For some odd reason my -20V rail suddenly dropped to -13.5V. I couldn't find the culprit by looking for a heat source

The PCB has those solder bridges on the voltage rails. -20V gets split into A, B and C. With the bridges you can cut out rails

The fault is definitely on rail B. My solution was to feed this rail not from the internal supply but from my lab supply, to then pump more current into it and to hopefully find the culprit through its thermal emissions. Can't find it tho :/

The thing does oscillate now. This is constant frequency mode, not the sweep. So something is really wrong in the control section

Would someone please gift me a thermal camera 👉👈

The wobbliness reacts to percussion. Cold solder joint, bad contact, a transistor or IC with broken bonding.

On our way to Eurofurence