| wrangler |
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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| 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. |
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| wrangler |
| 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.
:) :) :) :up: :up: |
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