5v333
Well-known member
hi!
i have done a somewhat simpel rectification/regulation circuit for the plates of my stereo tube amp for my passive eq.
secondary winding: 180VAC 100mA
rectifier bridge (4 x uf4004)
filtering: 2 x 100uF
MOSfet regulation: 240Vzener (filtered with 47uF) biased IRF740 (capable of a LOT of A and W)
outputvoltage expected: 235-240V
load: about 35mA per channel
i have only one side hooked up while trying to make final adjustments/tests of the tube circuits.
before i had one tube biased a little cooler and have been kind of fine with supply voltage.
but now i see that the dc get lowered from about 235V to around 220-230V and isnt very stiff as i think it was before. dont know if this is after rising bias on one tube from 24mA to 32mA or if something broke down. when doning sweeps i get an assymetric square wave on the output with a rounded rise and a small overshoot on the fall part. bandwidth is about half i had before...
would you think my mains transfomer is to light for me? even if it is stated to deliver 100mA at 180VAC.
i can see that the zener reference is getting messed up if the raw dc starts to fall but is my load of 35mA enough to cause this..?
if i pull the output tube the supply is around 250VDC.
ive checked some parts for faults but havent find anything yet...
also been thinking about adding a transistor and small resistor on the output for current limiting.
any suggestions about this?
i have done a somewhat simpel rectification/regulation circuit for the plates of my stereo tube amp for my passive eq.
secondary winding: 180VAC 100mA
rectifier bridge (4 x uf4004)
filtering: 2 x 100uF
MOSfet regulation: 240Vzener (filtered with 47uF) biased IRF740 (capable of a LOT of A and W)
outputvoltage expected: 235-240V
load: about 35mA per channel
i have only one side hooked up while trying to make final adjustments/tests of the tube circuits.
before i had one tube biased a little cooler and have been kind of fine with supply voltage.
but now i see that the dc get lowered from about 235V to around 220-230V and isnt very stiff as i think it was before. dont know if this is after rising bias on one tube from 24mA to 32mA or if something broke down. when doning sweeps i get an assymetric square wave on the output with a rounded rise and a small overshoot on the fall part. bandwidth is about half i had before...
would you think my mains transfomer is to light for me? even if it is stated to deliver 100mA at 180VAC.
i can see that the zener reference is getting messed up if the raw dc starts to fall but is my load of 35mA enough to cause this..?
if i pull the output tube the supply is around 250VDC.
ive checked some parts for faults but havent find anything yet...
also been thinking about adding a transistor and small resistor on the output for current limiting.
any suggestions about this?