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Hoffman Amps Forum image Author Topic: fixed bias ?  (Read 2035 times)

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Offline shooter

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fixed bias ?
« on: November 17, 2016, 11:08:56 am »
Probably a slap me upside the head ? but...
If I have a 50VAC tap and I want 58vdc as center, my brain says a single diode - cap won't cut it, but a bridge plus fat cap would?
am I on the right page?

thanks as always
Went Class C for efficiency

Offline PRR

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Re: fixed bias ?
« Reply #1 on: November 17, 2016, 11:38:14 am »
The peak of a 50.0VAC wave is 70.7V. A simple diode and cap will catch almost 70V DC.

A 50K pot on top of a 100K resistor gives a range like 69V to 45V, with 58V nearly in the center.

Offline shooter

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Re: fixed bias ?
« Reply #2 on: November 17, 2016, 08:27:50 pm »
Quote
The peak of a 50.0VAC wave is 70.7V
thanks,
for some reason I thought bridge did the 1.414x, but single diode did .9x - makes life easy
Went Class C for efficiency

Offline PRR

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Re: fixed bias ?
« Reply #3 on: November 17, 2016, 10:54:52 pm »
Diode to cap is 1.4.

Diode to choke to cap is 0.9.

X2 or /2 depending how you count CT windings or doublers.

Offline shooter

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Re: fixed bias ?
« Reply #4 on: November 18, 2016, 08:36:19 am »
Thank you again, that nugget is now in my achieves!
I'll try and send you the 70 weather from here!!
Went Class C for efficiency

Offline PRR

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Re: fixed bias ?
« Reply #5 on: November 18, 2016, 03:39:01 pm »
> send you the 70 weather from here!!

Thanks. I'm hustling to re-hose my backhoe because the 50 degree weather is ending and at 40 degrees it gets tougher to work with old/cold fingers. I did put a washer pump in the Honda, but the plow-truck seems to have eaten another fuel pump.

Offline shooter

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Re: fixed bias ?
« Reply #6 on: November 18, 2016, 06:59:51 pm »
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gets tougher to work with old/cold fingers
uh huh!  you got 1-2 days then Canada is gonna add it's 2cents to our weather
Went Class C for efficiency

Offline pompeiisneaks

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Re: fixed bias ?
« Reply #7 on: November 18, 2016, 09:23:27 pm »
Not to derail this thread more, (ok nvm I am) but an old coworker lives in Upstate NY and its 72 there today :P

~Phil
--
Phil Davis
tUber Nerd =|D

 


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