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Old 24th November 2012, 10:14 PM   #341
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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.

Jaz
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Old 25th November 2012, 08:59 AM   #342
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Have you tried a mains filter yet?
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Old 26th November 2012, 06:22 AM   #343
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Quote:
Originally Posted by mogliaa View Post
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 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
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Old 26th November 2012, 08:57 PM   #344
mogliaa is offline mogliaa  United Kingdom
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Do you get same interference when using the scope measuring low level signals? Try a simple oscillator from a 9V battery and see if it is the noise also coming on your scope. Just a thought to try isolating the root cause...
Ale
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Old 27th November 2012, 01:05 AM   #345
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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
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Old 27th December 2012, 06:28 AM   #346
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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:

Click the image to open in full size.

TIA,
Jaz
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Old 27th December 2012, 11:33 AM   #347
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the datasheet specifies 150v on G2 for these.

what g2 voltage are you testing at ?
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Old 27th December 2012, 12:01 PM   #348
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Quote:
Originally Posted by v4lve lover View Post
the datasheet specifies 150v on G2 for these.

what g2 voltage are you testing at ?
Tested with 150V on g2, did I overlook something? Why can't g3 be grounded on this tube?

Last edited by jazbo8; 27th December 2012 at 12:06 PM.
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Old 27th December 2012, 01:22 PM   #349
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G3 MUST be grounded indeed.

It looks like if you measured the cathode current (i.e. anode + G2 + G3) rather that anode current alone ? ? ?

Yves.
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Old 27th December 2012, 02:37 PM   #350
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If you're sensing current on the cathode return then g2 supply has to be floating with return on the cathode, otherwise you will sense anode and screen current
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