Need verification on a NAD 310 Integrated Amp

J

JensenMan

New Member
Hi everyone,
I just picked up a NAD 310 Integrated Amp on Ebay yesterday. I removed the cover and blew out the dust and debris from the previous owner (which there was alot) and noticed that, where the the transistors (?) mount to the heat sinks, there seems to be some smearing of thermal grease on the heat sinks. Like finger prints and smudges. To me it looks like a quality issue from the factory or someone has been inside this unit for a repair. The screw heads around the board do not look like they have been removed. Nothing looks to be chewed up or anything. If you have a NAD 310 and it is not too much trouble, can you post a hi res picture of how your heat sinks look and if they are free of grease smudges? I am interested to see if I have a molested unit or not.

Thanks,
Dave

Oh yeah, I paid 145.00 total for it. (laugh if you want)
 
I'm not sure if this helps, but I have a 3130 (and judging by the dust inside and screw heads, it's been unopened) and it too has a few smudges of thermal goop on the heatsink. Not a huge amount, but the odd stray strand is marked with a fingerprint.
 
I no longer have this unit, but hopefully these may help:

NAD3101.jpg


NAD3102.jpg


NAD3103.jpg
 
JensenMan said:
Hi everyone,
I just picked up a NAD 310 Integrated Amp on Ebay yesterday. I removed the cover and blew out the dust and debris from the previous owner (which there was alot) and noticed that, where the the transistors (?) mount to the heat sinks, there seems to be some smearing of thermal grease on the heat sinks. Like finger prints and smudges. To me it looks like a quality issue from the factory or someone has been inside this unit for a repair. The screw heads around the board do not look like they have been removed. Nothing looks to be chewed up or anything. If you have a NAD 310 and it is not too much trouble, can you post a hi res picture of how your heat sinks look and if they are free of grease smudges? I am interested to see if I have a molested unit or not.

Thanks,
Dave

Oh yeah, I paid 145.00 total for it. (laugh if you want)
Click to expand...

Dave,

I could send hi-res photos of the inside of mine, but I've repaired and modded mine, so it won't look factory either.

But, if you can post/send me a photo of the inside of yours, I may be able to help you out.

One hint though: If you don't see a BUK555 power MOSFET on each side, it's been repaired.
 
Lets see if I can do this. Here is 3 pics of the unit. I see finger prints on the bottom of the circuit board and the grease is really sloppy. Don, thanks, I do have both of those MOSFETs. Check it out.
P1000383.jpg


P1000382.jpg


P1000381.jpg
 
Back in the early 90's (a couple of years before this model) NAD units, specifically the 7225, 7240, 7240pe series, would come out of the box with transistor issues. Once the techs fixed it and calibrated the bias, they worked great for, well, I guess forever.
These don't look like a factory job. This is a sloppy tech or wanna-be.
Does it work right?
 
Thanks, it seemed to. I started to get a little crackle out of the left channel, though. Also, when the power button is turned off, the green power light stays on and fades slowly. If the CD player is playing, it slowly fades before it shuts off. Is this normal?
 
I'm sure this unit has NOT been repaired. I don't even think the transistors have been out of the unit at all, the leads are too straight, the bodies are on the heatsink too straight also.

If you look at the driver transistor, A1306 and the bias transistor, C3421, they haven't been touched at all, the mess around them is smearing from the grease on the power transistors.

The soldering on all the transistors is too neat to have been repaired. No, I don't have x-ray vision. BUT, if those transistors had been taken out, the amp would have been upside down, or on its side, heatsink down. This would've left a nasty mess of both old and new rosin from desoldering and resoldering. There's not a trace of anything other than the rosin that would normally be there from the factory.

A repair job that still had those unobtainable BUK555 power MOSFETs would be a rare sight indeed! Also, there are no signs on the board that any of the power transistors died from overheating, the board is pristine around them.

My theory? One, whoever built that amp got happy with the heatsink grease that day, and didn't clean up. Or two, some owner got concerned when the heat over the years dried the original heatsink grease into a caked-up mess, and unbolted the power transistors, folded them down a bit, and swabbed on a liberal amount of heatsink grease, and remounted them. The second is most likely, and was actually a wise move, but sloppy execution.

For those not familiar with the little gem that is the NAD 310, the entire power amp section would fit on the back of an envelope even easier than the Gettysburg Address. Both channels. The amp is about 30Wpc, but it can kick out a LOT of current. The circuit is very simple, and clean, but almost all the output power goes through the BUK555. Scroll back up and compare that one to the others in the pics. It sounds great, but that's a lot of heat on one little spot. If the amps aren't in a well-ventilated spot, they will eventually cook that MOSFET, which is the most common failure on these.

Dave,
Find something like hockey pucks, or blocks, anything really to put under the feet of the amp, the stock feet don't quite do the job of letting enough air get to the bottom. If the amp doesn't get its own shelf, put blocks between it and the next component also. Just make sure the amp gets AIR.

Also, while the circuit is a brilliant design, the bean-counters at NAD saddled it with those "lovely" Wendell caps rated at 85º C. Unless the amp is well-ventilated, it really needs 105º C temp caps near the heatsink.

Why mention the caps? Well, the area around the left channel of the amp gets hotter than the right just because of location inside the chassis, and those caps will dry out quicker. So, when it gets close to recap time, you will start hearing crackles in the left channel.

Here's a pic of how I have mine set up, on top of two defunct Bang & Olufsen speaker cabinets (couldn't bear to throw away all that rosewood), and a set of "high-end-audiophile-approved":D blocks separating all the components. And yes, I use one or the other of those two preamps in the photo with my 310 (told you it was modded). In fact, none of the components in the photo are exactly as they seem . . .
 

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I am getting one of these soon with a dead channel. After reading this thread I suspect a dead BUK555 mosFET. Will see though. I used a 310 about 10 years ago when I started with the whole hi-fi game - very nice amp!
 
NAD 310 Intergrated amp

I have the same amp ! Are those the bias pots, and if so does anyone know what it should be set at?

Thanks !


I just picked one up for $75.00
 
NAD 310 Intergrated amp

Hi there I just picked one of these up! Are those the bias ,and if they are does anyone know what they should be st at?


Thanks !


MR
 
I didn't know that NAD's have toroidal transformers - do all of them do?

Just curious...
 
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