Looks like the transformer is dead, Jim.
Transformer show 83vac open circuit, 0 vac when connected to the pcb.
Bridge recifier output: -1.3 vdc. Replaced the bridge rectifier thinking it could be defective, but the condition persists.
R1: 69.6 KΩ
Voltage at C1: -1.3 vdc as expected.
Re-winding the oscilloscope transformer may be an option (there are very experienced technicians at the city who make their living from that). But they will charge at minimum $50.000 COP, when the whole unit costs 200.000 COP.
I'm thinking about getting a separate transformer, not very easy due the required specs: 120 vac In, 135 vac Out.
Or maybe a DC-DC converter, hooked up to the working 100 vdc circuit?
Is worth mentioning that the pcb tracks are very flimsy and tend to separate from the pcb easily. I shouldn't trusted the hippie who sold me this oscilloscope