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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 25th Nov 2004, 1:57 am   #41
AC/HL
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Default Re: Thyratron pulse generator (for Sam)

There was someone on Ebay selling 10 EB91s recently. I didn't see the result, but chances are they'll be back soon.
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Old 25th Nov 2004, 1:38 pm   #42
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Default Re: Thyratron pulse generator (for Sam)

Once I have had a good look at the thyristor circuit, I will decide. I don't suppose increasing the valve-count will matter too much now. This thing will be huge anyway! Wonder where I could put it when it is finished!

I will try and update my site next week. I have been meaning to put the Wynn-Williams circuit in with the explanation of how it works!

Thanks for checking out that transformer. I hope I don't reach 100A for the heaters!

Sam
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Old 13th Dec 2004, 10:17 am   #43
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Default Re: Thyratron pulse generator (for Sam)

Does anyone have more comprehensive data on the EN91 than the basic data sheet?
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Old 13th Dec 2004, 11:27 am   #44
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Default Re: Thyratron pulse generator (for Sam)

Hmm. That would be handy, if anyone knows where they may be. My plan was to try and plot out the control curve more accurately myself when I got home. Maybe avearge six to ten different Thyratrons' results. Get them for some of my other types too. See what fun I can have with 6K25's! I only have a copy of the Brimar and the Mullard data sheets too (thanks Joe!).

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Old 13th Dec 2004, 12:09 pm   #45
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Default Re: Thyratron pulse generator (for Sam)

Quote:
My plan was to try and plot out the control curve more accurately myself when I got home.
I have been trying this but it is proving rather tedious mainly because the EN91 is very sensitive to tiny variations in electrode voltages. It doesn't behave at all like other thyratrons I have used - and definitely not like the type with actual grids. Early results suggest that the trigger point really doesn't change much with anode voltage (its about -2V for Vs=0), but the screen has more of an effect.
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Old 14th Dec 2004, 10:12 pm   #46
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Default Re: Thyratron pulse generator (for Sam)

A very rough guide for EN91 seems to be the trigger point is about " -10s-2 " where s is the screen voltage.
So we have a huge variation in the trigger point for quite a small screen voltage, e.g. -10V on the screen sets the trigger point to about +100V.
I measured this at Va=200V but the anode voltage doesn't seem to change things very much.
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Old 14th Dec 2004, 10:17 pm   #47
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Default Re: Thyratron pulse generator (for Sam)

There is a very comprehensive set of data in the RCA manual (the one that runs to about 6 volumes of loose leaf), which I saw at the last Harpenden, unfortunatly, it went for around £40, which was more than I was prepared to pay for a set of scruffy data books.

Anyone own up to having outbid me ? (or having a copy of their own).

Jim
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