Simplistic Mosfet HV Shunt Regs - Page 61 - diyAudio
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Old 21st October 2009, 12:36 AM   #601
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Seems to be ok in test. Acted as you said, the voltage dropped a bit at first.
I have a 10K test-resistor. At 180V this gives me like 18mA trough it and 18mA shunt as I followed Salas scheme (p.53), I guess.

What I have calculated wrong is the input voltage. I thought it would come out 215V but ut is now 240V with the reg attached. I might be running the LEDs a little too hard. Should I adjust the LED-ground - resistor?
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Old 21st October 2009, 12:47 AM   #602
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Just run a bit more current, will be better for the reg and it will sag the trafo a bit. You have quite a sink there, so no problem. Change to a 47 Ohm R1 for about 42mA. The question is if your choke will saturate. How large in VA the TX is and what is its nominal secondary? I don't think you run em hard. What current you derive if you divide the voltage across their resistor to ground by its value?

P.S. You were about to run 2 regs? Then they will sag the secondary for sure. Still 70V is nice for driving faster rise time.
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Old 21st October 2009, 01:10 AM   #603
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tx is 100mA, have multiple sec on 180, 200, 220. (do not remember which one I use)
Valve rectifier
First cap is 12uF
Filter choke is 50mA, 700R
second cap is a 100uF

I need to cut the heatsink to fit it. Now I think no more than 35C.

234,4v/ 47k = 5mA - how does that sound?
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Old 21st October 2009, 01:14 AM   #604
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Spot on led current I wanted. Also your CCS current looks spot on. Its the leds are really 1.7V it seems. You brobably use the 200V one and your tube rectifier drops 40V. With just a few more mA in the shunt you probably going to make the rectifier duck a bit. Which double diode valve you use? Is it a stiff or limp one for voltage sag?
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Old 21st October 2009, 01:24 AM   #605
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It`s a 5z4g and I like the looks
The LEDs are red, thats what I`m sure of.
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Old 21st October 2009, 01:35 AM   #606
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OK thought of the solution. R1 = 47R 1W. First cap 6u8 to 8u2. In spec for longevity, plus it will drop some voltage. It does not seem to be losing much before you ask for 100mA at voltages you use. Is it a Brimar?
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Old 21st October 2009, 09:41 AM   #607
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Yes its a Brimar.
Can use 6uF (it is now 2x6u very large WW2 pio sprague). I`ll play around with the psu.
If I paralell the R1/56E with 293E I get 46,988E. Need to dig deep in my drawer and see what values pops up.
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Old 21st October 2009, 09:52 AM   #608
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Ballpark 40-50R will be adequate. It isn't that critical. Just see you don't go over 55c with your final sink, so to have it working reliably for long. The first CLC cap value is going to help you tune your input voltage. Aim for 50V Vdiff in out reg. You will use one shunt for 2 12+12ma bias asking channels?
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Old 21st October 2009, 10:10 AM   #609
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One shunt for two channels, yes.

I have one more print and next time I might expand to using two shunts for this preamp, but as for now one will do.
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Old 21st October 2009, 10:12 AM   #610
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Ok. Let us know your impressions soon. And remember, we always like to see nice pictures posted when glowing valves are involved. Good luck!
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