Thanks for the reply, mate. I tried some of your suggestions and discovered the following:
- Continuity was fine in the converter cable; pins 6 and 7 were correctly linking with pins 1 and 3, with pins 2,4 and 5 correctly connected.
- I tried the midi moose with my old D50 synth and it worked fine (9v PSU attached to the midi moose - see noted behaviour below).
- I then tried the midi thru on the MP-1 to the D50 and it also worked fine (9v PSU attached to the MP-1), however it also was working on the MP-1 too!
Having performed the last two steps above, the midi on the MP-1 now appears to be functioning as expected. I have no idea why that would have any effect and why it has "fixed" the issue. One thing I did note with the second step above, is that the first time I hit a switch on the moose when attached to the D50, the D50 would read "Midi communication error" (or something like that), but subsequent selections didn't show this error and changed the patch accordingly.
Well, the problem has righted itself for now, but I suspect it may rear its ugly head again in the future; watch this space.
Thanks
Bob