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Dilemma

362 Views 6 Replies 3 Participants Last post by Howaryuh, Dec 30, 2005

Howaryuh

Discussion Starter · Dec 23, 2005

The dilemma: Put in a new floor and to save time moved the cabinet with all components inside, very little if any jarring or bumping. After floor installed, unit moved back into position and a few re-connections made. Left rear channel has dropped out of the amp, a NAD T762. I could take it to the shop, but with timing being everything, we are having a new year's eve party and I highly doubt getting it back in time. I'm thinking perhaps a loose connection was compromised during the move. I guess worse case I just use the front channels, but...... and I did do a myriad of tests, eliminating speaker itself or the speaker wire as the cause, and have reconnected to the amp a few times. Any suggestions for a quick fix on this? Perhaps opening the unit up and having a look (not that I would know what to look for). Any input appreciated.

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John151

· #2 · Dec 23, 2005

You can run some tests to try to narrow down there the problem is. On the back left side (left when looking at the back), there is a bunch of jumpers aligned vertically. These are the pre-amp ins and outs. The jumpers simply connect the Pre Outs from th electronics to the Pre Ins for the amps.

If you remove the jumpers for the 2 sourround channels, and then use stereo IC cables to connect them back, but swap the left and right, you will find if the problem up stream from the amp, or down stream from the amp, or the amp itself. If the problem transfers to the other speaker, then the problem is up stream of the amps. If the same speaker is still out, then the problem is either the amp, or down stream from the amp. If the problem appears to be the amp, or downstream from the amp, you can also swap the jumpers with the bad channel with a front channel, and see what happens.

Note that if it is the amp that is bad, you have 7 amps total, and if you are only using 5, you can use ICs to send the left rear signal to a different amp, such as one of the back surrounds (and then change the speaker wires to the corresponding terminals).

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Howaryuh

Discussion Starter · #3 · Dec 24, 2005

Thank you for the suggestions John. When I swapped the jumper connections between left and right, the problem did indeed move to the other speaker. I guess this is good news in the long term (?), but not so for the short term. Do you think it's worth looking inside unit to see if a card or wire was jiggled loose? Your reply was indeed appreciated.

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John151

· #4 · Dec 24, 2005

Well, we now know the amp is fine, along with the speaker, and speaker wire, so the problem is either inside the 762, or possibly in the source. How is the source connected? Also, can you test this out with more than one source?

I have no idea of what to expect inside the 762. It is out of warranty, so you have no concerns about voiding the warranty by opening it up. I am trying to make an educated guess of what would be indside, and I am wondering if the input is digital (Coax or optical), would there be any connections inside? My best guess is the only connection would be to the Pre-Amp out. Everything else would be circuit board, and I would not exepct any bad connections to be visible, or servicable, by a lay person.

Three caveats:

1) I am not an EE or technician, so take my advice with a grain of salt.

2) Be careful if you open up the T762. There are probably several capactitors that can store a healthy charge, which could deliver quite a shock.

3) When (if) you open it up, be careful not to discharge any static from your body to the internal components. Don't wear nylon socks, and touch the chasis frequently (and before touching anything inside).

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Thomas Willard

· #5 · Dec 25, 2005

If you swapped the connections as you indicated, then that would indicate the speaker and wires are OK, but the amp is not OK. Sounds unusual that just moving the equipment would cause a channel in the amp to cut out. I suspect it is something simple.

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John151

· #6 · Dec 25, 2005

Quote:

Originally Posted by Thomas Willard
If you swapped the connections as you indicated, then that would indicate the speaker and wires are OK, but the amp is not OK.

When he swapped the INPUT into the amps, the problem switched sides, which indicates that the problem is upstream from the amps.

Quote:

Originally Posted by Thomas Willard
Sounds unusual that just moving the equipment would cause a channel in the amp to cut out. I suspect it is something simple.

Agreed, but the problem may have been there before the move and was only noticed after the move. Also, it is possible that unplugging, and plugging back in, could have caused a problem, such as a power surge, or even a static shock could have zapped a circuit.

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Howaryuh

Discussion Starter · #7 · Dec 30, 2005

Thank you for the input John and Thomas. I have two separate sources hooked up right now, both digital coax (cable box) and optical (DVD). Problem exists with both. This unit has not been the most reliable since day one, and has had a major overhaul (thankfully while under warranty). I'm thinking to hookup the speakers to Zone B outputs to get them in service for the time being. I am convinced opening the unit up myself will do no good and will take the unit in to the repair shop in the new year. Thanks again for the thoughts, best wishes for a happy new year!

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