Potterton belong to Baxi - Baxi might supply you with an intsallation and fault finding guide for your boiler - I doubt they allow the PCB drawings into the public domain.
The part number you quote is a Siemens number LMU30.211B159. - Potterton's number for this is 5112178.
Electrolytic capacitors are the weak link - see this repair story on an older Potterton boiler...
http://kaijaks.co.uk/blog/nick/2008/02/10/dodgy-old-boiler
Good luck...
Peccavi
November 2010
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