NAD 214 protection relay

During low volume listening with a mains supply prone to spiking, my NAD 214 amplifier suddenly switched itself off and went into protection mode, i.e. there is now no relay click when the amplifier is switched on so the red light stays on rather than turn green. No sound is produced from the amp at all.

Obviously this is a problem with the speaker prortection circuitary, what do you guys suggest I look for to solve the problem? Is the relay burnt out? Can't see any cracks in the soldering, but as said before, any cracks could be very small.

A previous problem I had with the amplifier was that the nad 214 amp would lose a significant amount of sound level in the left channel, it would sometimes even distort significantly. Both these problems were solved by switching the amp off, then switching back on again. After switching back on, the amp would be fine again.

Any ideas???
 

Netlist

Ex-Moderator
2003-01-18 9:50 am
I don't know that particular amp but both problems could be related to each other. First of all I would suspect bad solderings.
Next would be looking for exhausted caps. Measure the DC value at the outputs. If that's fine, let's say below 50 or so mV, a capacitor in the relay circuit could be the cause.

/Hugo
 

anatech

Administrator
Paid Member
2004-06-06 8:31 pm
Georgetown, On
Of course, the obvious, there is something wrong with the amplifier and the protection circuits are working as they should.

Check with a meter for DC offset on the outputs before the relay. I'm guessing the current trip is not involved as you didn't say anything about smoke or fuses. :D

-Chris
 
Definitely the speaker protection relay. Apparently burn-out of the protection coil in the NAD 214/216 is fairly common.

I now need to find an appropriate replacement for the relay. The current part in the amp is labelled "Type DH2U, 48 VDC, TV-3" Made by DEC?

Anyone got any ideas for an appropriate replacement for this relay?

Cheers!!
Ben
 

violagran

Member
2008-10-28 7:27 pm
Hi Ben,
Pinout and coil voltage are the most important. Adjust the resistance in series with the coil for correct voltage across the coil.

-Chris

It´s a long time since this was posted,sorry. I´ve found a 24vdc relay as a replacement for the 48vdc an Omron Omron G2R-1A-E-DC24 10A (although 10A instead of 5A) that is original in my NAD 216. The resistors that I can see in series with the relay are a 1W 1K5 and a 0.5W 3K9. In the schematic they appear as R388 and R386 respectively. Could you tell me what values I would have to change them to so the voltage was corrected from 48vdc to 24vdc. From alot of your other posts, I´d love to ask you a few questions about my Counterpoint sa5 as well.
 
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Thinkcat

Member
2008-06-09 6:34 pm
It´s a long time since this was posted,sorry. I´ve found a 24vdc relay as a replacement for the 48vdc an Omron Omron G2R-1A-E-DC24 10A (although 10A instead of 5A) that is original in my NAD 216. The resistors that I can see in series with the relay are a 1W 1K5 and a 0.5W 3K9. In the schematic they appear as R388 and R386 respectively.

I recommend you simply go for a 48 VDC relay. Because there is a certain amount of power dissipated in the relay coil, about 0.3 to 0.9 Watts. It means that power per the voltage of the coil. With 60 V rail in the 216, that leaves only 12 V (only 25 % of the coil's rated dissipation) for the resistor. With a 24 VDC relay, you would need to dissipate six times that.

The coil is, in an usual 48 VDC relay, around 4 kOhms. In your Omron, it is 1.1 kOhms and the dissipation is 530 mW. The current is 21.8 mA. You will need a 1 W, preferably 2 W fusible resistor. For some reason, a simple calculation will give 1.1 kOhms for the resistor, but there is a 1.5 kOhm according to the schematic. The same simple calculation would recommend 1.5 kOhm for the resistor with the 24 VDC relay (i.e. you need double the current but you have thrice the voltage over it).

Maybe 1.8 kOhms would do? Recheck these. And remember to upgrade the power rating. Otherwise you will burn out the original R229 immediately. I can't find any 3k9 resistor anywhere in the circuit or the BOM of either 214 or 216.

I can't and won't be held responsible for anything, because I'd simply get a 48 VDC relay (Omron G2R-2-DC48) with 4.1 kOhm coils and keep the original resistor.
 
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