Hey, I am very new to repairing electronics with capacitors as well as using a multimeter so I need so help/guidance fixing this issue
recently I was handed a family members old NAD C320BEE that they had in their loft for storage for a few years but when powered on it went into power safety mode due to a problem on the protection circuit somewhere before it went into storage I was told it worked fine I found lots of people online talking about how the capasitors are known to be pretty bad in this model and can cause this issue the only problem being I don't have much experience sorting this so I thought it might be a good opportunity to learn I found the online schematics for the board although I don't really know how to read them and tried checking some power levels around the board the power from the power supply mini board seemed correct but the +18 and -18 rail seemed to be incorrect from what I could figure out so I tried to check the capacitance of a lot of the capasitors on the board and I'm not too sure if I've found the issue or not the following capacitors stood out more than the rest but lots were slightly out of spec so I'm not sure how to take it if they need replacing or not:
C431 0.75mf instead of 10uf
C430 13.36mf instead of 10uf
C12 111.4uf instead of 47uf
C326 and c325 0.46mf instead of 47uf
C421 580mf instead of 4.7uf
C49 104900uf instead of 47uf
C47 860uf instead of 47uf
C413 and c414 350uf instead of 220uf
C48 1280mf instead of 47uf
C410 170uf instead of 47uf
C342 250uf instead of 47uf
C425 1.8mf instead of 2.2mf
C436 is 0.25mf instead of 100uf
C324 is 10.74mf instead of 47uf
C323 is 450uf instead of 47uf
C44 is 610uf instead of 220uf
C43 is 1.43mf instead of 220uf
C26 is OL on max settings should be 220uf
C25 is 18.4mf instead of 220uf
C15 is 13.6mf instead of 220uf
C16 is 14.26mf instead of 220uf
as I said I'm not experienced at all with this type of stuff so would be really appreciated for any guidance that you could give I'm not sure how big of an error of margin I should give c410 doesn't seem too far off but its still 3x over what it should be so should it be replaced or is it an issue further back down the line that is making this capacitor seem broken I'm not sure and don't really know where I should go
TL;DR
I need help fixing a NAD C320BEE but don't have much experience with electronics and don't know what to do
recently I was handed a family members old NAD C320BEE that they had in their loft for storage for a few years but when powered on it went into power safety mode due to a problem on the protection circuit somewhere before it went into storage I was told it worked fine I found lots of people online talking about how the capasitors are known to be pretty bad in this model and can cause this issue the only problem being I don't have much experience sorting this so I thought it might be a good opportunity to learn I found the online schematics for the board although I don't really know how to read them and tried checking some power levels around the board the power from the power supply mini board seemed correct but the +18 and -18 rail seemed to be incorrect from what I could figure out so I tried to check the capacitance of a lot of the capasitors on the board and I'm not too sure if I've found the issue or not the following capacitors stood out more than the rest but lots were slightly out of spec so I'm not sure how to take it if they need replacing or not:
C431 0.75mf instead of 10uf
C430 13.36mf instead of 10uf
C12 111.4uf instead of 47uf
C326 and c325 0.46mf instead of 47uf
C421 580mf instead of 4.7uf
C49 104900uf instead of 47uf
C47 860uf instead of 47uf
C413 and c414 350uf instead of 220uf
C48 1280mf instead of 47uf
C410 170uf instead of 47uf
C342 250uf instead of 47uf
C425 1.8mf instead of 2.2mf
C436 is 0.25mf instead of 100uf
C324 is 10.74mf instead of 47uf
C323 is 450uf instead of 47uf
C44 is 610uf instead of 220uf
C43 is 1.43mf instead of 220uf
C26 is OL on max settings should be 220uf
C25 is 18.4mf instead of 220uf
C15 is 13.6mf instead of 220uf
C16 is 14.26mf instead of 220uf
as I said I'm not experienced at all with this type of stuff so would be really appreciated for any guidance that you could give I'm not sure how big of an error of margin I should give c410 doesn't seem too far off but its still 3x over what it should be so should it be replaced or is it an issue further back down the line that is making this capacitor seem broken I'm not sure and don't really know where I should go
TL;DR
I need help fixing a NAD C320BEE but don't have much experience with electronics and don't know what to do
Attachments
Some people manage to repair a vintage amp by replacing all the caps but success is not certain. You might do a lot of work and find the amp is still not good enough or does not work at all. For example, I repaired the C320bee a couple of times but it became intermittent with random volume fluctuations. I replaced the mainboard with 3886 modules.
