Help with audio problem

darklight00

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I am having some audio problems. I have an old Lexicon DC2 with processor an a Sherbourn 5.1 power amp. I am having some issues and was wondering if someone here could help or have an idea of what it could be. The problems is distorted, scratchy sound that also cuts out. It is an intermittent problem that does not happens all the time. It usually happens in my surround but sometimes in the front and center speakers as well. Its not the speakers or the speakers cables since I tried them with a receiver and did not have any issues. In the audio link below you can hear the problem as it happens. I would like to know if you think is the processor or the amp. Any feedback will be greatly appreciated.
Audio Problem mp3
 
Possibly an electrolytic capacitor, the only thing you might do is open it up and have a look for a bulging or leaking cap. Other than that you’ll need to take it in for repair
 
Naim amps need a service every 10-15 years, after that point their is a risk of one or two caps going off (they iuse some better sounding ones that unfortunately are ‘lifed’ Most caps are good for many years 20+ but as I understand there were some quite poor quality caps in the industry around twenty years ago.

Might even be worth calling Lexicon (Harman ?) and seeing if there is any advice, you might be lucky enough to find a service guy who says, have a look at the two big caps near the power supply and see if the tops look domed, we have had problems with them for example. Then you could find a local service guy to swap them out, or even do it yourself 😳
 
It could be either, probably worth looking at both, you might even find a date stamped on some caps. Which might help at least knowing that have been in place for 20 years. My guess was the processor as it seems to be moving around a little, both power supplies will do all channels though

A lot of older caps will last 40 years or more, with no problems, but sometimes they might be a bit under specced and get hot which causes them to deteriorate much quicker
 
Sounds like poor contacts in the protection relay in the power amp to me. sometimes turning it up louder briefly will make the fault go away temporarily, or a sharp thwack on the top of the amplifier, or just leaving it on for an hour can do the same.
Could even be down to a poor connection somewhere in the P amp or processor or a dry joint or even a selector switch. I would try each ch of the power amp individually with a different source (a smart phone with 3.5 jack to phono lead and playing some music will allow you to adjust volume to test it) If all channels check out on the power amp start looking to the lexicon. BTW it doesn't sound like a capacitor issue to me (repaired loads of amps in the past)
IMPORTANT! Whatever source you use to test the power amp make sure the volume is turned to MINIMUM before you play music or you'll blow your speakers.
 
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@Kapkirk thanks so much for your reply. I checked the amp with cell phone and it is the amp. As soon as I stated playing music I noticed the problem and you were right about the volume also. Sometimes its worse when the volume is lower. So you think it might be the protection relay on the amp? If it is the relay is it something that can be fixed?
 
Great work in detecting the issue is with the power amp.
Well if you hear a click when the amp is first turned on everytime, that is an indicator that the amp has protection relays, not all amp designs have them. It can be repaired but it is not really a job for the average person. There are two ways it can be remedied, the quick cheat way which involves cleaning the contacts inside the relays (pretty tricky as you have to remove the outer case on the relays and replace it without breaking them) this is a short term only solution as the problem comes back after about 20-36 Months, or the proper way which is a major strip down and main PCB out and then to replace the relays -which for an average technician is about a morning's work depending on the complexity the amp.
If you do not hear any clicks at power on it means the amp doesn't use protection relays and could instead be any raft of other issues. For instance the volume pot which can be sorted with a few squirts of contact cleaner (if non digitizer type) or just a dry joint somewhere. Without putting it on the bench and testing it properly it might be a problem for a non technical person to pinpoint.
 
@Kapkirk mine has relays as I always hear the sequential clicks as of each amp when I turn it on. Now my doubt is if anyone here in my country would be able to do this job. Are relays of this type easy to find?
 
Yes the relays are normally pretty easy to obtain unless Sherbourne have used a custom type (unusual) and it shouldn't be a difficult job for a competent engineer. There are still plenty of electronic engineers about who could do this job if you look and do a bit of phoning around, although we have lost quite a few along the years due to the throw away world we now live in.
I am guessing the company have gone out of business now and you are in USA? It really would be a shame to just throw the whole amp away for a relatively simple fix but if it does get much worse you may just have to move on a get a new 5ch amp.
 
Here's a similar problem & repair with a NAD power amp to give you some idea.

 
Here's a similar problem & repair with a NAD power amp to give you some idea.
Thanks so much again... My friend and I opened the amp today and we cleaned the relays. Its working fine thus far but now I lost one channel this coming week will will open it again to try and find out what happened. This is the relay that the amp uses I tried finding the exact one on the web, ebay or amazon but I dint find the exact one. On ebay I found some but there were some differences. The first picture is the relay from my amp the second one is the ones I found on ebay. Do you think those would work? BTW I Iive in the Dominican Republic a small island on the Caribbean not USA
 

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It has a slightly less Current rating at 10A so it would be better if you can get an exact replacement rated at 15 amp 24v. Have you tried RS online or Farnell/CPC?
As long as the pins line up and size is the same that relay should still work ok if you're really stuck.
 
It has a slightly less Current rating at 10A so it would be better if you can get an exact replacement rated at 15 amp 24v. Have you tried RS online or Farnell/CPC?
As long as the pins line up and size is the same that relay should still work ok if you're really stuck.
I could not find the exact one. They are discontinued. I ordered these from Mouser hoping for the best. https://www.mouser.com/ProductDetail...OMshUVEg%3D%3D
 

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