NAD C 320 DC-Offset Questions?
So I've just replaced a 230v NAD C-320BEE with a correct NAD 120v transformer.
The wiring of a new two-pronged polarized male plug end is the final step, but I'm not sure that I can just wire the new plug end willy-nilly.
Question:
1.) Does it matter?
2.) If so? How do I determine which one of the two transformer primary mains wiring is the neutral wire versus the 120v hot side.
TIA
So I've just replaced a 230v NAD C-320BEE with a correct NAD 120v transformer.
The wiring of a new two-pronged polarized male plug end is the final step, but I'm not sure that I can just wire the new plug end willy-nilly.
Question:
1.) Does it matter?
2.) If so? How do I determine which one of the two transformer primary mains wiring is the neutral wire versus the 120v hot side.
TIA
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Wide prong is the neutral, so use the white wire of the cord and of the transformer.
Narrow prong is the hot, so use the black wire of the cord and of the transformer.
Narrow prong is the hot, so use the black wire of the cord and of the transformer.
This I understand Rayma, but how do I determine which of the two wires coming from the transformers primary side are the hot and neutral?
My thinking is it really doesn't matter for the power is being fed into a transformer internally to reduce the voltage as the connections really shouldn't matter which way around they go.
But I just want to make sure from a safety stand point.
And a simple comprehensive color coding for USA single/3 phase and UK single/3 phase -
Wiring Color Codes - USA, UK, Europe & Canada Codes, When to Apply
Unless you are dealing with transformer primary/secondary tappings it doesn't matter which way round a single input/output goes .
https://www.electronics-tutorials.ws/transformer/transformer-basics.html
Wiring Color Codes - USA, UK, Europe & Canada Codes, When to Apply
Unless you are dealing with transformer primary/secondary tappings it doesn't matter which way round a single input/output goes .
https://www.electronics-tutorials.ws/transformer/transformer-basics.html
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If the primary transformer wires are not white or black, then they are interchangeable either way.
But the wiring colors should be consistent if they are.There's no electrical difference between the
two wires of a two wire primary, regardless. Sometimes there are taps, or a dual primary, though.
But the wiring colors should be consistent if they are.There's no electrical difference between the
two wires of a two wire primary, regardless. Sometimes there are taps, or a dual primary, though.
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The two input primary wiring colors for the transformers (both the 120v & 230v) are brown and blue.
Correct me if I'm wrong, but would the brown represent (hot) and the (blue) neutral?
There's no standard, and often both primary wires are black. In any event,
if there are only two primary wires, they are electrically interchangeable.
if there are only two primary wires, they are electrically interchangeable.
Got it from the very informative link Duncan posted.
Wiring Color Codes in Europe (IEC) for AC Supply
Wire Color Codes in Europe (IEC) for AC supply are as follows:
Single Phase, Line (Hot) – Brown
3 Phase, Line 1 – Brown
3 Phase, Line 2 – Black
3 Phase, Line 3 – Grey
Neutral – Blue
Ground – Green with Yellow Stripe
Thanks for the help everyone.
Amp is up and living on 120v ac now.
Going to let it sit idle with power on for a while and then trim out the bias and dc-offset settings.
Wiring Color Codes in Europe (IEC) for AC Supply
Wire Color Codes in Europe (IEC) for AC supply are as follows:
Single Phase, Line (Hot) – Brown
3 Phase, Line 1 – Brown
3 Phase, Line 2 – Black
3 Phase, Line 3 – Grey
Neutral – Blue
Ground – Green with Yellow Stripe
Thanks for the help everyone.
Amp is up and living on 120v ac now.
Going to let it sit idle with power on for a while and then trim out the bias and dc-offset settings.
FWIW in Argentina Blue is Hot and Brown is Neutral but I think it´s opposite to other Countries.
My point not being "it doesn´t matter because AC is AC" but that it´sensible to follow local Code reccomendations.
Now if colours do not match, say local Code uses Black and White and you have Blue and Brown, yes, in that case flip a coin.
My point not being "it doesn´t matter because AC is AC" but that it´sensible to follow local Code reccomendations.
Now if colours do not match, say local Code uses Black and White and you have Blue and Brown, yes, in that case flip a coin.
Quick question for anybody who’s familiar with the alignment of the NAD C320BEE amplifier.
On the DC-Offset the service manual states that the adjustment value is between 0v+ and -30v.
I’m getting fluctuating voltages on both speaker outputs that are reading between -06.0v to +00.4v.
Idling current is pretty stable on both channels of +3.8v for the left and +3.6v for the right.
Is that bouncing around on the dc-offset considered normal operation for this amplifier.
