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 3rd September 2006, 10:31 AM #1 wrangler   diyAudio Member   Join Date: Aug 2006 Tubes power supply 220 t0 300V ? Who can help me change the output power of the last fet channel for mij tubes amp from 220 to 300V see drawing. Thanx in advance.
Alain Dupont
diyAudio Member

Join Date: Sep 2003
Location: Paris - France
wrangler,

Your last 2 regulators are referenced from:

R19 / R28 then a RC including R21 / C37 provides a slow turn-on
So you'll have to change R28...

You have to be sure the voltage on Q7/Q8 is 20 to 30 volts higher, about
330/340 volts if not ...

To do so measure the voltage at the connection of R19/R21.

R19 + R28= 1.5 MOhms current = 340 V/ 1.5M = 0.226 mA
Voltage ref = 0.226 mA * 1MOhms = 226 Volts
New value = 305 Volts ==> i= 0.309mA ==>
R19 = 100 KOhms ======> That changes the output voltage on both Q7/Q8

Then if you want to change only the output voltage on Q7
you have to put a voltage divider with 100K / 1M Ohms and a RC just before R25.

Alain.
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wrangler
diyAudio Member

Join Date: Aug 2006
Quote:
 Originally posted by Alain Dupont wrangler, Your last 2 regulators are referenced from: R19 / R28 then a RC including R21 / C37 provides a slow turn-on So you'll have to change R28... You have to be sure the voltage on Q7/Q8 is 20 to 30 volts higher, about 330/340 volts if not ... To do so measure the voltage at the connection of R19/R21. R19 + R28= 1.5 MOhms current = 340 V/ 1.5M = 0.226 mA Voltage ref = 0.226 mA * 1MOhms = 226 Volts New value = 305 Volts ==> i= 0.309mA ==> R19 = 100 KOhms ======> That changes the output voltage on both Q7/Q8 Then if you want to change only the output voltage on Q7 you have to put a voltage divider with 100K / 1M Ohms and a RC just before R25. Alain.
Thanx you have bin very helpfull.

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