First attempt at amp repair

[2341]

I've recently had trouble starting up my NAD 314. Knowing a bit about electronics but nothing about amps, I'd like to have a go at repairing it. When I hit the power on button, usually a red LED comes on. After a few seconds, there is a "click" and the LED goes from red to green. Recently, after powering on, the LED came on red as usual and there was the usual click but the LED did not go green and the click repeated every second or so. I've had the case off and identified the clicking as coming from a relay located by the speaker outputs. A little Googling leads me to believe that this is the "speaker relay"? I've cleaned the dust out with the old air duster and given the circuit board a good eyeballing to see if there are any obviously failed components but I cannot see any. This is to be expected as the amp does occasionally power on correctly after being left unplugged for a while. I was hoping someone could offer some further steps to troubleshoot this? I've had a look around on Google to see if there are any similar problems. There are a few guys complaining about the same thing on the NAD C350, with someone even contributing a YouTube video demonstrating the effect. Is this a common problem with amps/NAD amps?

 

[Haoleb]

The most likely thing that is happening is the protection circuit is sensing something is not right and it is not turning on the speaker protection relay. Rather than say, a bad relay coil. This relay is in place to disconnect the output of the amplifier in the event that something happens that will damage the amplifier or speakers.

Your first task will be to find a schematic.. And the first place i would look is to check the DC offset of the amplifier. Since the speaker relay will not engage you will have to check it before the relay. I wont go into too much detail but if you cant figure it out this may be beyond your scope.

 

[highfigh]

I've recently had trouble starting up my NAD 314. Knowing a bit about electronics but nothing about amps, I'd like to have a go at repairing it. When I hit the power on button, usually a red LED comes on. After a few seconds, there is a "click" and the LED goes from red to green. Recently, after powering on, the LED came on red as usual and there was the usual click but the LED did not go green and the click repeated every second or so. I've had the case off and identified the clicking as coming from a relay located by the speaker outputs. A little Googling leads me to believe that this is the "speaker relay"? I've cleaned the dust out with the old air duster and given the circuit board a good eyeballing to see if there are any obviously failed components but I cannot see any. This is to be expected as the amp does occasionally power on correctly after being left unplugged for a while. I was hoping someone could offer some further steps to troubleshoot this? I've had a look around on Google to see if there are any similar problems. There are a few guys complaining about the same thing on the NAD C350, with someone even contributing a YouTube video demonstrating the effect. Is this a common problem with amps/NAD amps?

Disconnect the speaker wires from the amp- if the light goes green, check the wires for damage. Do you have a cat or dog? They sometimes like to chew on wires.

 

[Alex2507]

I've been down this road so let's just start talking about what your budget is for a new amp.

 

[TLS Guy]

The most likely thing that is happening is the protection circuit is sensing something is not right and it is not turning on the speaker protection relay. Rather than say, a bad relay coil. This relay is in place to disconnect the output of the amplifier in the event that something happens that will damage the amplifier or speakers.

Your first task will be to find a schematic.. And the first place i would look is to check the DC offset of the amplifier. Since the speaker relay will not engage you will have to check it before the relay. I wont go into too much detail but if you cant figure it out this may be beyond your scope.

Yes, the relay is doing it's job. Check you wiring. If the unit does this with no speakers connected then there is an amp with a failed output stage, that is causing the DC rail voltage to appear at the speaker terminals. If the relay did not do its job, then your woofers would literally smoke and catch fire.

You need a service manual, FET or tube VOM, scope and signal generator.

NAD = Not Always Dependable.

After checking, I find I have a service manual for that unit in pdf. on file, but it is too big to upload.

You can download it from the HiFi engine. I have worked on those before, and they are a real misery unit. It is a 35 watt per channel integrated. I suspect you are in the UK as they were aimed at this market.

If you don't have the equipment to work on it, it is not worth a red cent to have it serviced. I think yours must be just about the last one to have been running. I would bet at least 99% of those are already junked.

 

[Swerd]

I've been down this road so let's just start talking about what your budget is for a new amp.

The OP actually intends to repair his amp as in RIY repair it yourself.

Your efforts did qualify as DIY – dismantle it yourself – followed by – dumpsterize it yourself .

 

[Alex2507]

The OP actually intends to repair his amp as in RIY repair it yourself.

Your efforts did qualify as DIY – dismantle it yourself – followed by – dumpsterize it yourself .

I don't think dumpsterize is a word.

 

[slipperybidness]

The OP actually intends to repair his amp as in RIY repair it yourself.

Your efforts did qualify as DIY – dismantle it yourself – followed by – dumpsterize it yourself .

Don't let these guys discourage you. I think it is a good idea to repair stuff yourself and now you have a good place to start. Be aware that you may have to buy some more tools etc, so it may end up being more of an investment of time and money than you expected. But, if you do fix it, then the experience gained is just as good as the repaired electronic.

