Question about Alesis RA-150 Amplifier
The amp works great for an hour or so then starts to crackle and cut out intermittently. Any ideas?
My Alesis SA-300 started the cutting out when at moderate levels some months ago... Well, Radio Shack has instant gratificaion for those who have one in the neighborhood. Part number 275-249 will do the trick!
I replaced the Dong Woo part with the Radio Shack item and the amp is back to its old self... maybe even a little better. Loud, clean and steady.
Thanks to all you who have contributed to this thread.
Posted on Jan 09, 2010
I had the same problem with my RA150.
Searching the net found Samson Servo 170 has same problem.
Further search reveals its exactly the same circuit as Alesis RA150 - Mmmm!!
the fix? change the relay on PSU board (the black boxrear right. It's a 12vdc double pole changeover type.
I used an Omron G2R-2A (only has the contacts that are used - has two pins missing).
Perfect amp now - very happy
Hope this helps someone else.
Posted on Sep 17, 2008
I had the same problem with cutting out. My amp is about 5 years old and the problem started about 6 months ago. I was sure the problem is with the relay that keeps the output switched off until the power is up and stabilized. You can hear this relay click a few seconds after you power up. It is the only non-solid state device in the audio chain so it is a logical suspect. Others have replaced it. I did a quick and dirty fix by drilling a 1/16" hole on two opposite corners of the top of the relay cover. I then shot some contact cleaner into one of the holes. If you do this, be sure to put a drill stop on your drill because you don't want it penetrating any deeper than the cover thickness, about 3/32". After that I reconnected but I have not put the cover back on yet. It has been working now for several days. When I am convinced it is now OK, I will seal the holes with a dab of silicon sealer and put it all back together.
Posted on Dec 11, 2008
I had the speaker relay problem with my RA-300 as described in these posts - intermittent output sometimes one or both channels. I was able to obtain the exact relay from a company in Dayton Ohio. It is Parts-Express (www.parts-express.com). The part number for the relay is: 075-128. Cost is $6.24. Unsoldering the old relay was a challenge, so make sure you have the proper soldering tools and experience before diving in.
Posted on Dec 29, 2009
Disgruntled Alesis owners....think you have problems... I have 30 of these amplifiers...
You may be interested to hear that there are at least two faults associated with the "dog-poo" (sorry Dong Woo) relays.
Crackly intermittent sounds on L/R (or both) is usually down to poor relay contacts.
I am also finding instances of intermittent relay operation whereby the relay clicks in and out for no reason. I have traced the problem to the actual relay coil (or internal coil connections).
I will break this latest one open tomorrow and see what's actually causing it!
Either way REPLACE with Farnell (Part No. 1329680).
Posted on Sep 07, 2009
REPLACE output relay with Farnell (Part No. 1329680).
Posted on Jul 15, 2010
For everyone who have this kind of problems with this series amplifiers of Alesis RA-150 -> RA-300.
I've just repared one by replaceing the cheap-*** OpAmp BA-4560 in the feedback circuit, it was feeling a bit hot too.
You can use any type of dual low noise Opamp (I used the LM385).
Greetings from Jonathan
Posted on May 09, 2009
I got no reply from Alesis, hmm I see...
Well I cracked into my RA300 the other day to check out the relay (black box, rear, main board, shirty2008 pointed out). I was instructed by an former co-worker that relay contacts in power amps sometimes arch and get burnt or pitted, usually from current moving through while switching poles. This happens when you have an input signal or music playing when you turn the amp on. His suggestion was to re-surface the contacts by running between them very fine emery cloth, 600 grit or so. I thought I'd try this and move on from there. While doing so I noticed a cap was scorched and coming apart. This was a green 2A104J polyester film type near where the power transformer (big heavy thing in the middle of the unit) connects to front of main board. I got a $2 four-pack of 104J caps w/ same specs and used one as a replacement; re-surfaced the contacts with $1 sheet of sandpaper and $5 can of contact cleaner from the electronics store. With the cap in place and a refurbish relay making sure all excess of cleaner was gone before putting the cover back on, WALLA she works like new! mmmhmm all tell hu what.
In conclusion I think: the relay was the problem, the capacitor a near future problem, and Alesis makes cheap chinese bukaki with the sin being lack of support for their products.
