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 but after a signal bump would come on. When the channel failed completely, I did what we do these days, I “googled” it. I found a few forums on which folks wrote of similar issues. I acted in direct accordance with Andrew’s note on this page. I did not replace the Caps.
Similar repair inquiry at the Alesis support blog – Read more…
What I did to repair my RA-500:
- Remove top cover of the amp
- Used my phone to take pics of the cable positions
- Removed the main PCB and de-soldered the relay, and replaced it with a new NTE R25-11D10-12.
- Put the amp back in the rack and cranked it up.
I’m not certain as to whether the backup amp sounded measurably worse or if the sound coming out the RA-500 pre-repair was that bad, but this thing sounds great now and you can beat repairing a $500 amp for less than 20 bucks.