Colossal]

Freakin' sweet Martin. I've had one of those on my growing To Build list.