Always! First point to check when both channels have same problem, the _power supply_ Caps first, rectifiers second and voltage regulators. Then, overheated / cooked resistors etc. Thanks for the video!
Hello. Thank you very much for this video which allowed me to troubleshoot my NAD C272! I had the exact same symptom! (no -68V and very bad sound) I replaced : Transistors Q712 and Q709 Resistors R724 and R722 Capacitor C279 My amp is working great now! Thanks again!
Your technique is very good. What I really like is that you show the actual circuit and also show the schematic diagram for that portion under test / evaluation.
Great troubleshooting. I sold NAD for years. I had a 7400 and 2400, and loved them. Great designs but allot of corners cut in costs. NAD had a rather high defect rate with us. The Master Series was excellent. No issues. But the Classic or Theater models always gave me pause when I sold them whether of not they would come back defective. If they didn't you would be good for some time. If it came back it had either something silly or serious wrong with it. The cheap capacitors don't help. It could also be the rather ambitious design especially in light of the power envelope circuit while ingenious could be problematic. The made in China NAD was more failure prone than the Japan models but some of the Monitor series which this amplifer is related too could be troublesome too. This amplifier is not that old and component failure like this should not be happening.
Quick Tip: If the issue is on both (or all) amplification circuits, then you're problem 99% of the time is a circuit that is common to the amplifier boards...start there. I had an issue with a NAD 2200 with a DC voltage spike on both channels upon power-off and it wound up being the IC protection chip not dis-engaging the speaker relay's fast enough.
I just found your channel, But I really like the videos of your talents at fixing audio dear, so I subscribed after only watching 4 videos. Thank you for sharing what you do, I find it very interesting and educational.
I think I may have the exact same problem with mine. Cuts out/distort the sound and even ruind some of my speakers. Will have to ohm them to see how many. And gonna open and see if it looks the same or any bad parts. Im not skilled in this, but know alittle and have soderd alto. So If I just can get what components that need to be swapped, it should be ok. Realy nice video!
I just got one in exactly same model, it seem to work : Amp boards R444, R434 R334 R344 gets red glowing hot !! Power board ( the large in the bottom ) R734 R738 Q712 also get alarmingly hot.. but the amp is working, this cant be normal, components over 140 C right after power on, it idle at 46W mains input 230V
Hello, always great content. Have you ever worked on a Threshold power amp? I have an S/300 power amp that is about 30 years old and the right channel positive rail fuse has recently blown. What things should I look at to diagnose the problem? Is this something that you would be interested in repairing? I opened up the cover and everything looks in the same great condition that it did from 30 years ago. Regards, John
Hi John, I have no experience with Threshold amps. Since the positive rail fuse blew, I would suspect that one or more components being fed by the positive rail has shorted. I'd be interested in working on it if you're willing to ship it. Looks like a large and heavy amp so it might be expensive. Feel free to email me. nick@duality-er.com
good evening, perfect video, hat down, I wanted to ask, the signal generator, connects classically from the back of the amplifier, to how many inputs, or they connect directly somewhere on the board🤔🤔 Thank you
This looks exactly like the same issue i am working on with a C370!!, same circuit, same 3 toasted resistors. However no blown capacitor that i noticed, and also I had a fusible resistor in that place that blew. And i've seen other people have this issue also in this area, in various similar models. One guy even had the area with the 3 resistors burnt thru the PCB. I've nearly fixed mine I think, now it can actually start, but plays extremely low sound. hoping replacing the 4 large caps will do it, replaced all others.
@@chickenfizz omg... user error.... in a lot of my testing i had been using my cell phone and audio jack in it......... now i tried a more proper source, and what do you know, i probably fixed it long ago. Now just to repair the stuff i broke trying to fix it.
Great video thank you. As I'm just starting out it would have been really useful to see how and where you connected the probes to the inputs/outputs. Also, I notice you don't use a load when turning the volume up. Is it OK to do that with larger, bridged power amps (240w p/c)?
