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Old 19th August 2009, 06:41 AM   #1
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Default Help with a noisy NAD 216

Hello all, i have a problem with an amplifier and hope someone can help me with some advise.

http://dymas.ii.uam.es/~jga/nad216thx/DSC02678.JPG

The amp has two problems. First when you turn it on the relay didnt clicks and the protection led keeps on. Ok, i know most nads amplifiers fail that way. So i removed it and bought new one, i also soldered a socket in its place, thinking about buying some better relay or whatever.
With the new relay it does the same. The relay didnt moves. I've checked its pins and it has 48 volts as it should have.

http://dymas.ii.uam.es/~jga/nad216thx/DSC02688.JPG

The second problem if i remove the relay and bridge the other pins, the ones that go to the speaker output. The protection led goes out, and both channels sound. Very bad, but they sound.

I started looking at the board and seen that there is a zone where it is dirtyer than the rest (the picture isnt very good, but you can get an idea)
http://dymas.ii.uam.es/~jga/nad216thx/DSC02681.JPG
also dirty underside the same place:
http://dymas.ii.uam.es/~jga/nad216thx/DSC02694.JPG

Other typical failures i've read are poor soldering and bad capacitors.
I have made another couple of photos to show general soldering. they didnt look the best solders but i cant see why they couldnt work.
http://dymas.ii.uam.es/~jga/nad216thx/DSC02691.JPG
http://dymas.ii.uam.es/~jga/nad216thx/DSC02692.JPG
http://dymas.ii.uam.es/~jga/nad216thx/DSC02696.JPG

So i returning to the dirty zone, maybe one or more capacitors have failed?
I didnt have enough knowledge about electronics, neither equipment. But i started measuring the resistance of some of the capacitors to see if any show a bit of continuity (heard it could represent a failure). I also know that the way to measure was desoldering each cap, but a bit avoiding that, i have found that some simetrically placed caps on the circuit, one of them shows a resistance and the other looks absolutly isolated. I know this isnt much professional but its what i have.

I have left the service manual of this unit in the same directory as the above pictures, so anyone could understand better what i'm saying and give some advise.

At this time i ask. Could some capacitors be failing? i'll be advisable that i renew some of them, maybe all? but, the caps on the power supply board or also the left/right channel ones?
Also i want to ask if i can put in better ones, maybe other kind or bigger ones.
Can some failing caps make the relay not to switch?

Sorry for this brick coupled with my bad english.
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Old 20th August 2009, 04:51 PM   #2
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=================================================
The amp has two problems. First when you turn it on the relay didnt clicks and the protection led keeps on
=================================================
If the speakers not connected to the power amplifier, the follow two reason are there in most cases:

1) DC voltage at the output from power output stage (you must check between switch contacts of relais and amplifier output) If there are DC voltage more as 50mV, you must start your troubleshooting by power amplifier stage of the regarded channel

2) If DC voltage <50mV, the protection circuit works not in the right way. Consequently you must start your troubleshooting there

==================================================
I started looking at the board and seen that there is a zone where it is dirtyer than the rest
================================================== =

Would be dirty zones should be clean, But I am sure, you mean darker instead "dirtyer". There are "Hot Spots" (burned areas), created by thermal overload of certain zeners and resistors. All devices in this aera you must careful checking. Additional you must find out the reason for this; perhaps you must reintroduce small heat sinks by certain devices.

If you post the circuit detail of the devices from hot spot aeras, I can give you additional advices.
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Old 16th September 2009, 07:26 AM   #3
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Sorry for the delay, but i've been on holidays.

As said before i've left the service manual on:
http://dymas.ii.uam.es/~jga/nad216thx/
so anyone willing to help could have it.

Thank you, tiefbassuebertr, i've checked the voltage on the relay out and its near 17v, but as i didnt know surely where to measure i attach a picture of where i checked and voltage:
http://dymas.ii.uam.es/~jga/nad216thx/nad-216-sch.jpg

No, i mean dirty, not re-hotted or burned. I'm sayin theres a "yellower" zone up and down the board. This is in the power supply near the small capacitors. I've changed nearly all capacitors in the power supply and the problem still's the same.

What you recomend the next? replacing transistors? i have not replaced the bigger cappacitors as they looked newer than the rest, and my electronics store doesnt have them.

Thank you very much.
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Old 16th September 2009, 11:32 AM   #4
burbeck is offline burbeck  United Kingdom
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hi there
i have had 2 of these amps with similar fault turned out it was the servo ic on both faulty IC201
good luck
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bob

Last edited by burbeck; 16th September 2009 at 11:37 AM.
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Old 16th September 2009, 11:54 AM   #5
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Quote:
Originally Posted by burbeck View Post
hi there
i have had 2 of these amps with similar fault turned out it was the servo ic on both faulty IC201
good luck
Thank you.

I will try to replace it tomorrow.
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Old 16th September 2009, 12:41 PM   #6
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Hi!

I have a NAD 319 (216+pre) with the same problem that you describe, won`t come out of protection.. I have also got some darker/burnt looking areas in the PSU, I have changed the 4 220uf caps (C210-213), one of them had failed. Also changed C214/C215. No change... :-(

I`ll be replacing Q201 and Q204 tomorrow, as it looks a bit burnt around those too. One of them runs at 10Celsius higher temperature than the other one at idle(measured with laser on heatsink), is this normal, or an indication that it might be broken? Anyone?

I am not getting 1,3V at pin8 on IC202 either(to pull the relay), so I`ll try replacing the diode D211, and C226, as these have a tendency to blow on these amps. ref; click me

@burbeck; how can I tell if my IC201 is broken? Did the ones that were broken look broken, or did you measure it? if so, how? I guess no output on pin 1?

Cheers

- Bjørn

edit: after reviewing the schematics, protection circuit is not exactly the same for 216/319; so I`ll post the one for 319. :-)
Attached Files
File Type: pdf NAD 319 PSU.pdf (43.4 KB, 73 views)

Last edited by Brillegeit; 16th September 2009 at 01:06 PM.
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Old 17th September 2009, 07:36 AM   #7
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Got the IC201 and by the way IC202, D211 (as said in the post Brillegeit links. C226 already changed before) and also the four transistors in the PSU.

I'll replace all of them this afternoon and inform.
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Old 17th September 2009, 11:09 AM   #8
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I can`t replace mine today, I`m waiting for mica-spacers for the transistors. 3 weeks I`ve been waiting now, think I`ll have to change supplier...

@krestudon; please post results here, hope this fixes it for you! :-)

Regards

- Bjørn
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Old 17th September 2009, 11:59 AM   #9
burbeck is offline burbeck  United Kingdom
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hi Bjorn,
just replace it they are very cheap.
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bob
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Old 17th September 2009, 04:37 PM   #10
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Bad news.

Replaced D211, D212, IC201, IC202, Q201, Q202, Q203, Q204 and everything's the same.

Both ICs with a socket, tried new and old but no change.

Any advise?
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