sure looks like the LRE LR-5555 (A), i.e., the Setton RS-440.
Not sure if that's helpful or not, but it seemed worth mentionin'.
http://audiokarma.org/forums/index.php?threads/lafayette-lr-5555.503093/#post-6531233
LR5555A by Mark Hardy, on Flickr
Setton RS660 RS440 by Mark Hardy, on Flickr
Hard to tell without a schematic.. If its anything like the 5813 the volume potentiometer R-Ch is miss tracking or still dirty ...
sure looks like the LRE LR-5555 (A), i.e., the Setton RS-440.
Not sure if that's helpful or not, but it seemed worth mentionin'.
http://audiokarma.org/forums/index.php?threads/lafayette-lr-5555.503093/#post-6531233
LR5555A by Mark Hardy, on Flickr
Setton RS660 RS440 by Mark Hardy, on Flickr
Yes, the Viking is pretty much a Lafayette LR-5555 and Setton 660 (the Setton has a protection section the other two do not).
The Lafayette (and possibly the Viking) are known to have problems with the off/on/speaker selector switch. Not sure if that has anything to do with the OP's problem, just that it's a known weakness.
The Viking has it's own ON/OFF Switch seperate from the Speaker selector