Posted on Dec 05, 2008
I have a RA300 with the same problem. Symptoms exactly as described by Blueshift and jdmille. It's definitely the crappy relay. I replaced it by a Finder 44.62.9.012 12VCD Coil 2x 10A changeover relay. It fits in nicely. The Amp works perfectly now.
Posted on Nov 30, 2008
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I mentioned in my previous post that Alesis have ignored all
my emails so I felt compelled to send them one final email and received the
“Sorry, this was the first email I have seen on this. Something must have been preventing it from coming through. We always strive for quick response times.
First, there are no 'mass faults' with the RA series amps. The forums can make anything seem widespread when it is only a handful of people. From your description of the sound cutting out, there are a few possibilities why this is happening.
If it cuts out completely, there might be a problem with the power supply to the amp. I would check your ground connection. This is something people often overlook. This may have come loose or is not providing an adequate completion of the circuit. If that is not your problem check your power cable. Also make sure you are using the proper gauge speaker wire, as recommended in the RA manual. If this does not help out, I would recommend this to be serviced. Our UK office can be contacted for assistance at 01252 341 400. I’m not positive on the cost for servicing, though our UK office will be able to provide this.”
I think I will try looking at the relay since others are reporting this is correcting the fault when replaced.
Posted on Dec 05, 2008
I have an RA500 with a similar problem - for a few months now, often the left channel would be "crackly" and cut out, but then seem to "warm up" and be fine. Now, the right channel started to behave like Blueshift's RA150, crackly and cut out. There's no problem with load; I'm using 6 ohm Polk Audio Model 11 studio monitors (circa 1982 and still some of the best speakers I've ever heard, IMHO). Note that these behaviors have nothing to do with volume, either - I typically run the amp's controls between 9 and 12 o'clock.
The amp is only about 15 mos old, so I wouldn't think caps are going yet from age, unless they were crappy to start with.
Posted on Jan 27, 2008
In the event that there are these kinds of problems by buildig up warmth its sometimes hard to find somewhere in electronic components, then you can search for a canister cold-spray to search for the place that could be having the faulty parts
Electronic repair dying art
Posted on Jun 24, 2016
OK, first of all, with a little research, you'll see that the REAL
reason for all the RA series amp failures are the crappy ****-WOO relays
Alesis chose to use. RA-150, 300, and 500 all have the same problem.
Simple solution for the RA-300 (providing you can solder/desolder or
have a friend who does):
* Buy one NTE R25-11D10-12 (at $6.24)
* Disassemble the amp (6 screws on top, and four on the side, inside the heat sink fins, the inside screws)
* Carefully unscrew the power supply board (it's the one on the bottom with 4 screws and one screw that holds the rectifier)
* Using a 40w or higher desoldering tool (or solder braid), remove the black relay (8 contacts, total)
* Replace with the NTE one you bought
Voila! One working amp! Total bench time? One hour. Also, check out the 10000uF 63v caps. If they are bulging or "rattle", replace them, too.
Posted on Jul 26, 2012
Thank you guys so much. You saved my amp!! I've had an Alesis RS150 and have been banging on the case for years because both channels kept shorting out constantly and I didn't want to pay $100+ to get it fixed when I only paid $200 for it. I went out and purchased the PC Relay 12VDC part # 275-0249 from Radio Shack for $5.. Problem solved.. I wonder how many owners of these amps never knew a cheap $5 part turned their amp into junk and it's a shame that Alesis just doesn't care..
Posted on Sep 25, 2011
I am glad that I found this discussion! Although it is not updated recently. I have a 3 year old RA500 with this problem and today I replaced the relay. Now the amp works great again!
I am not an expert but I know how to deal with soldering iron, and I succeded.
Thank you all for your clear instructions and details about this problem. I was able to save a lot of money for the club!
Posted on Jan 12, 2011
I have the RA300 which takes a different relay, harder to find than the smaller one for the RA150. This needs to be 30v 10amp. Don't know much about specs and substituion but knew if I could find the exact replacement I could fix it. Took a couple of weeks and finally AUDIOLAB of Georgia had the finder 44.62.9.012.0000 and their catalog says it replaces the Dong Woo.
They shipped it in two days and I fixed in today, works good, no more cutting out. Yeah! I had this amp for several years and hardly got to enjoy/employ it and was using a Yamaha PA amp in my home studio instead.
