[cctalk] Repairing an Olivetti M24 PSU

My Olivetti M24 was humming away nicely until I switched it off. It then failed to power on again. The PSU is not outputting any voltages on any of its outputs. The technical manual is here https://bitsavers.org/pdf/olivetti/m21_m24/Olivetti_M21_M24_Theory_of_Opera…. The PSU is described from p188 with an outline schematic on p194. The full schematic is on p274. A schematic useful to anyone with the actual board in front of them has been created in the following forum post https://forum.vcfed.org/index.php?t...ower-supply-replacement.1237316/#post…, the schematic is this one: https://forum.vcfed.org/index.php?attachments/m24_psu_schematic-jpg.1252584/. I have done some verification with the scope but I have reached a point where I am not sure what signals I should expect. I have attached a dummy load on the +12V, +5V and +15V outputs to meet the specs for minimum current. I see a 20KHz square wave on the inputs to the output transformer T438 (pins 1 and 2). The manual says that the diodes on the output rectify a half wave. I assume these are the ones labelled D134 and D136. The following image shows the signal on the two diodes marked D134 on the schematic for the 12V output, measured from their anodes to 0V output. https://rjarratt.wordpress.com/wp-content/uploads/2025/08/diodes-on-12v-out… For the other two diodes, labelled D136 for the 5V output I get this: https://rjarratt.wordpress.com/wp-content/uploads/2025/08/diodes-on-5v-outp… Do these look correct? The peaks seem to be too low to even begin to produce the required output voltage. Thanks Rob