Help replacing a relay.

[imnickb]

I have an alesis rs300 amp that I actually don't hate as much as I probably should. I know virtually nothing about electronics but I know how to solder and I know a little bit about components. The amp has stopped passing audio. When I turn it on, it would usually take a few minutes before it started working. Right before it would pass audio, I always heard a click sound, which I think believe is the sound of a relay switching. Now when I turn on the amp, I never hear this click, and the amp never passes audio. I've looked inside and as far as I can tell, there is only one relay. It says DW321-D12s. I believe it is 12v 10a. Other that that, I really don't know anything. I believe this relay to be the problem. How do I find one? What other information about the relay do I need to know to find one to replace it? I believe if I find the part, I can have a friend install it for me if its beyond my abilities. If this is the wrong place for my post, im very sorry. If you know of a more suitable forum for questions like this, please let me know.

Thanks a lot!

Nick

[Enzo]

We could find a relay like that, but I fear the relay is the symptom, not the problem. The system is not turning the relay on. Usually that means a problem in the circuitry.

The relay protects your speakers. Once the amp powers up and the system decides all is OK, THEN it turns on the relay to enable the speakers. If for example one channel has failed and DC voltage sits on its output, the system detects that and won't fire the relay.

I'd say take the amp to someone for a diagnosis. First thing I would do inside would be to check for a large DC offset in the output of each channel prior to the relay.

[irishsounds]

Hi - There is now an established problem with Alesis studio amps. It is associated with the relay indeed - the contacts seem to be unde-rated.

Here is a link to another forum in which several annoyed Alesis customers discuss the problem: http://www.fixya.com/support/t224708...ut_after_while

[Enzo]

Doesn't sound like the same issue to me. The original post here claims the relay never energizes. That tells me there is probably a circuit failure. The discussion in your link talks about a relay that energizes but has poor contacts so the sound is lost.

SO I see it like a car that starts up but won;t go into gear versus a car that won;t start.

[irishsounds]

Alesis Amp

You could be absolutly right.

Regardless, the relay in question is not of great quality, and IMHO is way under-rated. It would therefore be a useful exercise to replace it. Sometimes relays give problems because of the pulling power of the energising coil.

A seperate secondary problem which seems to be emerging with the Alesis is with the main power capacitors 10,000 mfds 68V - These do not seem to be of good quality and they leak in a lot of cases after just a couple of years use. If anyone is cracking the case, it would be worth replacing these caps.

In the case of the original enquiry, if the smoothing is poor, might it not also lead to switching problem do you think?

[Enzo]

I have a rule of thumb. When something comes into the shop with a problem, we always solve the problem FIRST, THEN we start modifications or upgrades. In my opinion it is unwise to start swapping out a bunch of parts before we know why the circuit doesn;t work. The potential for confusing the issue is too high.

If one of the power rails had completely lost its filtration, the rail voltage would have huge ripple, which would show up on the output bus as a large signal. I don;t know that it would trip the relay protection though, since it doesn;t know where the signal came from, it could be some signal we intended to amplify. It wouldn;t look like a DC offset.

SO that is why my first defense would be to look for DC offset on the output buss before the relay contacts, and as a matter of course, we would always check power supply for proper level and lack of ripple.

And welcome to the forum to both Nick and Irish.

[stingray_65]

just thinking out loud here, but could you check the coil with a DMM to see if there is 12vdc there?

if there is 12 vdc and the relay is not closing, its the relay.

if there is no 12vdc at the coil then something is not sending the control signal to the coil.

[Enzo]

Yes, it is entirely possible the relay drive circuit itself is faulty. I repair that often enough in Samson power amps.

[imnickb]

4 years later and I finally get around to fixing it. I was just going to throw the thing away but thought I'd spend 5 bucks on the relay and give it a go. It was the relay. Get the relay at Radio Shack. They have it in the stores, you'll just have to help them find it. I've never soldered a component in my life but it wasn't hard once I got the old relay off. 12VDC Coil DPDT Miniature PC Relay - RadioShack.com