Thursday, 14 January 2016

Alesis RA-150 amplifier repair

Some months ago i bought a pair of passive Tannoy Reveal monitor speakers and a Alesis RA-150 off eBay Kleinanzeigen (kinda craigslist but with less stupid advertisements), both several years old. I plugged everything in, turned it on and was disappointed because there were short cut outs, sometimes on the left, sometimes on the right. After some research I found out, that most of the RA-150 sooner or later get this problem and it's because of a crappy relay from the company Dong Woo (titled Dog Poo in one comment :D ). So I ordered a new one (decided to take a Omron g2r-2a 12vdc bc it was cheap) and switched it. It took me some time but that was definetly worth it. Now the system is running without any problem. If you have the same problem, here's a detailed guide:

  • Unscrew the screws on the top and take the panel off. Now it looks like this. The Dong Woo relay we want to switch is located on the middle PCB with the 2 big capacitors. It's the black box up right behind the cable. Right from the amp lies the new relay.

  • Most cables on this PCB can be disconnected, which is our next step. But we should remember wich cable belongs to which plug
  • Unscrew the three screws on top of the PCB and the one that is down under the case. There is also a female screw on top of this screw
  • Now we can turn the PCB around, maybe we'll have to cut some zip-ties so that the cables are not in our way. The component that is held by the female screw has thermal paste underneath. We just wipe this away with a cloth. Now we place the PCB so that we can work on the back:
  • The relay is now located down left. I marked the 8 joints (mad paint skills, bro!). Only 6 are used, but we just desolder all 8 and put all pins from the new relay in. As the two pins we don't need are not connected to anything, this is no problem

  • Now we heat our soldering iron and desolder all 8 joints. If we worked correctly, we can pull the relay out with a little more force. Then we put the new relay in and solder all 8 joints. We should be careful that we don't create joints we don't want to have, so be calm
  • We need to apply thermal paste to the component where we removed the old paste
  • Then we put in the screws again and connect all cables we disconnected
  • The last part is screwing the panel on again. But before that we may want to check if everything works. So we connect everything and test it
  • We are done! Depending on what replacement relay we chose, we spent a few bucks and maybe one or two hours of time.
Maybe I can help someone with this step-by-step tutorial.
By the way, the amp and the monitor speakers are pretty decent for the price I paid ;)
See you next time. Rock on!

Hello World!

Hi! I'm setting up this new blog to spread cool tips and tweaks related to audio engineering and guitar stuff and to show you some examples from my work as a "professional amateur". I will only post something if I feel I have something important to say, so sometimes it will be more, sometimes less. Feedback is always appreciated. That's all for the moment. So long and thanks for all the fish!