External Floppy issues

Hi All,

My a1200 will not see my external floppy drive. The drive works fine on my a500.
I get a red screen on bootup (well, it's more like orange), but the machine continues to boot and operates fine apart from the external floppy drive.

I have a HxC Floppy emulator in df0:. If this is configured for a single drive, df1: is totally dead. If the HxC is configured for 2 drives, the external df1: will spin and access when I access the df1: on the HxC (it does not read anything, as I guess its trying to read from both df1:'s!). What this says, I am not sure, but it kind of suggests that maybe the external df1: is just not being detected.
If I replace the HcX with an internal floppy, df1: is dead.

I read somewhere:
U8 send all the control signals(motor, disk selects,head step + direction etc)
U7 reads it's status(write protect,disk change, ready etc.)

which suggests to me that my U7 may be bad.

My 2 CIA's are both 391078-01 chips. I can get hold of some 391078-02 chips, which from my understanding are 2Mhz instead of 1Mhz.

Can I replace just one CIA with a 391078-02? or will I have problems if the CIA's are different? I'm really not looking forward to having to replace either to be honest!

Or... am I barking up the wrong tree?

Any help will be greatly appreciated.

Thanks.