Angstrom 200 Preamplifier balance adjustment

I used this preamp for quite a few years with several  good amplifiers such as Ayre V3, Mark Levinson 27, etc. and found it to be excellent for my listening tastes. When I started using a tube integrated amp I stored the Angstrom for about a year. Because the speakers I’m using are very inefficient, though, (82-84dB) the dynamics are limited by the 40 or 80 WPC output of the amp, I purchased a Lexicon 225 amplifier to use with the Angstrom to see if that combination would be acceptable. The problem is that the signal from the preamp now is not evenly balanced with one channel’s volume at least 50% lower than the other. I seem to remember that there is a balance adjustment capability but it requires access to the menu and the output from the Angstrom is RCA and the TV has only HDMI inputs. Before I go deeper into this I’m hoping that someone here has knowledge on this subject or can direct me to a source to find an owners manual. Thank you