I managed to bring the scope home today and test some voltages, I don't have another scope so I measured VAC with a Fluke 75 (without true RMS) so hopefully multiplying by sqrt(2) gave the peak-peak ripple values, please let me know if this is wrong.
+180V = 184.3V (90mV pk-pk ripple)
-12V = -12.00V (200mV pk-pk ripple)
+12V = 15.6V (325mV pk-pk ripple)
+140V = 105.8V (110mV pk-pk ripple)
These results seem to confirm previous suspicions, the manual says 140V ripple is reasonable (although the DC is strangely low) but +-12V is way out (should be 6mV pk-pk) also the +12VDC is oddly high? So something is definitely wrong with the 12V rails.
I measured the drop across all directions of the bridges and seemed to be 0.49-0.56V. Is there any way to identify which bridge (if any) is faulty? Can the open circuit condition only occur whilst under load?
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif.pagespeed.ce.5xOqKkq0Co.gif)
Since they are only low voltage secondaries on the 12V regulator side I should be able to cobble something together with some 1N4001 to replace the faulty one at some point.
Attached are some pictures of the internal construction