Niketouille
Well-known member
Hi guys,
Currently I have a Crown DC300A on the bench.
Voltage doubler was dead because of dead caps.
Currently it works almost properly and I am able to trim the output offset voltage but :
- output signal is a bit noisy without load and with level pot CCW, about -70dBu 20-20k. On the scope it looks like psu spikes.
WIth level pot CW noise rise to -60dBu 20-20k.
Manual gives me at least 110dB S/N with level pot CCW. So with 33dBV max output it is almost in the ballpark... almost !!!!
- the output of the aop is stuck at about -0.5V. One of the schematic show a value of 1.35V. I already changed the aop twice and it doesn't change anything.
Also the problem is exactly the same on both output. I already changed Q1, Q2, Q101, Q201, changed electrolytics but not the big ones. Also both psu rail have a 50mV rms ripple without load.
I checked internal voltage, +5, +10, -10; +/-60 and +70. All ok but 60 and 70 are a bit off, something like 66V and 56V.
Is there someone who has an idea ???
Currently I have a Crown DC300A on the bench.
Voltage doubler was dead because of dead caps.
Currently it works almost properly and I am able to trim the output offset voltage but :
- output signal is a bit noisy without load and with level pot CCW, about -70dBu 20-20k. On the scope it looks like psu spikes.
WIth level pot CW noise rise to -60dBu 20-20k.
Manual gives me at least 110dB S/N with level pot CCW. So with 33dBV max output it is almost in the ballpark... almost !!!!
- the output of the aop is stuck at about -0.5V. One of the schematic show a value of 1.35V. I already changed the aop twice and it doesn't change anything.
Also the problem is exactly the same on both output. I already changed Q1, Q2, Q101, Q201, changed electrolytics but not the big ones. Also both psu rail have a 50mV rms ripple without load.
I checked internal voltage, +5, +10, -10; +/-60 and +70. All ok but 60 and 70 are a bit off, something like 66V and 56V.
Is there someone who has an idea ???