The 320 18v regulators run hot because it shares the +-36vdc with the amplifier circuits. Also there is poor ventilation. It is not reliable.
Good news. There are plenty of sensible DIY projects worth your time.
Hi Alfieh,
If you decide to attempt this, a couple pointers.
If you can't / won't do the above, take it to a trained service technician. If not, give it to someone who will fix it properly.
If you decide to attempt this, a couple pointers.
- Do not buy a "capacitor kit" or rebuild kit" for this unit.
- Purchase the replacement parts from authorized distributors.
- Pay attention to component lead spacing and voltage ratings. Your replacement caps will probably be higher voltage.
- If the leads are too close together, support the lead as it comes out, bend it, then support it at the bend and bend it straight. Allowing the leads to bend outwards may damage the seals
- Use a controlled temperature soldering station.
If you can't / won't do the above, take it to a trained service technician. If not, give it to someone who will fix it properly.
NAD is owned by Chinese entities now, and was a junk brand all the time, more a poseur selling on advertising hype rather than real quality.
Their main market was UK, a little in USA, but the Japanese sets killed them their on sheer quality and price.
A member here, ex Akai tech, ex-moderator, says he has rarely seen such poor quality, and named Bluesound as well in that category.
They are tricky, and tend to be race car like, need maintenace too often.
Best to build another, better result, less grief.
Like @anatech says, best not done by somebody who has basic experience.
Your choices are:
What do you want it for? Sentiment? Then get it fixed., by a trained person, or gut it out, change the innards.
Unnecessary? Give it away, sold or gifted.
Listen to music? Buy a nice used Japanese set, Denon / Yamaha / Onkyo are to be avoided, complex, trouble prone at times.
No ties to any names above, just being helpful.
Their main market was UK, a little in USA, but the Japanese sets killed them their on sheer quality and price.
A member here, ex Akai tech, ex-moderator, says he has rarely seen such poor quality, and named Bluesound as well in that category.
They are tricky, and tend to be race car like, need maintenace too often.
Best to build another, better result, less grief.
Like @anatech says, best not done by somebody who has basic experience.
Your choices are:
What do you want it for? Sentiment? Then get it fixed., by a trained person, or gut it out, change the innards.
Unnecessary? Give it away, sold or gifted.
Listen to music? Buy a nice used Japanese set, Denon / Yamaha / Onkyo are to be avoided, complex, trouble prone at times.
No ties to any names above, just being helpful.
Hi Alfieh,
I should add that the values on the schematics sometimes differ greatly from what was installed at the factory. If it is an original factory build (not modified or recapped), install what you found in it as far as capacitance is concerned.
If the unit is building DC offset. You may have high current draw or oscillation building up. You have to monitor current draw.
To repair audio amplifiers (or anything) you need a couple basic instruments beyond a cheap meter, soldering iron and desire. You need a good multimeter, the lowest scale should show at least a couple decimals in mV. Otherwise you can't even set bias current properly, or adjust DC offset with any certainty. Some meters react to high frequencies differently on the DC range, and the AC ranges may only be good to 400 Hz. You absolutely do need an oscilloscope and I'll strongly recommend an analogue, dual trace unit. Bare minimum.
You can't hear anything but gross distortion on the test bench. You really do need a distortion meter of some kind. Audio analysers are better but expensive as sin. Remember that passing audio doesn't mean "properly repaired" by any stretch of the imagination. An oscilloscope will not show less than severe distortion.
Several capacitors you showed appear to be open. They will cause all kinds of trouble.
I should add that the values on the schematics sometimes differ greatly from what was installed at the factory. If it is an original factory build (not modified or recapped), install what you found in it as far as capacitance is concerned.
If the unit is building DC offset. You may have high current draw or oscillation building up. You have to monitor current draw.
