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Old 8th September 2010, 08:40 PM   #1
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Default NAD 2140 Power amp problem

Well hello all
Been lurking on here for a while and finally bought myself a stereo after many years of being without one

Nad 6220 Tape deck
Nad 4130 Tuner
Nad 1020 Pre Amp
Nad 2140 Power amp
Mission PCM 4000 Cd Player
Infinity infinitesimal micro speaker system
Infinity infinitesimal Subwoofer

Got all the above on ebay for sum of 134 in total so i was happy as a pig in you know what..... till it arrived and i wired it all up.
The 2140 Power amp wont stay on its like there is an auto protect feature killing power, though i did turn the volume right down and played a tape and if i hold the power button in i get sound no problems.
It literally comes on for a micro second when pressing the power button and instantly clicks off unless you hold the button in

There is no red led power light but the SLC led lights up then fades because the power is auto switching off

I am sorry for my first post to be a cry for help only hours after receiving my stereo and i hope someone here has an idea what stupidly simple problem this might be.
Spoke to previous owner on Phone and he is the owner from new and has never had a problem with the system and even said this is the first time its ever been unhooked (so he could wrap and pack and post) since the day he bought it and set it all up

So here's hoping someone can help me in my time of need all i want to do is play with my new toy
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Old 8th September 2010, 08:52 PM   #2
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If needed i'm pretty sure i have a scan of the 2140 service manual yet to be assembled into a pdf.

dave
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Old 8th September 2010, 09:26 PM   #3
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Thanks for a quick reply Planet10 i'm hoping someone will come along that has an idea what the problem is without using the manual as i am no electronics guy though i am considering learning the ways of you modders once i get this problem sorted.
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Old 8th September 2010, 10:47 PM   #4
Bill_P is offline Bill_P  United States
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The power switch is just a switch, not a circuit breaker. If you hold the switch in and the amp operates normally, then it is probably just a bad switch. NAD protection circuits often disconnect the speakers using a relay but do not turn off the power to the unit. It doesn't seem that the protection circuit is engaging in your amplifier.
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Old 8th September 2010, 10:58 PM   #5
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Thanks for the reply Bill

That makes sense actually after reading up a bit more on protection in amps.
Now to open it up i suppose and bypass the switch to test this

Anyone got a source for new nad power switches?
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Old 9th September 2010, 11:36 AM   #6
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Well guys opened amp up and i honestly dont have a clue what to do to bypass the switch safely
It seems that it is simply a case of the switch not locking in place when depressed
Anyone here can explain to me using the following pics what i have to do to bypass the switch please?

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
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Old 9th September 2010, 12:15 PM   #7
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seems i posted pics wrongly so here is a list of links to full size images


[img=http://a.imageshack.us/img824/3931/1002054z.th.jpg]
[img=http://a.imageshack.us/img841/362/1002056d.th.jpg]
[img=http://a.imageshack.us/img243/5986/1002057.th.jpg]
[img=http://a.imageshack.us/img442/9237/1002059a.th.jpg]
[img=http://a.imageshack.us/img442/6843/1002058n.th.jpg]
[img=http://a.imageshack.us/img375/2582/1002053v.th.jpg]
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Old 9th September 2010, 12:15 PM   #8
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There's something wrong with the thumbnail feature in this forum so we can't see the full-size pics - can you link to the full-size pictures?

If the switch is the type that i know of, it can be repaired and you won't need to bypass it. Check for a locking tab on one side of the switch, if there is one, you simply need to lift it, bend it downwards a bit, and that's all. Also you can try switching it in rapid fashion - it will eventually lock. Then just leave it turned on.
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Old 10th September 2010, 09:03 AM   #9
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Found a local guy who will bypass the switch safely for me
Ill pm you for service book Planet10
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Old 19th November 2010, 05:17 PM   #10
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I need the same kind of power switch (double switch) one half for mains switch (active = Power ON, passive = Power-Off) and one half for switch off the connection between R516 (390R) and neg pole of C520, 47uF (active = off, passive = on).
In the NAD model 3130 this "ON" function after performed "switch-off" serves to avoid buzzing-, bump and noise effects through switch off the mute jFETs Q303/304 (J111) for suppession the preamplifier output signal at the pre-out female plugs so as the power amp input.

Where I can order such kind of doubleswitch - the NAD order code (mentioned in the service manual) are follow:
L432Y034H01 and L432Y035H01
Attached Files
File Type: pdf NAD power switch downscale.pdf (25.8 KB, 18 views)
File Type: pdf NAD power switch top view downscale.pdf (13.5 KB, 12 views)

Last edited by tiefbassuebertr; 19th November 2010 at 05:20 PM.
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