Kind regards,
On the DC-Offset the service manual states that the adjustment value is between 0v+ and -30v.
I’m getting fluctuating voltages on both speaker outputs that are reading between -06.0v to +00.4v.
Idling current is pretty stable on both channels of +3.8v for the left and +3.6v for the right.
Is that bouncing around on the dc-offset considered normal operation for this amplifier.
Kind regards,
These figures are for idle or on load?
You used a digital or analog meter?
DC should be below 0.5 volts in other amps, this needs confirming by other members.
You used a digital or analog meter?
DC should be below 0.5 volts in other amps, this needs confirming by other members.
Hi Naresh,
Digital multimeter and amp has been on and idling with no load over the past 24 hours.
My concern is with the constant fluctuations in the dc-offset.
The service manual stipulates that the dc-offset is between +0v and -30 millivolts. Makes no mention of an actual target number so I was hoping some NAD guru could chime in and confirm that what I’m seeing as numbers fluctuating is normal for this particular amplifier.
"No load " ? then you either have a thermal heating problem ( balance ) at an input active device or that's the way its designed.
Hi Duncan,
A simple search I performed on the internet reveals nothing in regards to what the ideal dc-offset setting for this amp should be.
I find it rather vague that the service manual only states that you turn the unit on and adjust the voltage regulating trim pots to get a reading of 0v+/-30mv
I can only conclude from that a reading anywhere between 0v+/-30mv is fine (including a fluctuating reading too) as long as it stays below 0v+.
The ideal offset is 0V. In practise without a servo the DC offset will drift, but it doesn't matter as long as it's less than 0.05V or so.
If your offsets are bouncing around a lot something's wrong. First eliminate dry joints (look for evidence of heat on the legs of the driver transistor - the solder joints commonly fail there), then try some freezer spray on the small transistors in the driver stage and/or input stage one at a time to see if that shows up faulty devices.
If your offsets are bouncing around a lot something's wrong. First eliminate dry joints (look for evidence of heat on the legs of the driver transistor - the solder joints commonly fail there), then try some freezer spray on the small transistors in the driver stage and/or input stage one at a time to see if that shows up faulty devices.
Hi John,
I have a YouTube video link below to illustrate what is going on with DC-offset. This is on the left channel, but the right channel is approximating the same variations in the voltage readings too.
July 16, 2021 NAD C320BEE - YouTube
Yes Benjisan it does state it can vary up to 30mv so that is the design specifications .
If you get the same on both channels then its a design "feature " , I am more used to using high quality active devices that are specified as "matched pairs " or running through many components till I find two with equal gain ( or near it ) this makes it easier in the choice and number of components required to make a final adjustment .
If you get the same on both channels then its a design "feature " , I am more used to using high quality active devices that are specified as "matched pairs " or running through many components till I find two with equal gain ( or near it ) this makes it easier in the choice and number of components required to make a final adjustment .
Well I appreciate all your input guys.
Just as a follow up to John’s suggestions of the possibility of a bad solder joints. I removed the back cover to expose the bottom of the pcb and wasn’t able to see any signs of obvious dry or damaged solder joints.
I don’t have any aerosol freeze spray, but I have a infrared temperature gun that I could put to use if it would help in determining any bad components.
I also have an oscilloscope that I know how to use, but I’m not skilled enough in electronics with regards to the understanding of schematics and what voltages to view and test.
I wonder if it would make more sense to create a new thread in this forum that could garner more attention from those members who are more familiar with this particular amplifier.
Just as a follow up to John’s suggestions of the possibility of a bad solder joints. I removed the back cover to expose the bottom of the pcb and wasn’t able to see any signs of obvious dry or damaged solder joints.
I don’t have any aerosol freeze spray, but I have a infrared temperature gun that I could put to use if it would help in determining any bad components.
I also have an oscilloscope that I know how to use, but I’m not skilled enough in electronics with regards to the understanding of schematics and what voltages to view and test.
I wonder if it would make more sense to create a new thread in this forum that could garner more attention from those members who are more familiar with this particular amplifier.
Hopefully, the bias testing is done with the input jacks shorted out, to eliminate any stray interferences from nearby.
A fluctuating bias level could be caused by leakage in capacitors, thermal issues with resistors, and junction issues in transistors, as well as fluctuating line voltage.
A fluctuating bias level could be caused by leakage in capacitors, thermal issues with resistors, and junction issues in transistors, as well as fluctuating line voltage.
Hi wiseoldtech,
Although the service manual doesn’t state it, but I had shorted the input jacks and it made no difference at all. Not sure if this is relevant, but the idle current is very stable between TP1, TP2, TP3, and 4.