Read 4.7 for the 723 regulator on DE boards here:
http://www.pinwiki.com/wiki/index.php?title=Data_East/Sega#Power_Supply_Issues
Covers voltage doubler section mentioned above. Due to its location, would be a good idea to replace C2 with a high temperature cap.
If you get an abnormal voltage on ripple voltage reading - retry measurement using an old fashioned analog meter. Some digital meters do a poor job with this sort of measurement and give you phantom readings. Can never get a phantom reading from an analog meter.