Guru
Joined: 21/06/2018
Location: AustraliaPosts: 1191
| Posted: 09:22am 09 Jun 2024 |
I believe that is the problem it is noise pick up under U1 & U2. Rather than you mount a whole metal plate, can you fabricate a small copper foil shield that covers the underside of U1 & U2 and the D1, D2 & D3 about 40mm square at a guess and soldered to 3 or 4 earth points 5-6mm clearance is fine. It does not have to be real pretty just avoid the mains connections and check clearance between other points and the shield and that nothing squashes it against other soldered points when you install it.
I would like to make an observation that it would have been better mounted to the side of the main switching parts or at least have a metal shield the same size as the board if you are going to mount it so close to the noise - I have never tried doing that.
The only way that the servo loop can be happy with less volts at the feedback point is if injected noise is adding to the feedback volts causing the voltage at A0 to be the same for the cases of 230V & 214V. More load = more noise - reduce output voltage a bit to be in balance again.
Edited 2024-06-09 19:36 by wiseguy