DIY Curve Tracer

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Ex-Moderator
Joined 2011
Gents,

Thanks, I could not have done it without your help. As for the arcing, I think it was a separate issue, since the problem did not show up until recently... It was the sloppy construction and the poor choice of the mini-banana jacks that caused the arcing, but I think it had nothing to do with the interference problem I had/have. Even now, in order to get really clean traces, I still have to run the tests during non-business hours.:mad:

Jaz
 
Ex-Moderator
Joined 2011
Have you tried a mains filter yet?

Yes, I did, it did not help... I think I should put the whole thing inside a well shielded chassis - it would be an improvement for sure... Also I am still having some issues with the grid drive, it seems that at the low grid stopper settings (<10k), there's still some parasitic oscillation, it just bugs me that a simple circuit is giving me so much grief :rolleyes: I did a lot of things trying to remedy the problem - short, thick signal path, ferrite beads on the leads, regulated supplies... but still not quite there...

Jaz
 
Ex-Moderator
Joined 2011
Ale,

Yes, I have tried to isolate the problem using other circuits (both battery and bench supply powered), so far, I am pretty sure the issue is limited to the adapter itself - a combination of the circuit topology, wiring, construction & layout. I have other circuits running without problem, since I have used such point to point wiring in the past many times successfully and followed the standard practice for grounding and routing... but I am sure I missed something along the way, just need to track it down and fix it...

Jaz
 
Ex-Moderator
Joined 2011
Anyone has experience with the 6P15P (or 6n15n)? The only way I could make the pentode curves match those in the datasheet was to connect the suppressor grid (g3) to the control grid, when I connect the g3 to the cathode (as it would be in most circuits), I get strange looking curves.

G3-G1 on the left, G3-Cathode on the right:

An externally hosted image should be here but it was not working when we last tested it.


TIA,
Jaz
 
Ex-Moderator
Joined 2011
Gents,

I am now on the road, so can't work on the adapter... Another bit of info: I also ran tests on some EL84s, which has the g3 internally connected to the cathode, all the other test conditions were the same, and I had no issue with the curves - they were exactly how they should be based on the datasheet.

So I am puzzled as to why grounding the g3 externally to the cathode would be an issue with the 6P15P. Not floating the screen supply can distort the reading but not the shape of the curves, right? :confused:

Thanks,
Jaz
 
Ex-Moderator
Joined 2011
Hey Jaz,
First of all: happy New Year! Hope you had a good time.
Here is the 6P15P pentode trace with 150V screen bias. G3 is connected to cathode and screen supply is floating with return to the cathode (I have my sensing resistor in the cathode).

6P15P Pentode | Bartola Valves

Ale,

Happy New Year!

As usual, great looking curves! Will try and find out what's wrong with my setup or tubes (they are Chinese, not even the Russian ones...)

Cheers
Jaz
 
Ex-Moderator
Joined 2011
Jaz,
Can you post an example of a pentode trace that works for you and how are you connecting each element and power supplies?
Thanks
Ale

Here is the test setup and result for the 6P14:
An externally hosted image should be here but it was not working when we last tested it.


I think I also isolated the cause of the problem with the 6P15 - it seems that the screen grid is drawing a lot of current so the supply goes into current limiting, and there is also parasitic oscillation present - this is the first tube that I am having problem with, will investigate further...

Thanks,
Jaz
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.