NAD T734 accident

[bubbakittee]

Hi,

I'm new here, so I hope I'm posting in the right place.

I just moved to China, and accidentally plugged my US-bought NAD T734 receiver into a Chinese (240V) outlet. I didn't notice it for a few minutes, until there was a small but sickening explosion. Not paying attention. Not enough sleep, lately.

The receiver is completely dead. I opened it up, hoping that a fuse had blown, but the fuses look OK, to me. On a smallish circuit board connected to the power input, it looks like one of the copper traces is completely melted off the board. I can't see any other obvious damage.

A few questions:
(1) Would you (the experts) expect the damage to be extensive and major, or only localized to a few components ?
(2) Any suggestions on what to check next (though I don't have much in the way of either equipment or expertise).
(3) Any suggestions about repair services ? NAD equipment is apparently made in China, but not sold here, so I can't find a dealer.
(4) If all else fails, anyone want to buy a crispy T734 ?


thanks

bk

[pacificblue]

Originally posted by bubbakittee
(1) Would you (the experts) expect the damage to be extensive and major, or only localized to a few components ?

Try to post some photos for damage assessment.

Originally posted by bubbakittee
(2) Any suggestions on what to check next (though I don't have much in the way of either equipment or expertise).

Without expertise, you may better leave that to somebody else. The least you need is a multimeter to measure voltage and resistance. Then soldering equipment and a source for the spare parts. Does the NAD have a switch for different supply voltages? Usually at the back near the power input. If it doesn't you may as well wait until you return to the US (if you return that is), because it won't serve in China without an additional transformer. For the same money you might be able to get a new amp there.

Originally posted by bubbakittee [
(3) Any suggestions about repair services ? NAD equipment is apparently made in China, but not sold here, so I can't find a dealer.

Any electronics repair service should be able to help you there. If you are lucky, they even charge you less than for a new amplifier. Chinese are tough businessmen, especially when dealing with strangers.

[gfiandy]

Hi, Labour tends to be very cheap in china and the techs out there are very resourcefull; you can probably find someone who will fix it for very little money if it can be fixed.

The likely problems will be overvoltage on the input parts to the voltage regulators so the smoothing caps may be damaged and the regulators may be damaged. The other problem is you will have put twice the normal voltage on the amplifier rails and this may have damaged some of the transistors and possibly the bulk storage capacitors in the amplifer although if you didn't play music through it they may have survived as there would have been little current flowing through them. Basically you can cause a lot of damage by doubling the input voltage to an amplifer but sometimes you get lucky and much more than you expect can survive.

Andrew

[bubbakittee]

Thanks for the comments, everyone.

Actually, I just noticed that I wrote the wrong NAD model number.
It's a T742, not a T734. Probably doesn't affect anything, though.

The amp does not have a voltage input switch. This is surprising, since essentially the same amp is sold in the UK (240v) and the US (110v).

I have a multimeter, and have tried measuring the resistance of a few components on the damaged circuit board. The ones I tried all had infinite resistance (according to my meter). Not a good sign, I suppose. I'm actually not sure what these components are, though.

I will try to find a good service guy, as you folks suggested. But, experience says I should have some idea how to fix the problem myself before negotiating a price with someone else. Especially in China.

I didn't play any music through the amp, so maybe the damage is not too extensive. I will post some pictures, but I'd be surprised if they tell you much.

I won't be returning to the US for two years, and I can't live without music for that length of time. If the service idea doesn't work out, I guess I have to go shopping. There's not much good gear, here, though, and it's all ugly silver/gold colored stuff. I like black. Yes, I know it's dumb buying criterion, but, as you can see from the original post, dumb is my specialty !!

[pacificblue]

Originally posted by bubbakittee
There's not much good gear, here, though, and it's all ugly silver/gold colored stuff.

That only seems so at first glance. If you are in Shanghai, you are in one of the few places in the world, where you can get virtually everything. It helps of course to know some local people that show you the right places and make the right contacts.

And then there is still HongKong, from where they can send you all the stuff you need per web order.