EAR 834 Integrated tube help needed

Hi,

Its a long story but I am trying out a EAR 834 integrated tube amp and upon arrival I am having a problem where the left channel is working but the right channel is not on the EAR 834 Tube Integrated.

I checked the speaker, cd player, interconnect cables, and speaker cables and they all work fine.

I then thought I would try swapping the preamp tubes from left to right. However, I dumbly pulled out the tubes not remembering whether the ECC83 or the ECC85 preamp tubes go in the back sockets or the front? I mistakenly thought they were all the same tubes. Anyway, Can someone tell me the respective position of the preamp tubes for this amp.

thanks

Michael