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Do amplifiers go bad???


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#1 of 13 OFFLINE   AntonS

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Posted August 08 2005 - 03:02 AM

I have Sherbourn 5/1500A amp. I bought it about 3 years ago and it's been working very well - until recently.

Not long time ago I started noticing that the sound "breaks up" or becomes uneven. It doesn't break completely, it's even hard to tell from the listening position what exactly is happening except you just feel that the sound is not right and is not full. If you come close to the speaker you'll hear that the volume slightly changes all the time.

Some more facts:
1. It's not the pre/pro. I first noticed it happening with the old receiver, since then I replcaced it with a new one and a different model - it's doing the same thing.
2. It's not the source (CD/DVD). It does the same with calibration tones generated by the receiver.
3. Not the cables - I replaced the interconnects and checked speaker wires - everything is fine.
4. It can do it on all channels (!), but of course its most noticeable in the front.
5. It comes and goes. Sometimes it is very noticeable, sometimes less, sometimes it does not happen at all, sometimes it's the center channel, sometimes one of the fronts, sometimes two of them doing it.
6. It does not depend on the volume.
5. The #4 is very strange as the amplifier has monoblock design - each channel has its own power supply.

The bad thing that although the amp still have warranty and I did buy it from an authorized dealer, I've lost the receipt. I wrote Sherbourn tech support about a month ago - never got an answer (have bad feeling about their tech support already.)

Any idea what could it be? If not the amp, can it be main AC power? (hm... then why the same at low volumes and why it didn't do it before?) Speakers? (all 5 of Paradigm Studio?-don't think so) If the amp, why all channels in a monoblock amp? Some electrolyte capacitors are going bad?

Anyway, any help will be appreciated.

#2 of 13 OFFLINE   Phil A

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Posted August 08 2005 - 03:25 AM

Anton, does this happen when a source is playing (e.g. CD/DVD) or just when the test tones are on?

#3 of 13 OFFLINE   John S

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Posted August 08 2005 - 03:27 AM

Tough one, short of try'n another amp, I'm not sure how to tell you to proceed. AC could cause it, but unlikely, the amp most likely has large caps to make sure it has clean operating power through AC supply side fluctuations.

#4 of 13 OFFLINE   MikeDuke

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Posted August 08 2005 - 03:39 AM

It could be that one or more of the channels are going bad. It seems that you have tested it pretty well. Don't know. My guess would be the amp. Any way to get a temp one for testing? It could be that some of the more delicate electronics on the inside were damaged. But this is all speculation. The first thing I would try is moving speakers around to see if the sound moves with speakers. I hope at least some of this is helpful.
P.S I have a similar problem. All of a sudden my left speaker is playing 10db lower then my right. So for me it may be the speaker, amp, cables, preamp, gremlins. Who knows. But it will be an effort to figure it out.
I know what I like when I hear it

#5 of 13 OFFLINE   AntonS

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Posted August 08 2005 - 03:59 AM

Quote:
does this happen when a source is playing (e.g. CD/DVD) or just when the test tones are on?


Both. It is just more noticeable with test tones (either from Avia or receiver-generated) because of uniform level of pink noise.

Quote:
The first thing I would try is moving speakers around to see if the sound moves with speakers.


I did try doing that - of course the first thing I suspected was bad connections. It was not the case. If I pick a time when it's happening bad on one of the channels and connect a different speaker to it - it started to happen for that speaker.

I also did try another amp - the one in the receiver. Ran it for a while and did not notice anything wrong with it. On the other hand sometimes there is nothing wrong with the sound at all with the Sherbourn either. Then all of a sudden it starts happening again.

What bothers me that the Sherbourn has monoblock design. Every channel has its own power supply, capacitors, etc.

I wonder what kind of effect on the sound bad caps would make. Theoretically bad batch of electrolyte capacitors would start going approximately at the same time.

Anybody had experience with Sherbourn tech support? How good are they? I don't like the fact that they didn't bother to answer e-mail (I've checked that I sent is two months ago). I wonder if they keep track of serial numbers for sold units. Wish I could find the receipt, I would have made it a lot easier, but I looked everywhere...

#6 of 13 OFFLINE   Phil A

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Posted August 08 2005 - 04:05 AM

Anton, for the receipt, did you try going back to the place you bought it for a copy? I've done that once for something that was about a yr. and half old. Did not need service at the time but what I bought had a 5 yr. warranty and I wanted to make sure I filed and kept the 2nd copy.

#7 of 13 OFFLINE   Phil A

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Posted August 08 2005 - 06:13 AM

PS - have you tried both this E-Mail and tel. no?

info@sherbourn.com

978-663-7385 between the hours of 9 a.m. and 5 P.M. EST

#8 of 13 OFFLINE   AntonS

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Posted August 08 2005 - 07:13 AM

I haven't called Sherborn yet. I will. I'm trying to get some info first and make sure I'm not crazy and it is really the amp. I cannot provide sales receipt anyway, and they have pretty scary warranty policy: http://www.sherbourn.com/warranty.php Looks like I'll be 'expressly excluded' from warranties...

Tomorrow I'll try to contact the place where I bought the amp. The place is Sounds Terrific in St. Pete, FL, they are closed on Mondays. I doubt that they keep almost 3-year old information though.

#9 of 13 OFFLINE   Phil A

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Posted August 08 2005 - 08:51 AM

They are required to keep sales records, not only for the IRS but the State of FL. From memory the state of FL has a 3 yr. statute of limitations for sales taxes. They must keep those things longer as it is not uncommon when the state conducts audits for them to secure extensions of the statute of limitations. For business purposes they should keep things at least 7 yrs. but 3 yrs. would be a bare minimum. If they did not have records and the State conducted an audit, the State has the authority to estimate what they think they omitted. Those estimations are never in the taxpayer's favor. They may have things stored off site so it may not be something they can get immediately.

#10 of 13 OFFLINE   Kevin. W

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Posted August 08 2005 - 12:24 PM

In this day an age of computers and if you bought from an authorized dealer, they should have taken your personal info when finalizing the transaction. Everything should be stored on their network. I've been dealing with the same Local dealer for 6yrs and all he has too do is punch in my phone number and he can pull up my purchase history. Now you dealer may charge you for a copy of the receipt.

#11 of 13 OFFLINE   Chu Gai

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Posted August 08 2005 - 12:43 PM

You say you checked your speaker wires. Can you shed some light on how they're terminated at both ends?

#12 of 13 OFFLINE   AntonS

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Posted August 08 2005 - 02:05 PM

I'll check with the dealer tomorrow.

Chu, what do you mean by terminated? You mean connectors? I have fork terminals soldered on both wire ends, and they are just tightened on the amp and speaker connectors. I used a tool to tighten, not just by hand. I think they make pretty good contact. Do you think it may not be enough?

#13 of 13 OFFLINE   Chu Gai

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Posted August 09 2005 - 12:49 PM

I think it's a possibility based on some of the information that you've shared Anton. Why not snip a bit off of each end and see if that makes your problems go away. All you'd be out is a couple of inches and some time.





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