Nad seems bad in terms of quality, i had c375bee it Broke down in just 5 years, it sounded good and powerful for the money through, got hegel h190 instead much better amp in every way, Deeper and better bass control Better detailed sound, Don’t sound as stressed as the nad did.when pushed
I bought one of these units used, sounds good, no issues so far, but I am aware of some of the caps blowing up via NAD's bulletin from the mid 2000s. Should I be worried? My unit was made in 2004.
Although 16 years isn’t all that long, original caps are always a concern. Especially if they are poor quality and the amp is used often. It wouldn’t hurt to remove the cover and visually inspect them all. If any of them are bulged or leaking, I would consider having the unit recapped. Even if you don’t see evidence of failure, it’s still a good idea to recap as that will improve the longevity of the unit.
@@dualityrepair4770 Well that didn't take long. after about a week using this amp for my front left/right speakers in a 5.1 setup, suddenly last night the output from those two speakers cut in half & when pushed with volume, produced a fizzy distortion. I unhooked my receiver & tried another device directly into the amp with the same results. Any idea what the issue is specifically & what I might be looking at for repair costs? Thanks
Since it was both outputs at the same time, I’d suspect something in the power supply... likely caps. No idea what other people charge. You could always send it to me. You’d pay shipping and parts, never any service charge.
I've never been onboard with recapping everything for the hell of it like some people do, but having witnessed catastrophic failure on that board, I think I'd assume the other electrolytics aren't long for this world.
I half agree but myself anything pre 1990 really should be a candidate for recapping especially if it’s had some hours on its electronics. Wouldn’t say all kit but especially designs that run hot or usually driven hard to get its best.
Hi and thanks for this video. Can you please explain how did you manage to take out the power transistors from the heat sink? I removed all screws with alen key etc but they did not get loose..... thanks again
MED DUB - Did you find the answer to how to separate the power amp board from the heat sink? I'm facing the same issue right now. Could Dualiy Repair help out? Thank you!
Sorry to say this but a technician of your caliber does not check all rail voltages even after getting distortion in both channels is a bit hard to digest. Sorry don't agree.
Ever consider to use a signaltracer to find the culprit part ? An old pc speakerset can do the job, to give you an idea, take a look at this video : ua-cam.com/video/PZoZ0x4ISKQ/v-deo.html
I am located in Minnesota. If you happen to be in the twin cities you could stop by. Otherwise, if you have something you’d like me to look at, you can email me at nick@duality-er.com with the details.
Always!
First point to check when both channels have same problem, the _power supply_
Caps first, rectifiers second and voltage regulators. Then, overheated / cooked resistors etc.
Thanks for the video!
Hello.
Thank you very much for this video which allowed me to troubleshoot my NAD C272!
I had the exact same symptom! (no -68V and very bad sound)
I replaced :
Transistors Q712 and Q709
Resistors R724 and R722
Capacitor C279
My amp is working great now!
Thanks again!
Your technique is very good. What I really like is that you show the actual circuit and also show the schematic diagram for that portion under test / evaluation.
Great troubleshooting. I sold NAD for years. I had a 7400 and 2400, and loved them. Great designs but allot of corners cut in costs. NAD had a rather high defect rate with us. The Master Series was excellent. No issues. But the Classic or Theater models always gave me pause when I sold them whether of not they would come back defective. If they didn't you would be good for some time. If it came back it had either something silly or serious wrong with it. The cheap capacitors don't help. It could also be the rather ambitious design especially in light of the power envelope circuit while ingenious could be problematic. The made in China NAD was more failure prone than the Japan models but some of the Monitor series which this amplifer is related too could be troublesome too. This amplifier is not that old and component failure like this should not be happening.
Quick Tip: If the issue is on both (or all) amplification circuits, then you're problem 99% of the time is a circuit that is common to the amplifier boards...start there. I had an issue with a NAD 2200 with a DC voltage spike on both channels upon power-off and it wound up being the IC protection chip not dis-engaging the speaker relay's fast enough.
