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F5Turbo Illustrated Build Guide
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Old 11th September 2018, 09:40 PM   #461
Zen Mod is offline Zen Mod  Serbia
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F5Turbo Illustrated Build Guide
for 28V5 rail (and you'll get something as Vac x1.25 , when PSU is loaded ) , use 15K up to rail , 10K down to GND

remember that you don't need making heaters of cascode bias net resistors ......... so no need for so low value as you suggested
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Old 11th September 2018, 09:49 PM   #462
kpsthakur is offline kpsthakur  India
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Quote:
Originally Posted by Zen Mod View Post
for 28V5 rail (and you'll get something as Vac x1.25 , when PSU is loaded ) , use 15K up to rail , 10K down to GND

remember that you don't need making heaters of cascode bias net resistors ......... so no need for so low value as you suggested
O o forgot the current part... thanks Zen, will work on these values
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Old 12th September 2018, 06:24 PM   #463
kpsthakur is offline kpsthakur  India
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Quote:
Originally Posted by Zen Mod View Post
for 28V5 rail (and you'll get something as Vac x1.25 , when PSU is loaded ) , use 15K up to rail , 10K down to GND

remember that you don't need making heaters of cascode bias net resistors ......... so no need for so low value as you suggested
Hi Zen, how much difference will it make if i keep both the resistances 10K, since the potential divider will just half the input voltage, in my case around ~14 V, guess that should work just fine
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Old 12th September 2018, 06:54 PM   #464
Zen Mod is offline Zen Mod  Serbia
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yes , even if I like them slightly cooler
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Old 12th September 2018, 07:03 PM   #465
kpsthakur is offline kpsthakur  India
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yes , even if I like them slightly cooler
So 15K is final...cooler, and splits the rail into half
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Old 12th September 2018, 07:14 PM   #466
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I meant - cooler JFets
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Old 13th September 2018, 04:44 AM   #467
sangram is offline sangram  India
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The Toshiba JFETs operate at lower noise when the Vds is lowered below 12V.

15k/10k combo would be absolutely perfect at ~28.5V rail, I would run them a little lower actually maybe 18k/10k.
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Old 13th September 2018, 06:25 AM   #468
kpsthakur is offline kpsthakur  India
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Got it sir
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Old 24th September 2018, 08:19 PM   #469
esprit is offline esprit  Europe
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Well there is something I am just not getting !!!. as I still cannot get a logical result from the formula =

rail volt /(R26+R28)*R28= cascode voltage

please what is *R28

(my rails are 34.5)
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Old 24th September 2018, 08:22 PM   #470
6L6 is offline 6L6  United States
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Click the image to open in full size.

There is one error in this schematic - R26 should be 10K

Original documentation here -

http://www.firstwatt.com/pdf/art_f5_turbo.pdf

Last edited by 6L6; 24th September 2018 at 08:24 PM.
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