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Old 11th March 2012, 08:03 PM   #111
mogliaa is offline mogliaa  United Kingdom
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Quote:
Originally Posted by avincenty View Post
You have an issue with the DC offset of the Clock? Is it constant? If it is constant the counter should not care. On my setup I do have a DC blocking cap before my grid driver, otherwise it screws up my negative bias control.
Is the grid signal that drifts now (up and down randomly and slowly). It can drift 0.5v or more. I need to measure the output of the counter to identify where does it start drifting....
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Old 11th March 2012, 08:05 PM   #112
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Alfredo,
Those are brilliant curves. Really like it.
I did some plots as well for the 26 DHT with starved filaments. Check the 26 DHT preamp thread...
Cheers,
Ale
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Old 11th March 2012, 09:02 PM   #113
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Quote:
Originally Posted by mogliaa View Post
Is the grid signal that drifts now (up and down randomly and slowly). It can drift 0.5v or more. I need to measure the output of the counter to identify where does it start drifting....

Not sure if i makes a difference. But on my 4520 counter I ended up placing a 100uf in parallel to the 100nf cap right at the VDD pin.

Alfredo
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Old 11th March 2012, 09:08 PM   #114
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I can try that and see if it makes a difference. Drift appeared when I added the 100k resistor to the 1uF cap, albeit stability is great now!
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Old 12th March 2012, 01:25 AM   #115
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I hope you can get it to behave.

I took a quick video of the control of the steps per family using the LM339 comparator.

Video showing control of steps per family
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Old 12th March 2012, 07:58 PM   #116
mogliaa is offline mogliaa  United Kingdom
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Great video. traces are very clear indeed. PS: also liked you record cleaning machine btw

Hopefully I get time over the weekend to try to fix the stability issue
cheers,
Ale
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Old 17th March 2012, 06:57 AM   #117
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Default 12BY7A trioded curves

Click the image to open in full size.

Click the image to open in full size.

100mv=10ma
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Old 17th March 2012, 06:52 PM   #118
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Default 6EB8 Triode Curves

Thanks Gootee, I requested the changes as you suggested.

I am reposting the pictures with the correct title on them. I noticed something, the curves are very similar (almost identical) to the 12By7A trioded curves

Click the image to open in full size.

Click the image to open in full size.

100mv=10ma

Last edited by avincenty; 17th March 2012 at 06:56 PM. Reason: added voltage to current equivalent
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Old 17th March 2012, 06:55 PM   #119
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Default 25F5A trioded curves

Click the image to open in full size.

Click the image to open in full size.

100mv=10ma

Last edited by avincenty; 17th March 2012 at 06:56 PM. Reason: added voltage to current equivalent
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Old 18th March 2012, 12:44 PM   #120
mogliaa is offline mogliaa  United Kingdom
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Hi Alfredo,
They look really neat. Well done!
Attached is my latest test. 4P1L triode-strapped - one of my favourite tubes. It's really linear as you can see. Superb valve!

I managed to get a Beckman Industrial analogue oscilloscope in very good state for only 20 although it costed me more the train ticket to go and collect it

I suspect that the stability issue may be related to the regulation of the back to back transformers as it appears when I measuring a valve under large anode current. Need to investigate a bit.

Will add the decoupling electrolytic to the +5V rail and probably change the PLL components as suggested in previous posts.
Will report progress later
Attached Images
File Type: jpg 4P1L curves.JPG (34.8 KB, 53 views)
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