LA120 PSU fault

I'f I'm reading the printset (on bitsavers) correctly, it appears there were 2 versions of the PSU. The older one used a constant-voltage-transformer ('CVT', ferroresonant transformer) and a PCB containing some regulators for the +5 and +/-12V lines. The later version was a switcher. The printset contains the scheamtic of the switcher and of the PCB for the older version, but for some reaso nthe CVT circuit is not there. In both cases, the +12V line is produced from the +24V line by a 7812 regulaotr, so if you're missing the +24V line, it's not surprising that the +12V line is missing too. Ifyou have the switcher, there's a not a lot that can remvoe the +24V line. An open-circuit rectifier would be the most likely problem I think. If it's the CVT, then I would guess the +24V line is obtained by rectfying and smoothing a secodary winding on said transformer, so again I'd check the rectifier. Trace the +24V line backwards to find it.

I just hope it's not transformer trouble!

-tony