I wrote this post because other people have complained of the same issue. There are a couple other incomplete posts on the WWW about it. I hope this helps.  Repair Alesis RA amplifier - All right channel output ceased. I use an Alesis RA-500 to drive Alesis Monitor 1 MKII studio monitors here on my desk. I purchased it second hand and have used it regularly since 2009. Recently all output ceased form the right channel. In retrospect, this issue had been manifesting itself for a year or so. The channel would intermittently not "start" with the amp's power up [...]