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Old 3rd September 2006, 10:31 AM   #1
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Default 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.

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Old 3rd September 2006, 12:22 PM   #2
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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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Old 3rd September 2006, 02:36 PM   #3
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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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