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Old 30th June 2004, 09:03 AM   #11
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Join Date: Feb 2004
Location: Portugal
Question VR tube spice model

HI,

I'm considering building a (not so) similar power supply for use with a 811-3 amp. The design uses a couple of voltage reference tubes and has a B+ of 800V.
However, I have this silly idea that I must thouroughly simulate everything in spice before I even order the parts. The problem is I can't find a spice model for a gas tube anywhere, so I'm considering switching to zeners ... Any ideas ?
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Old 30th June 2004, 09:48 AM   #12
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Join Date: Jan 2003
Location: Sweden
Hi Paracelsus,

Why dont you make a model of a VR tube using a Zener model. Most data sheets for VR tubes have information of regulation which would give you dynamic resistance. For capacitance I think you need to guess but it should not be so difficult. When you make the model of the VR tube you will find that dynamic resitance is much less than for a Zener of similar voltage and if you measure noise you will find that also noise is much less in the VR tube.

I work a bit different from you, I calculate all by hand first, then I usually build the circuit and measure it to find out if it behave as it should, after that I model the circuit in Spice and have a hard time adjusting the individual models so they fit reality, I have found that especially tube models usually are very bad and all the models I use I have modified after measuring on real circuits. Sometimes I also do some initial modeling in Spice to test some crazy idea but if i am going to build something I usually calculate it trough by hand before building it in order to avoid any problems.

Maybe I should also mention that I enjoy the kind of math that is involved when designing tube amps. I would probably use Spice more if I could get better tube models and/or if I was doing commercial design but even then I would do manual calculation for sanity checks.

Regards Hans
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Old 3rd July 2012, 02:22 AM   #13
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Join Date: Mar 2012
Quote:
Originally Posted by ErikdeBest View Post
Hi all

I built the showed regulated PS using ECL82 and two 62V zener diodes stacked aiming for 300VDC. I'm getting about 70VDC out of it.

I measured 20volts between pin 8 and GND. I assume this must be the problem (shoulf read 124V). With the 100k potentiometer I can adjust the output between 60 and 80VDC, exactly 1/4 of the range recommended for 120V of zener (240 till 320VDC).

I connected two 1k2 resistors to the "heater bias", each one going to one of the fillaments.

Have you got any opinions what van be wrong here?
Dear ErikDeBest
I am writing to you as I myself built the same regulator. I aqm having the same problem you had with output voltages. I got 50 to 60 Volts at the output of the regulator. I wonder if you may share the solution to this problem. I checked and re cheked all connections and proper values of resistors etc. All attempts have been unlucky so far. Kind rgrds. Stefifiun (Italy)
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Old 3rd July 2012, 05:36 PM   #14
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Location: Near Eindhoven, the sanctum of the pentode. and among that other things.
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i always pick up some 85A2 when im at hamfests funny little things most of the times i can get 5 for 1


the next one is 3 months away from now. Il scoop up some more.

there are 6W glass passivated zeners those can peform the same job.
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