To repair audio amplifiers (or anything) you need a couple basic instruments beyond a cheap meter, soldering iron and desire. You need a good multimeter, the lowest scale should show at least a couple decimals in mV. Otherwise you can't even set bias current properly, or adjust DC offset with any certainty. Some meters react to high frequencies differently on the DC range, and the AC ranges may only be good to 400 Hz. You absolutely do need an oscilloscope and I'll strongly recommend an analogue, dual trace unit. Bare minimum.
You can't hear anything but gross distortion on the test bench. You really do need a distortion meter of some kind. Audio analysers are better but expensive as sin. Remember that passing audio doesn't mean "properly repaired" by any stretch of the imagination. An oscilloscope will not show less than severe distortion.
Several capacitors you showed appear to be open. They will cause all kinds of trouble.
Of course, you can always build one, if you need to play music, that is always a very good satisfaction inducing thing to do, gives you a sense of pride when listening.
Thanks for all the tips they're quite helpful. I'm mostly repairing it as I wanted to gain some experience. I have a tiny bit, but that's only minor, and in games, electronics like repairing stick drift, etc. I don't really need it for listening as the same family member gave me an old Arcam Alpha 5 they had and atm I'm quite happy with that (I'm a broke uni student ill take any hand me downs I can get) as for the actual steps of repairing ill try desoldering some of the egregious capacitors and test them off the board and see what the voltage and capacitance thankfully the multimeter I own is a pretty good one, unfortunately, I don't own an oscilloscope which maybe something ill has to look into getting
Well, amplifiers are actually not simple things. On the surface they seem to be, but I find most technicians don't really understand how they work.
You need to use an oscilloscope. It is the only real way to tell if it is oscillating or has bursts of RF on waveforms (like the one I'm working on right now).
So all I'm going to say is this. Do it properly. Free to you is no excuse to do anything incorrectly. You learn nothing if you don't complete it or it burns out later. I don't think you're ready for much more than swapping parts (hopefully you get the correct types). If you do get it running, have it checked out by a real audio tech with real equipment. Then you may learn something.
I get stuff in that is actually really good stuff that people have had a "friend" or co-worker take a stab at first. This usually causes damage and almost always increases repair cost. Always a shame. Worse yet, a self styled "technician" gets in there causing trouble and charging a lot. I get people saying "I already spent $xxx on this, I'll only spend $xx more. Well that is unreasonable for starters, and real techs had nothing to do with the botch job. I just completed an expensive amplifier for someone. To repair the damage caused and fix the actual fault was about 70% of what the other guy charged to wreck it. It would have been far less had it come straight on.
The best things to learn on are things you have an understanding on. Have help to assist. Reaching way above your head is really a waste of time, hold onto it until you know more would be my suggestion.
You need to use an oscilloscope. It is the only real way to tell if it is oscillating or has bursts of RF on waveforms (like the one I'm working on right now).
So all I'm going to say is this. Do it properly. Free to you is no excuse to do anything incorrectly. You learn nothing if you don't complete it or it burns out later. I don't think you're ready for much more than swapping parts (hopefully you get the correct types). If you do get it running, have it checked out by a real audio tech with real equipment. Then you may learn something.
I get stuff in that is actually really good stuff that people have had a "friend" or co-worker take a stab at first. This usually causes damage and almost always increases repair cost. Always a shame. Worse yet, a self styled "technician" gets in there causing trouble and charging a lot. I get people saying "I already spent $xxx on this, I'll only spend $xx more. Well that is unreasonable for starters, and real techs had nothing to do with the botch job. I just completed an expensive amplifier for someone. To repair the damage caused and fix the actual fault was about 70% of what the other guy charged to wreck it. It would have been far less had it come straight on.
The best things to learn on are things you have an understanding on. Have help to assist. Reaching way above your head is really a waste of time, hold onto it until you know more would be my suggestion.
Poor man solution:
Sell it, buy a 1943/5200 pair plate amp with the money, or a 3886 if so inclined.
In my opinion, the 2030 and 1875 put out enough power for most home use, unless you like body thumping loud.
Speakers, with them out of fashion, buds are the 'in' thing now, should get almost as scrap.
Input? FM module.
