I have to say I am suspicious of the i.c, as initial comparisons between
the 2 modules don't show any notable differences in component values.
The i.c itself seems to handle virtually everything aside from the tuned
circuits. I am suspicious that I have 2 faulty chips, one with an RF
amplifier or AGC fault or something along those lines, the other with a
fault in the tuning section.
I may well see if I can grab the i.c. and try it if it's cheap enough.
It may be difficult soldering up since there are quite a few large
components around it, which may make access awkward.
Thanks for the info