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Old 3rd January 2010, 02:28 AM   #1
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Default Sherbourn, Bad Caps? Newbie needs help

Hello everyone,

I work in the sales and system design end of the A/V industry, but am extremely new to most of the actual repair and workings of two amplifiers I own. I have a 5ch. and a 2ch. Sherbourn amplifier 5/1500A. The chassis are the same and are of a modular card design. Each channel has its own card and transformer. In at least two channels on the five channel and one channel on the two channel I am have the same issues. There is crackling and sometimes the channel won't work at all. From what I am reading, this could potentially be a problem with the caps going bad. Is this the case? The amplifiers are 12-13 years old. I have never done any major repair like this in the past, but am interested in the undertaking. If it is indeed the caps going bad, what should I replace them with? I would like to replace them all at once so the amp continues to work down the road and the channels are matched. I am not sure if the caps may have any bearing on the overall tonality of the amps, but if I could I would warm them up a bit. For my taste, they are too analytical with my Monitor Audio GS60's. What tools and parts would I need and can I do this as a newbie? Any other parts I should replace at the same time? Any other advice would be appreciated.

Best regards

Britton
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Old 5th January 2010, 12:34 AM   #2
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Maybe a list would be easier since no one has responded.

Problems:

  • Channels on two different amps I own are starting to go. Sometimes they just do not work other times they scratch and hiss. These are stand alone amps on different systems both same make model and age.
  • I am new at this, but familiar with things on a conceptual level.
Thoughts:

  • From things I have read these problem could be as a result of the caps going bad.
Goals:

  • Fix amplifiers with new caps on all channels if that is indeed the problem.
  • Warm amplifiers up a bit if that can be done through selection of specific parts.

Please help! Are bad caps my problem?
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Old 5th January 2010, 01:26 AM   #3
poynton is offline poynton  United Kingdom
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If possible, some photos of the modules and how they are inserted may help.

My first thought would be bad contact rather than caps.


Andy


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Old 5th January 2010, 04:03 AM   #4
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Old 5th January 2010, 04:05 AM   #5
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There are a few pics of the amp. I have more posted on my flicker account.
Amp - a set on Flickr
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Old 5th January 2010, 04:06 AM   #6
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I assume by contact you mean that something has come loose somewhere in the chain. Wondering if that could be the case for 3 channels in two different amps.
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Old 5th January 2010, 04:07 AM   #7
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Guys I have moved this to solid state. Troubleshooting is for problems with the forums.
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Old 5th January 2010, 04:11 AM   #8
Stuey is offline Stuey  Australia
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I have no experience with these amps, but are the modular cards mounted in sockets like a PC? If so, maybe they require removal and reseating.

My first thought, however, is that a selector or switch requires cleaning. I can't see from the photos that they have any such selectors, though.

Last edited by Stuey; 5th January 2010 at 04:16 AM.
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Old 5th January 2010, 04:35 AM   #9
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No, there are hard clips with wiring a wiring harness. I have no doubt that contact is being made on these. I have traced all the wiring and everything seems like its in good shape. No switches or selectors on these. They utilize a pre-amp. Is there a part which can go bad which would cause intermittent output and fuzzy or scratching sound on occasion, often times while in the first 30min of listening.
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Old 5th January 2010, 07:11 AM   #10
poynton is offline poynton  United Kingdom
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AS the design is modular, does the fault move when you change the modules over?


Certainly, it sounds like it could be caps if it lsats only 30mins or so after switching on.




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Last edited by poynton; 5th January 2010 at 07:16 AM.
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