In fact we get the FM radios with built in amp, aux inputs, USB, SD Card, Bluetooth and so on for less than 10 GBP, sound is clear enough.
The FM radios come with either 6283 chips for the mono versions, $6 and up, or stereo, with 4440 chips, $10 and up.
I think that will be a lot less expensive in time and parts than fixing what is frankly a piece of junk when it left the factory.
And over smart circuitry which needs an experienced technician, who has had access to the service bulletins to actually identify the problem.And the right equipment.
Also: some of the parts are simply not available...I had a friend junk a PLC because a small 8 pin chip failed, only source was a pull in the USA.
That cost him nearly $2,000, and a week of lost production.
And that is quite likely, you will end up having to search parts and try them, some sources are dubious.
I say finish your studies, start earning, then take time out for this.
Until then, either store it until you are confident of fixing it, or get rid of it.
You can use the case, transformer and so on, that is also an option.
Sell it, buy a 1943/5200 pair plate amp with the money, or a 3886 if so inclined.
In my opinion, the 2030 and 1875 put out enough power for most home use, unless you like body thumping loud.
Speakers, with them out of fashion, buds are the 'in' thing now, should get almost as scrap.
Input? FM module.
In fact we get the FM radios with built in amp, aux inputs, USB, SD Card, Bluetooth and so on for less than 10 GBP, sound is clear enough.
The FM radios come with either 6283 chips for the mono versions, $6 and up, or stereo, with 4440 chips, $10 and up.
I think that will be a lot less expensive in time and parts than fixing what is frankly a piece of junk when it left the factory.
And over smart circuitry which needs an experienced technician, who has had access to the service bulletins to actually identify the problem.And the right equipment.
Also: some of the parts are simply not available...I had a friend junk a PLC because a small 8 pin chip failed, only source was a pull in the USA.
That cost him nearly $2,000, and a week of lost production.
And that is quite likely, you will end up having to search parts and try them, some sources are dubious.
I say finish your studies, start earning, then take time out for this.
Until then, either store it until you are confident of fixing it, or get rid of it.
You can use the case, transformer and so on, that is also an option.
The Nad 320BEE is not that old you guys are probably confusing it with the 3020 that was a nightmare to repair.
NAD was actual pretty good back in the day but since it was taken over by the Chinese consortium it was only downhill from there.
If the caps are that bad (from your first post) replace them all and pay special attention to the cap and diode on the protection board they are know to cause trouble.
Good luck
NAD was actual pretty good back in the day but since it was taken over by the Chinese consortium it was only downhill from there.
If the caps are that bad (from your first post) replace them all and pay special attention to the cap and diode on the protection board they are know to cause trouble.
Good luck
Nad was never 'junk' just made to a budget, they have made some very good amps over the years.They may not have always been the best constructed, but some of them sound alot better than some amps 3 times the price.
That may be I guess. We had different equipment over here.
I'll never forget seeing 2N3055 on heat sinks designed for plastic packages, very old design techniques back then. Breakers for output protection that went bad. They really didn't sound as good as the average kit here and were sold as "sounding good for the money". Other British equipment was far better. Cyrus for sure.
NAD was never looked upon as being good by industry folks over here. They were very inexpensive compared with most other equipment.
I'll never forget seeing 2N3055 on heat sinks designed for plastic packages, very old design techniques back then. Breakers for output protection that went bad. They really didn't sound as good as the average kit here and were sold as "sounding good for the money". Other British equipment was far better. Cyrus for sure.
NAD was never looked upon as being good by industry folks over here. They were very inexpensive compared with most other equipment.
Mine worked for 20+ years being on for 8 hours a day but it was running hot with poor ventilation. I'm surprised it lasted so long.
I'm very glad for you. I am being honest.
I have one here that isn't worth repair. It blew it's filter caps, known problem that should never happen. A design and component quality issue. I have a bunch of other units, just cheap in every way. On average I would recommend people avoid these products, but if you have one you like, that's really good.
I have one here that isn't worth repair. It blew it's filter caps, known problem that should never happen. A design and component quality issue. I have a bunch of other units, just cheap in every way. On average I would recommend people avoid these products, but if you have one you like, that's really good.