datong uc-1 hf/vhf converters

hi i have a datong uc-1 hf/vhf converter the2 meter converter works very well but the hf does not i can get a very weak signal from my rf sig gen but no receive signals the frequency trimmers are correct using my frequency counter and i have the manual for this converter but nothing found any ideas i will  be  free over christmas thanks for looking any info would be great sty safe do radio paul m0kbd 73s

Datong made some interesting kit back then, not up to Mutek standard, but interesting all the same. There's a set of manuals etc at https://sites.google.com/site/datongarchive/uc1/uc1-manuals if that helps?