NAD 2200 In Protection Mode

theoman

Confused Member
Subscriber
I picked this up today with the matching preamp, when I got home I plugged the amp in and it was in protection mode. I blew out all the dust with air and then hooked it up.
the unit played for awhile then the right channel went out then in protection mode. it did sound a little muddy but it may have been my grade advents.
Is there a common problem with them. I did see people replacing the 4 large caps on them.
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IMG_9163.jpg so far no capacitors bulging or leaking? no burnt smell? I'm going to start with speaker protection relays whats the best way to clean oxidized relays? just contact cleaner?

Do the tops of the relays snap off?
 
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Those look like the original relays, and yes, the tops open. If gunked up, cleaning will buy a little time, but ultimately you will need to replace. There is a recent thread where replacement with near exact fit is discussed. I have heard that paper between the contacts of the relay works, when doused with Deoxit. Sandpaper can destroy the coating of the contacts.
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On one of my 2200's, one of the indicated caps went bad, causing R417 to go up in smoke, and the protection circuit to engage. These units are old, and the caps probably should be replaced. Replacing the largest 4 caps may need to be done, but there are no direct replacements. Search and read the threads about alternatives.
 
I cleaned the relays and now I'm not getting any sound, not even a clicking from the relays. I think I'm going to replace them.
 
I cleaned the relays and now I'm not getting any sound, not even a clicking from the relays. I think I'm going to replace them.
If you're not getting a clicking thats more likely to mean that the protect circuit is preventing them from engaging - unless you damaged them when you cleaned them.
 
...it was in protection mode....is there a common problem with them...

Yep. I'd say most NAD 2200s have spent some or all of their time in protection mode. They are a touchy design and most end up vaporising an output stage or two. Commutating rails and a +/-90v min supply so be careful poking around.
 
Don't spray contact cleaner or Deoxit willy-nilly into the tops of the relays - it does more harm than good. I honestly believe the best way to take care of bad relays is to replace them, but yours are not engaging because the unit is in protect mode. NAD used excellent circuit designs, but kept the costs low by using cheap parts and cheap labor. Check to see if you have excessive DC offset on the speaker terminals. Download the service manual and start checking voltages.
 
Still, not a bad idea to check the DC offset measured before the signal goes into the relays. If offset measured is in the low mV level, then it could just be buggered relays. A decent target is < 100mV. If you get a much higher reading, things could be starting to go south. According to the video, you should change the resistor as well.
 
Its not in protection mode now just no sound and the relays don't click.

I repaired a NAD 3100 with the same issue for a friend. The relays were stuck open. A few solid taps with the back of a screwdriver and they popped on.
 
Ordered new relays today, Do I need to replace the the resistor in between them with a 240 ohm 2 watt? or is it with that brand?



https://www.mouser.com/ProductDetail/653-G2R-24-DC24

The resistor value will depend on the resistance of the new relay coil. You want to drop 22v across each of the relay coils. Ohms law to get the current of the circuit with the new relays then use the current to figure the resistance to drop the rest of the supply voltage across R413. Do a google search for the service manual. The manual will also give you the correct values for bias and DC offset.
The relay you ordered doesn't have the correct pin outs or footprint to work. The current rating is not enough either, IMO (only 5A). I used the relays you bought in my 50wpc NAD 2100.
I used these http://www.newark.com/imo-precision...dc/relay-automotive-spdt-14vdc-45a/dp/74R1551 in my 2600A which has the same protection circuit layout as your 2200 as in the video above.
The 240 ohm 2w resistor would be used with the IMO relays.
 
The resistor value will depend on the resistance of the new relay coil. You want to drop 22v across each of the relay coils. Ohms law to get the current of the circuit with the new relays then use the current to figure the resistance to drop the rest of the supply voltage across R413. Do a google search for the service manual. The manual will also give you the correct values for bias and DC offset.
The relay you ordered doesn't have the correct pin outs or footprint to work. The current rating is not enough either, IMO (only 5A). I used the relays you bought in my 50wpc NAD 2100.
I used these http://www.newark.com/imo-precision...dc/relay-automotive-spdt-14vdc-45a/dp/74R1551 in my 2600A which has the same protection circuit layout as your 2200 as in the video above.
The 240 ohm 2w resistor would be used with the IMO relays.

I looked at the pictures and they are all deferent but I did get it from this thread and he did replace the resistor. I did buy it from both places.
http://audiokarma.org/forums/index.php?threads/nad-2200-help.265844/

and your correct the part number on the other thread is incorrect.
 
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Replaced the relays and fired it up. the units been running smooth for hours. I notice on the wiring diagram the rail voltage in +95v wow. should I go back a check the voltages?
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