I just found your channel, But I really like the videos of your talents at fixing audio dear, so I subscribed after only watching 4 videos. Thank you for sharing what you do, I find it very interesting and educational.
Nice work. Was scratching my head when you first moved away from measuring the voltages but you eventually got back to it. 👍
Must admit I was thinking that the negative supply rail might be dodgy. I was always taught check voltages.
@@Catstorm99 unless it keeps blowing fuses, and powering might damage more.
@@pvb9964 very true.
Great video and nice troubleshooting! :)
Fortunately, my C272 is in good shape and does its job excellently.
I bought a broken C272 a couple years ago and it turned out to be a very nice sounding amplifier. Deep soundstage, very robust.
Someday I’ll get decent speakers so I can fully appreciate the nicer amps like this that I repair.
@@dualityrepair4770 I was using the elac unifi's and they matched pretty good with the NAD sound.
@@dualityrepair4770 NAD do sound good when working which is around 1 hour every 3 years. lol. The build quality was atrocious.
Thank you for taking the time to do these fascinating videos. Great work sir
Electronics fault finding 101: check power supplies!
You are a great teacher love the videos
NAD used a lot of cheap, Chinese caps in these amps back in the day. Best to just replace them all with quality parts.
Well that's more than 90% of amps covered then.
I think I may have the exact same problem with mine. Cuts out/distort the sound and even ruind some of my speakers. Will have to ohm them to see how many. And gonna open and see if it looks the same or any bad parts. Im not skilled in this, but know alittle and have soderd alto. So If I just can get what components that need to be swapped, it should be ok.
Realy nice video!
Well done, learn a lot from this video. Thanks you sir.
Well done. Super video - very educating
Very good video and excellent explanation, I learned a lot from this video.thanks
Well done. I wouldnt even know where to start!
Very clear and informative video. sub'ed
I just got one in exactly same model, it seem to work : Amp boards R444, R434 R334 R344 gets red glowing hot !! Power board ( the large in the bottom ) R734 R738 Q712 also get alarmingly hot.. but the amp is working, this cant be normal, components over 140 C right after power on, it idle at 46W mains input 230V
Fascinating, thank you for the video!
Excellent video and repair!
good job sir, a very good repair video. I enjoyed it.
Great work but very low microphone, can barely hear you.
Hello, always great content. Have you ever worked on a Threshold power amp? I have an S/300 power amp that is about 30 years old and the right channel positive rail fuse has recently blown. What things should I look at to diagnose the problem? Is this something that you would be interested in repairing? I opened up the cover and everything looks in the same great condition that it did from 30 years ago. Regards, John
Hi John,
I have no experience with Threshold amps. Since the positive rail fuse blew, I would suspect that one or more components being fed by the positive rail has shorted. I'd be interested in working on it if you're willing to ship it. Looks like a large and heavy amp so it might be expensive. Feel free to email me. nick@duality-er.com
Rotel are who NAD wanted to be.... They never came close. NAD always were poorly manufactured rubbish and grossly over priced.@@dualityrepair4770
good evening, perfect video, hat down, I wanted to ask, the signal generator, connects classically from the back of the amplifier, to how many inputs, or they connect directly somewhere on the board🤔🤔 Thank you
This looks exactly like the same issue i am working on with a C370!!, same circuit, same 3 toasted resistors. However no blown capacitor that i noticed, and also I had a fusible resistor in that place that blew. And i've seen other people have this issue also in this area, in various similar models. One guy even had the area with the 3 resistors burnt thru the PCB.
I've nearly fixed mine I think, now it can actually start, but plays extremely low sound. hoping replacing the 4 large caps will do it, replaced all others.
Very little chance that replacing the 4 large filter caps will make any difference to the gain. I think you have a problem elsewhere.
