Tascam 644, group not working

[hscheer]

Hi,
One of the groups (group 4) on my midistudio 644 is not working. At first i considered the possibility of a loose wire, but I couldn't see any upon inspection. All the other groups work fine. Has anybody else run into this problem, and if so how did you solve it?

 

[shredd]

Functional problems that exceed my technical diagnostic/repair skills are entrusted with an authorized service tech. Solves it every time.

 

[Jack Saturn]

It could be any number of things, like a faulty component or small crack in the path of that group. Do you have access to the schematics in the service manual?