1 meg seems a bit low, but not unheard of. The rails are more of a concern. It looks like they should be +/- 27 VDC, so you've got some investigating to do. I'd be worried about the transformer. If the diodes are OK, and the filter caps are OK, the transformer is suspect. Is anything getting hot? Diodes or caps? Does the transformer get hot, smell or make any noise? You might have to pull and measure the secondary leads, which according to the schematic should be 20 VAC. Anybody got other suggestions?