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PostPosted: 16 Jul 2018, 03:25 
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Joined: 26 Dec 2016, 03:46
Posts: 194
Location: Bayarea
I know this is an old thread. Do not replace the caps!!!

You have other problem, might not be a bad solder. Too little information to know and should not guess. If you still around, post the schematic and we can take a look and maybe troubleshoot. Do not blind shoot. Do not start changing components. This is a bad way to start.


Regarding to caps, If it still works, you don't see any bulging, leaking, leave it alone. It's not worth your money to change the caps. When I bought my Nakamichi PA-7, I spent $130 changing the caps ( just parts only as I did it myself). It's supposed to be like 30years old, so it's supposed to be time to change. I looked at the sawtooth wave on the rail and took a picture. I changed the caps, waveform looked exactly the same, there is NO improvement on the sound. It's a total waste of money.

If it is not broken, don't fix it. Your problem is NOT the filter cap.


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PostPosted: 22 Jul 2018, 01:12 
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Joined: 23 Feb 2017, 02:02
Posts: 519
Yungman wrote:
I know this is an old thread. Do not replace the caps!!!

You have other problem, might not be a bad solder. Too little information to know and should not guess. If you still around, post the schematic and we can take a look and maybe troubleshoot. Do not blind shoot. Do not start changing components. This is a bad way to start.


Regarding to caps, If it still works, you don't see any bulging, leaking, leave it alone. It's not worth your money to change the caps. When I bought my Nakamichi PA-7, I spent $130 changing the caps ( just parts only as I did it myself). It's supposed to be like 30years old, so it's supposed to be time to change. I looked at the sawtooth wave on the rail and took a picture. I changed the caps, waveform looked exactly the same, there is NO improvement on the sound. It's a total waste of money.

If it is not broken, don't fix it. Your problem is NOT the filter cap.

Yup agreeded, from my exprence caps usually don't break down


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PostPosted: 12 Dec 2018, 21:21 
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Joined: 26 Feb 2018, 13:59
Posts: 18
Hi Yungman, thanks for the reply to this old thread. I had decided to just upgrade my receiver but am now considering the amp again as much of the cost of the higher end receivers come down to amp power and none of them can touch the Sherbourne.

However, I am unsure of how to post the schematics of the amp as this is over my head. I have a lot of pictures that might help? I had concentrated on the caps as others who have owned this amp seem to believe it's not an isolated incident (and recapping worked for them). When I pulled apart the amp, the caps didn't look bad (no bulging) and the solder joints looked ok to my untrained eye. I will keep an eye on this thread in case any advice comes through. As always, I very much appreciate the time and information forum members offer.

Thanks!


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PostPosted: 13 Dec 2018, 03:39 
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Joined: 26 Dec 2016, 03:46
Posts: 194
Location: Bayarea
Schematic is the circuit diagram. I cannot find it on the web. I did see it's a 5 individual channel monoblock. Question to you is you said static and fading. Is it on one particular channel?

Before you do anything, a few pictures might help.

If it is on one particular channel, with the top of the amp off, push the heatsink module of the one that has problem, wiggle it a little while listening to see whether you hear any noise. This is to check whether you have any loose wire. Then do the same thing to the power supply to see you hear anything fading and noise. What you described, you might have loose connection.

If you can't hear anything doing that, get a wood stick, go in and push the wires inside to see whether you can make the noise, particular on connectors. Do that first and we talk more.


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PostPosted: 13 Dec 2018, 12:41 
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Joined: 26 Feb 2018, 13:59
Posts: 18
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Here are some pictures, at least to get an idea on what I'm dealing with.

I've tried to hook up only three out of 5 channels and eventually I get static/loss of audio in a speaker. I change that speaker to another channel on the amp and sooner or later another speaker has the same issue. So, it does not seem isolated to only 1 or 2 monoblock channels. I've actually had it all work for a day or so with no issue and then it pops up. It's not an immediate problem when the system fires up. Please let me know if any additional images would help. As always, thanks!


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PostPosted: 13 Dec 2018, 22:59 
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Joined: 26 Dec 2016, 03:46
Posts: 194
Location: Bayarea
Jiggle the connectors while you are listening to see whether you can make it fail.

I am pretty sure it's not the capacitor. I read the description of the amp, it is a COMPLETE 5 individual monoblock each with it's own power supply. You don't have cap failure on all 5 channels exactly the same symptom. If all channels do the same thing. Look at the connections from the power cord to each individual power supply to see whether you have a lose connection.

Do you see the indicator light flicker when that happens?

If all else fails, you sure your speaker cable and speaker is good? Remember, it happens on ALL 5 channels. There is NO CHANCE all 5 channels have the same exact problem. It got to be a problem on the common connection:

1) the power cord input through the power switch, surge suppressor, and distribution.

2) From the banana connector through the cable to the speaker.

3) The speaker.


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PostPosted: 14 Dec 2018, 12:47 
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Joined: 26 Feb 2018, 13:59
Posts: 18
It is so inconsistent and random it's hard to nail down and verify that it's all 5 channels. I will run some tests today using the amp and an older receiver with other speakers. Perhaps I can verify a bit more exactly what the problem channel(s) are. I will also follow your advice above and get you more information.

Much appreciated.


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PostPosted: 14 Dec 2018, 13:38 
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Joined: 26 Feb 2018, 13:59
Posts: 18
It may be the speaker terminals..

I have it hooked up and it seems some of the static/crackle sounds change when I wiggle the terminals on the back of the amp. Perhaps the solder is bad inside the amp were they are connected? I will keep checking it over.

Thanks!


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PostPosted: 14 Dec 2018, 16:19 
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Joined: 26 Dec 2016, 03:46
Posts: 194
Location: Bayarea
I cannot imagine all 5 terminals are bad, check the connector of your speaker cable that connect to the amp. You have another speaker cable you can use? Is the problem on the same speaker?


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PostPosted: 15 Dec 2018, 20:00 
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Joined: 26 Feb 2018, 13:59
Posts: 18
For this test, I used some speaker cable that was laying around. It's not terminated, just bare wire ends that I inserted into the amp and speaker terminals and then screwed down. I encountered the same issue as compared to when the amp was hooked up the proper way with good quality connectors etc. I ensured that no bare speaker wire was touching the amp or speaker body etc.

I tested several of the amp channels and at least 3 of the 4 on the amp seemed to have this problem. One of them sounded great with no static or audio drop outs. I will verify but there may be 2 channels that are OK. So, I don't think all 5 need addressed.

I performed the test with a pair of high quality outdoor speakers which have never exhibited any problems. Regardless, the issue I experienced in this test mimics what I have seen in the home theater room with different speakers/cables/interconnects and power cables.


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