Your schematics are not accessable unless you’re a vcf member. The rigol outputs look like there no rectification going on as there’s both a positive and negative going wave.
Where did you attach the scope probes? And can you make the schematic available to the genetic public? Sent from my iPhone > On Aug 28, 2025, at 23:26, Robert Jarratt via cctalk <[email protected]> > wrote: > 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_Operation_Nov84.pdf. > 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-1299248, > 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-output.png > > 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-output.png > > Do these look correct? The peaks seem to be too low to even begin to produce > the required output voltage. > > Thanks > > Rob