@@chickenfizz omg... user error.... in a lot of my testing i had been using my cell phone and audio jack in it......... now i tried a more proper source, and what do you know, i probably fixed it long ago. Now just to repair the stuff i broke trying to fix it.
Great video thank you. As I'm just starting out it would have been really useful to see how and where you connected the probes to the inputs/outputs. Also, I notice you don't use a load when turning the volume up. Is it OK to do that with larger, bridged power amps (240w p/c)?
fine business BUDDY
Nice work
Nad seems bad in terms of quality, i had c375bee it Broke down in just 5 years, it sounded good and powerful for the money through, got hegel h190 instead much better amp in every way,
Deeper and better bass control
Better detailed sound,
Don’t sound as stressed as the nad did.when pushed
Great video !
Nicely done.
Thanks!
Nice job
Do you have a reliable place that you can get your schematics from online
I bought one of these units used, sounds good, no issues so far, but I am aware of some of the caps blowing up via NAD's bulletin from the mid 2000s. Should I be worried? My unit was made in 2004.
Although 16 years isn’t all that long, original caps are always a concern. Especially if they are poor quality and the amp is used often. It wouldn’t hurt to remove the cover and visually inspect them all. If any of them are bulged or leaking, I would consider having the unit recapped. Even if you don’t see evidence of failure, it’s still a good idea to recap as that will improve the longevity of the unit.
@@dualityrepair4770 Well that didn't take long. after about a week using this amp for my front left/right speakers in a 5.1 setup, suddenly last night the output from those two speakers cut in half & when pushed with volume, produced a fizzy distortion. I unhooked my receiver & tried another device directly into the amp with the same results. Any idea what the issue is specifically & what I might be looking at for repair costs? Thanks
Since it was both outputs at the same time, I’d suspect something in the power supply... likely caps. No idea what other people charge. You could always send it to me. You’d pay shipping and parts, never any service charge.
was that actually a blown up transistor we were looking at towards the end there when you isolated the problem? Great video.
What real power?
I've never been onboard with recapping everything for the hell of it like some people do, but having witnessed catastrophic failure on that board, I think I'd assume the other electrolytics aren't long for this world.
I half agree but myself anything pre 1990 really should be a candidate for recapping especially if it’s had some hours on its electronics. Wouldn’t say all kit but especially designs that run hot or usually driven hard to get its best.
Nad built these with garbage caps. expect them to last 10-15yrs at most. Recapping NADs is manditory
Hi and thanks for this video. Can you please explain how did you manage to take out the power transistors from the heat sink? I removed all screws with alen key etc but they did not get loose..... thanks again
MED DUB - Did you find the answer to how to separate the power amp board from the heat sink? I'm facing the same issue right now. Could Dualiy Repair help out? Thank you!
Hi. Do you know where I can buy vintage hifi, such as sony lbt v902, sony mhc 551, etc, online in the US? THX
Sorry to say this but a technician of your caliber does not check all rail voltages even after getting distortion in both channels is a bit hard to digest. Sorry don't agree.
Wow
I thought you said it is not power supply issue , well you were wrong !!
nice work! what pre amp would you recommend combinig with this amp?
Unfortunately amp matching is outside my field of experience.
Ever consider to use a signaltracer to find the culprit part ?
An old pc speakerset can do the job, to give you an idea, take a look at this video :
ua-cam.com/video/PZoZ0x4ISKQ/v-deo.html
MAY I KNOW ABOUT YOUR SHOP? WHERE ARE LOCATED? THANK YOU.
I am located in Minnesota. If you happen to be in the twin cities you could stop by. Otherwise, if you have something you’d like me to look at, you can email me at nick@duality-er.com with the details.
No good take time forever...
So does your mom but who cares
Oh yes, your mic level is a bit low. I have trouble hearing you.
Hi. Do you know where I can buy vintage hifi, such as sony lbt v902, sony mhc 551, etc, online in the US? THX