spaghetti
Active Member
@MattiaM your analysis makes sense, so today I replaced temporarily the transistors on the PSU board with other similar ones, just to see if anything changed. I used some MJ for the TO220 types, and BC639/640 for the rest. Unfortunately voltages did not change at all.
I noticed that by replacing R407 (4.7ohm) with a slightly higher resistor (~6ohm) and voltages got much closer. I wonder if this modification may have some benefit or it's just pointless.
I'm getting ready for inserting the VFETs back in their sockets. Today I tried to add 68 ohm 5W resistors on +-53V rails in order to limit the current in case anything goes wrong, I noticed that on the negative rail I normally have -55V but now I get 52.5V. Not exactly sure why, but if I remove connector 1 (specifically the black wire, which is a ground connection) from the class B/Protection board voltage goes back to -55V.
I noticed that by replacing R407 (4.7ohm) with a slightly higher resistor (~6ohm) and voltages got much closer. I wonder if this modification may have some benefit or it's just pointless.
I'm getting ready for inserting the VFETs back in their sockets. Today I tried to add 68 ohm 5W resistors on +-53V rails in order to limit the current in case anything goes wrong, I noticed that on the negative rail I normally have -55V but now I get 52.5V. Not exactly sure why, but if I remove connector 1 (specifically the black wire, which is a ground connection) from the class B/Protection board voltage goes back to -55V.