Consider this book as a possible starting point:
Amazon.com: How to Diagnose and Fix Everything Electronic eBook: Michael Jay Geier: Kindle Store

 

[TLS Guy]

Don't let these guys discourage you. I think it is a good idea to repair stuff yourself and now you have a good place to start. Be aware that you may have to buy some more tools etc, so it may end up being more of an investment of time and money than you expected. But, if you do fix it, then the experience gained is just as good as the repaired electronic.

Consider this book as a possible starting point:
Amazon.com: How to Diagnose and Fix Everything Electronic eBook: Michael Jay Geier: Kindle Store

I'm not trying to discourage the OP. However he has to have a circuit and understand how it works. It does require equipment. At the minimum a high impedance amplified volt meter, a Variac, a dual channel scope and a signal generator. Obviously heat sinks, desoldering and soldering iron is required, as well as an assortment of the appropriate hand tools.

It is easy to make hings worse. However if he wants to put in the work and purchase what is required then it is a good idea. If he trashes that unit it is no loss, and he will have learned something along the way.

Actually I believe most on these forums who have all but simple minimal systems should invest in the above equipment and learn how to use it.

 

[Haoleb]

It does require equipment. At the minimum a high impedance amplified volt meter, a Variac, a dual channel scope and a signal generator. Obviously heat sinks, desoldering and soldering iron is required, as well as an assortment of the appropriate hand tools.

While it would be great to have all that equipment on hand, most people do not. I personally have repaired tons of stuff from amplifiers, tv's, industrial controllers, etc... with just the use of a DMM and soldering iron.

This is off topic but quite frankly I have been reading your posts for a while and I think your attitude towards telling people what their problem is and what they should do because you are the expert on every subject goes beyond helpful into arrogant at times. Not everybody can afford to do things 100% the right way...so what?

 

[TLS Guy]

While it would be great to have all that equipment on hand, most people do not. I personally have repaired tons of stuff from amplifiers, tv's, industrial controllers, etc... with just the use of a DMM and soldering iron.

This is off topic but quite frankly I have been reading your posts for a while and I think your attitude towards telling people what their problem is and what they should do because you are the expert on every subject goes beyond helpful into arrogant at times. Not everybody can afford to do things 100% the right way...so what?

All I can say is, you are smarter and have better luck than me. Under the star I seem to have been born under, things seem to go wrong and fall apart quickly, unless I do it right.

So be my guest and help the OP fix his amp. You can download the circuit from HiFiengine.

If you can help him with an easy fix, I'm sure he will appreciate it.

 

[BoredSysAdmin]

Don't let these guys discourage you. I think it is a good idea to repair stuff yourself and now you have a good place to start. Be aware that you may have to buy some more tools etc, so it may end up being more of an investment of time and money than you expected. But, if you do fix it, then the experience gained is just as good as the repaired electronic.

Consider this book as a possible starting point:
Amazon.com: How to Diagnose and Fix Everything Electronic eBook: Michael Jay Geier: Kindle Store

Lets say someone does a google search like this one
https://www.google.com/search?hl=en&as_q=McGraw+Hill+How+to+Diagnose+and+Fix+Everything+Electronic&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=&as_occt=any&safe=images&tbs=&as_filetype=pdf&as_rights=

You might want to glance over few pages to see if you like it, but buy it if you like it - I got some background in electronics and the book seems to make sense to me

 

[honeymonster]

I've recently had trouble starting up my NAD 314. Knowing a bit about electronics but nothing about amps, I'd like to have a go at repairing it. When I hit the power on button, usually a red LED comes on. After a few seconds, there is a "click" and the LED goes from red to green. Recently, after powering on, the LED came on red as usual and there was the usual click but the LED did not go green and the click repeated every second or so. I've had the case off and identified the clicking as coming from a relay located by the speaker outputs. A little Googling leads me to believe that this is the "speaker relay"? I've cleaned the dust out with the old air duster and given the circuit board a good eyeballing to see if there are any obviously failed components but I cannot see any. This is to be expected as the amp does occasionally power on correctly after being left unplugged for a while. I was hoping someone could offer some further steps to troubleshoot this? I've had a look around on Google to see if there are any similar problems. There are a few guys complaining about the same thing on the NAD C350, with someone even contributing a YouTube video demonstrating the effect. Is this a common problem with amps/NAD amps?

I would recommend you check your speaker wiring for short circuits.

 

[Alex2507]

This is off topic but quite frankly I have been reading your posts for a while and I think your attitude towards telling people what their problem is and what they should do because you are the expert on every subject goes beyond helpful into arrogant at times.

Oh cool, you're doing evaluations. Can I be next?