I replaced the triac with similar rating and same symptom. Runs perfectly smoothly, bypassing the control pcb, feeding 60V,.15A DC bench ps. Pot and Rs ok, DB3 diac tests ok dropping +/-30V on droppered
35V supply. Even checked the switch current carrying . Just leaves 2 caps, that I've not ESR'd or LCR'd yet. A better triac match required?- posted
8 years ago