PDP-8/M power supply questions

I've just started the rebuild of one of my PDP-8/Ms. This is an early machine with the power supply mounted on the left of the chassis. One potential problem I am slightly concerned about is that the front two power transistors have been desoldered and removed. Does anyone know if these are a vital part of the PSU and if so what the part numbers are so I can try to source replacements? You can see a picture here http://www.pdp8.co.uk/ (enlarged view here http://www.pdp8.co.uk/files/2009/03/00016.jpg) If anyone else has a PSU of this type, could they take the opportunity to take a few pictures for me. Would be really useful to have another reference source for the rebuild. All the best, Toby -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.