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Old 18th April 2014, 12:49 PM   #1
dman535 is offline dman535  United States
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Default NAD 1300 - Problem with static

I have an NAD 1300 that was working great. All of sudden it sounds like and FM tuner with a crappy antenna. There is this light static on all the inputs, including the phone. I checked with headphones and the sound is present. Any thoughts on where to start looking?
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Old 19th April 2014, 03:08 AM   #2
Bare is offline Bare  Canada
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Location: vancouver
Surely someone will be along shortly to offer assistance.
Not me tho :-)
NAD's die .. regularly.
Decent (while they last) sound.. pathetic build quality.
Fix one corner and the opposite corner subsequently fails.
Waste of time/energy/ and hopes imo.
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Old 19th April 2014, 04:24 AM   #3
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There is a free download schematic here.
There are not enough clues in your description to suggest where to be begin looking, not even if the noise is equal in both channels but there are a number of opamp circuit sections with switching that will provide a similar number of logical ways to eliminate most of the circuits in the preamp. as the possible culprit or noise source.

There won't be a magic single answer here - you need to find the area of the fault by a simple divide-and-conquer method, then determine what you are left with. If you cannot get further than eliminating only say, the phono section, you may have to physically disconnect the main tone control/section from the output stage and so forth to isolate the problem. This isn't rocket science but neither is a simple prod with a magic wand that maybe you hoped someone would suggest.

You have to follow the schematic logically to identify the signal path in each section and isolate it to check its effect on the noise. That may be a long process, depending on your experience with line-level signal tracing.

If you still find the noise present even when all the processing circuits are disconnected by switching out, bypassing and otherwise disconnecting, I'd be looking at the power supply itself and then the JFET muting circuits in output amplifiers as a possible source - simply because they are a known problem. If the fault is common to all inputs in both channels, just think - what is in common with both channels? Odds are it's going to be the power supply.

Otherwise, it may not be simple at all and you may need to look at what instruments you have, as something like a small powered speaker and signal or tone generator to check what circuits are active when you start disconnecting. A 'scope, of course, makes a great visual aid for distinguishing fault locations from the general areas affected - with a little experience.
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Old 19th April 2014, 02:20 PM   #4
dman535 is offline dman535  United States
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My post was probably a bit premature, this morning I ripped the preamp out and dug into it a bit more. A mounted Opamp in my DA convertor was loosed causing some weird power feedback loop through the preamp. It was odd that the noise was coming through all sources, not just the input from the DA convertor. I am sure at one time I will have to dig into the 1300 to fix something. Thanks to all for the replies.
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