It was difficult getting the 8 pins out of the board without burning anything else. Desoldering wicking braid works okay but it would be nice to have a desoldering vacuum. Also, for those ready to try, be sure to label every wire. I almost reversed the white volume and AC leads on reassembly as my labels fell off but I noticed where the ac goes to the on/off switch.
I like Alesis products but you get what you pay for and I just hope that now I will be using it regularly it will hold up. I've never had problems with basic single duty equipment, especially for studio use like this is supposed to be, so if I have to replace it won't be an Alesis.
Posted on Sep 11, 2010
Just letting you know I was experiencing these same symptoms with my RA300. Suspected it was the protection relay... did a search for ra300 relay and found this page.
Went out straight away and picked up a replacement and installed it within an hour. Initial testing is good...
Thanks for this thread - I'm so glad to have this amp working reliably again!
Posted on Jul 15, 2010
I had the same symptoms as others posting here with my Alesis RA-150. After reading solutions here by Cloudio, etc... I replaced the suspected relay and it is working now with no issues. A big thanks to previous posters for their groundwork!
The most difficult part for me was disconnecting the PC board and its connections believe it or not. I am including information I used to fix the problem below as it may be helpful to others:
Faulty relay info:
2 Pole DPDT relay
The rated coil voltage is 12 VDC
Contact Ratings are 5 amps @ 250 VAC/30 VDC
My relay's coil resistance was about 290 Ohms @ room temp.
I replaced it with a relay made by Tyco Electronics. Its specs are located at:
12VDC coil voltage
270 Ohm coil resistance
Contact Rating of 5A @ 240 VAC/24 or 30VDC?
I purchased this relay at a local Radio Shack for $5.50. It is found online at:
This relay has 2 more prongs than the Dong Woo one. There were spots for these on my PC board so I just soldered them in. I cannot attest to this relay's quality, so I am not necessarily recommending this specific relay other than it is easy to find at a local Radio Shack.
Good luck to all and hope this helps someone.
Posted on Dec 29, 2008
It is not difficult to find such a relay. A place you can get it from is this one:
It shouldn't cost more than 4 - 5 euros. I couldn't find thisparticular relay where I live, but - taken an electronic engineer'sadvice - I will replace the old one with a 8A relay which should workperfectly - as he said. 10A are needed on 500W amps and above. Mine isRA - 300W and I never need to work it on max amplitude anyway. I'm about toreplace it next week so I will let you know the results. Cloudio thanx a lot for posting this solution! Let's all hope that this will work! Meanwhile I am about to write negative reviews in several sites about the Alesis amps and their ignorance on our e-mails. I think that everyone of us should...
Posted on Dec 05, 2008
Not a solution as such but maybe a pointer:
I have exactly the same problem first in one channel then in both. I wrote to Alesis - but they were completly unhelpful on the matter and could suggest no solution.
I found that by giging the amp a tap the sound came on. This means the problem is affected mechanically - that sounds to me like a dry solder joint or similar. It might also be a faulty capacitor they can sometimes be affected by tapping.
To date I have not been able to locate the exact point of the problem - I am pissed off with Alesis and wont but another amp from them.
Posted on Sep 17, 2008
I sent this to Alesis today. hope it helps!
I owned a RA300 for about 2 years and am mostly pleased with the performance. However, it recently developed an intermittent problem with both channels cutting in/out (manly the right channel) with crackle here and there. a tap on the case can correct it sometimes.
I noticed after I googled the symptoms other people have the same problem and would like to be pointed in the direction of a solution. I have worked as a technician for a major audio company and understand that liability and policy often keep an employee from offering this kind of information.
with that said, and because it looks to be obvious manufactures defect, I'm asking you to fix my amp beyond the warranty (free of charge) or email me the solution and I'll do it myself. please let me know.
Posted on Nov 24, 2008
I have some Ideas , Two come to mind.Check the OHM load that you are driving it at most amplifiers start having trouble if they are ran at medium volume of higher at less than a two ohm load.This can happen if you are driving two 4 ohm speakers on each channel.If you are running the amp bridged the problem is doubled.
If it is a tube amp or tube preamp in the setup,Try replacing the tubes. They do not last very long if used every day or professionally.
Please wright us back and let us know if this is the problem,If it is not there are only about 100 other things it could be.
Posted on Nov 10, 2007
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