Hi,
I have an NAD 326bee, which has been great for a few years until it suddenly started making a strange static noise through the left channel. I read a few posts here about similar issues, but I could use help on what to try next.
The issue:
-- The issue first came with a loud-ish 'pop' sound, which happened only once, and now continues to have a low-medium volume 'white noise' static on the left channel only. The 'pop' makes me worry some component blew, but I have no idea which one.
-- Static is completely independent of volume or tone knobs - it happens with volume all the way down too. I can still play music and adjust music volume, but static persists constantly in the left channel.
-- Occurs through both headphones and speakers
What I've done so far, which has not resolved the issue:
-- Cleaned main power switch and pre/power amp jumpers with contact cleaner
-- Inspected for bad solder joints, fixing 2 that looked cold.
-- Unplugged and replugged several connectors on the main board that were easily accessible
-- Pressed on various components in the protection circuit area with a non-conductive probe to see if I could isolate anything.
Not sure where to go from here...
If it helps, I have noticed twice in the past that the amp has shut itself off (likely triggering the protection circuit?) for no apparent reason at relatively low volume. I was able to turn it on again by turning off the main switch and then powering the amp up again after a few seconds.
Thanks so much!
I have an NAD 326bee, which has been great for a few years until it suddenly started making a strange static noise through the left channel. I read a few posts here about similar issues, but I could use help on what to try next.
The issue:
-- The issue first came with a loud-ish 'pop' sound, which happened only once, and now continues to have a low-medium volume 'white noise' static on the left channel only. The 'pop' makes me worry some component blew, but I have no idea which one.
-- Static is completely independent of volume or tone knobs - it happens with volume all the way down too. I can still play music and adjust music volume, but static persists constantly in the left channel.
-- Occurs through both headphones and speakers
What I've done so far, which has not resolved the issue:
-- Cleaned main power switch and pre/power amp jumpers with contact cleaner
-- Inspected for bad solder joints, fixing 2 that looked cold.
-- Unplugged and replugged several connectors on the main board that were easily accessible
-- Pressed on various components in the protection circuit area with a non-conductive probe to see if I could isolate anything.
Not sure where to go from here...
If it helps, I have noticed twice in the past that the amp has shut itself off (likely triggering the protection circuit?) for no apparent reason at relatively low volume. I was able to turn it on again by turning off the main switch and then powering the amp up again after a few seconds.
Thanks so much!
Experienced solder operators have an ability to make good looking solder joints that don't make connection all the time. I've repaired a few in 80's 90's products.
You're going to need to check the unit with the power on, so first, basic safety training for new repairmen. Use only one hand at a time. Voltage >25 across your heart can stop it. Checking voltages, connect the negative of DVM to analog ground (like speaker ground) with an alligator clip lead, with one hand. Then with the same hand probe around for voltage. If you have to measure voltage across a component, write down both readings then subtract.
Wear no jewelry on hands, wrists, or neck. 1 v at high current through a ring can burn your flesh to charcoal.
Wear safety glasses with power on or especially desoldering. Solder splashes, parts explode sometimes.
It is best to not work alone. Don't work distracted by entertainment or conversation.
Okay, to find a bad joint or resistor with a bad internal weld causing noise, turn the unit on with the cover off & connected to a speaker. Figure out which side is the left by tracing the speaker jack wire back to the PCB. Take a wooden stick, like a chop stick or a dried up plastic stick pen. Push on the components starting at the output transistors then working back through the drivers and the small input transistors. Resistors are more likely to make this noise than transistors, but any solder joint is suspect. If the noise changes while you are pushing on a component, there is your problem. This search includes connectors betweeen boards and to front panel components and back.
If that doesn't work, you may have to take a scope or sound probe and work through the circuit from back to front finding out where the noise stops. Between two places, on with noise and one without noise, in between is your bad part bad weld or bad solder joint.
As far as protection, NAD tends to use a uPC protection IC which has 3 inputs, all with electrolytic caps connected. These caps can get leaky after 20 years and put the unit into protection mode without due cause. If replacing e-caps, buy the ones rated >3000 hours service life. 500 hour caps from the shelf of the TV parts store can need replacing again in < a year. You can get 10000 hour caps in the smaller sizes. Higher temp rating multiplies the service life, as a 10000 hour 105 deg C part will likely outlast a 10000 hour 85 deg C part. In US, Newark & Digikey put the service life in the selector table if you ask for it. Mouser makes you download datasheet on every cap. Other distributors won't tell you what they are selling by manufacturer & part #. I don't buy e-caps from them. ebay & alibaba are refuges for old caps that didn't sell within the shelf life.
Happy hunting.
You're going to need to check the unit with the power on, so first, basic safety training for new repairmen. Use only one hand at a time. Voltage >25 across your heart can stop it. Checking voltages, connect the negative of DVM to analog ground (like speaker ground) with an alligator clip lead, with one hand. Then with the same hand probe around for voltage. If you have to measure voltage across a component, write down both readings then subtract.
Wear no jewelry on hands, wrists, or neck. 1 v at high current through a ring can burn your flesh to charcoal.
Wear safety glasses with power on or especially desoldering. Solder splashes, parts explode sometimes.
It is best to not work alone. Don't work distracted by entertainment or conversation.
Okay, to find a bad joint or resistor with a bad internal weld causing noise, turn the unit on with the cover off & connected to a speaker. Figure out which side is the left by tracing the speaker jack wire back to the PCB. Take a wooden stick, like a chop stick or a dried up plastic stick pen. Push on the components starting at the output transistors then working back through the drivers and the small input transistors. Resistors are more likely to make this noise than transistors, but any solder joint is suspect. If the noise changes while you are pushing on a component, there is your problem. This search includes connectors betweeen boards and to front panel components and back.
If that doesn't work, you may have to take a scope or sound probe and work through the circuit from back to front finding out where the noise stops. Between two places, on with noise and one without noise, in between is your bad part bad weld or bad solder joint.
As far as protection, NAD tends to use a uPC protection IC which has 3 inputs, all with electrolytic caps connected. These caps can get leaky after 20 years and put the unit into protection mode without due cause. If replacing e-caps, buy the ones rated >3000 hours service life. 500 hour caps from the shelf of the TV parts store can need replacing again in < a year. You can get 10000 hour caps in the smaller sizes. Higher temp rating multiplies the service life, as a 10000 hour 105 deg C part will likely outlast a 10000 hour 85 deg C part. In US, Newark & Digikey put the service life in the selector table if you ask for it. Mouser makes you download datasheet on every cap. Other distributors won't tell you what they are selling by manufacturer & part #. I don't buy e-caps from them. ebay & alibaba are refuges for old caps that didn't sell within the shelf life.
Happy hunting.
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