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jarthel 30th May 2006 12:39 AM

help in adjusting Vout in the power supply of the "Brute force in a line stage" by Er
 
this is the circuit

I need some help in adjusting the Vout as I'm going to use the power supply schematic for another circuit.

transformer would be 250-0-250. rectifer would be 5V4g. And the desired voltage would be 150V.

I got a feeling it has something to do with the zener as 6 51V Zener is close to the +310V in the output. But can't figure out how the resistors come into place.

Thank you for the help.

analog_sa 30th May 2006 06:35 AM

The resistors play no role. They set the current through the zeners which is not critical within wide limits. Just get a combination of zeners with the approximate voltage you need.

Reading a basic electronics textbook won't hurt either.

jarthel 30th May 2006 06:38 AM

Quote:

Originally posted by analog_sa
The resistors play no role. Just get a combination of zeners with the approximate voltage you need.

Reading a basic electronics textbook won't be bad either.

which i'm doing right now. reading on the principles of zener diodes. :)

but you can't expect someone whose hobby and main job is not electronics/electrical circuits to know it all at once :)

Thank you for the help. :)

analog_sa 30th May 2006 06:43 AM

Quote:

Originally posted by jarthel



but you can't expect someone whose hobby and main job is not electronics/electrical circuits to know it all at once :)



Views may differ here. Relatively high voltages demand that you know what you're doing.

jarthel 30th May 2006 06:46 AM

I have conducted electrical/electronic experiments in the university as part of my comp eng degree. even made a robot as our thesis.

as such I am not really a newbie.

but sadly my line of work since graduating in 1994 has been in software/systems development so my knowledge is very rusty :)

rpapps 30th May 2006 07:07 AM

2 Attachment(s)
Hi jarthel
You are on the right track.
Just remove three of the zener diodes to achieve the 150 volt output that you want. The resistors are so conservatively rated that no other changes are necessary.
Output should now be approx. 150 volts, not 310 as shown.
Cheers
Rob

jarthel 30th May 2006 07:13 AM

Quote:

Originally posted by rpapps
Hi jarthel
You are on the right track.
Just remove three of the zener diodes to achieve the 150 volt output that you want. The resistors are so conservatively rated that no other changes are necessary.
Output should now be approx. 150 volts, not 310 as shown.
Cheers
Rob

Thanks for the help.

Is there an advantage to using 1x 150V zener VS 3x 51V zener?

Thanks very much

rpapps 30th May 2006 07:26 AM

High voltage devices tend to produce higher levels of random noise. The addition of the noise from three lower voltage devices should give a lower total level but, in practical terms, probably not a lot of difference.
Having said that, what are you going to use it with?
Cheers
Rob

jarthel 30th May 2006 07:38 AM

in this power supply circuit, can I omit R5 and R6?

rpapps 30th May 2006 07:47 AM

It depends on how you are going to use it.
Tube experts correct me if I'm wrong but I believe that the reason for positive bias on tube filaments is to reduce hum.
If this is not a consideration then by all means remove R5, R6 & R7.
Cheers
Rob


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