Richard, You R391 is mostly an R390 you can use the R390 TM 11 5820 357 35 manual and TM 11 5820 357 -35P parts manual. There is a R391 manual that covers the receiver and auto tune operation and theory. But I do not know the manual numbers. Several of the Fellows on the reflector here have R391's and can help you with specific questions. Roger AI4NI