Hi all,
I picked up a NAD 314 for little money. The right channel was dead. The first quick examination learned that the pushing (not turning) the bass-control had an effect. It was not tightly connected to the metal case, so I screwed the nut on. Both channels worked now, but after a while it sometimes still fades and becomes then louder again. Strange, because the outside of the bass-control potentiometer should not have influence on the circuit (I suppose). But when I move the metal 'turn-pin' of the potmeter against the metal case you can hear it on the speakers.
So I thought it was a grounding problem and I made sure the outside of the tone-control potontiometer was connected with the grounded case by soldering. This helped away the fading, but now I hear a very loud click when I activate the tone circuit by pressing the tone defeat button.
When I click the button in (bypass tone circuit) I hear nothing, but when I click it again (turn on tone-circuit) I hear a click. The longer I wait, the louder. This makes me think there somewhere is a DC-current which shouldn't be there. But where?
This all makes me think the problem is bigger as I thought. The amp works fine now, great sound also. The fading is almost over, but not at all.
Can somebody help me? What could this problem be? I include the schematic of the line amp part (and tone-control circuit), which I got from Etsang (thanks again).
I have basic experience an knowledge with electronics and amplifiers and I like to learn, so any help would be greatly appreciated.
I picked up a NAD 314 for little money. The right channel was dead. The first quick examination learned that the pushing (not turning) the bass-control had an effect. It was not tightly connected to the metal case, so I screwed the nut on. Both channels worked now, but after a while it sometimes still fades and becomes then louder again. Strange, because the outside of the bass-control potentiometer should not have influence on the circuit (I suppose). But when I move the metal 'turn-pin' of the potmeter against the metal case you can hear it on the speakers.
So I thought it was a grounding problem and I made sure the outside of the tone-control potontiometer was connected with the grounded case by soldering. This helped away the fading, but now I hear a very loud click when I activate the tone circuit by pressing the tone defeat button.
When I click the button in (bypass tone circuit) I hear nothing, but when I click it again (turn on tone-circuit) I hear a click. The longer I wait, the louder. This makes me think there somewhere is a DC-current which shouldn't be there. But where?
This all makes me think the problem is bigger as I thought. The amp works fine now, great sound also. The fading is almost over, but not at all.
Can somebody help me? What could this problem be? I include the schematic of the line amp part (and tone-control circuit), which I got from Etsang (thanks again).
I have basic experience an knowledge with electronics and amplifiers and I like to learn, so any help would be greatly appreciated.
Attachments
looking at the circuit, i can see 2 places where DC leakage could cause the popping you mention. C148 near the line amp output, and the 47uf electrolytic near the tone defeat switch. if either of those caps were leaky, you could get the popping you mention. put a voltmeter at the wiper of the switch and see if you have dc there (switch the tone control in and watch for dc, then switch the controls out and watch for dc) , then check at the junction of r 160 and r170 for dc. it most likely is at the switch. if you find dc at either place replace the cap causing it.
also it sounds like you should rebuild that noisy pot. how to do this is shown here:
http://www.geofex.com/Article_Folders/potsecrets/potscret.htm
also it sounds like you should rebuild that noisy pot. how to do this is shown here:
http://www.geofex.com/Article_Folders/potsecrets/potscret.htm
Thanks for the advice. I think i traced the 'pop'-problem now. It was in the right channel of the pre/line amp. My multimeter couldn't find any DC at the points you told me, but I think that's because it's a digital meter (maybe to slow to catch the pop).
Unfortunately my fade-problem is not solved. Both channels are still fading/cracking/dead sometimes. I disconnected the pre-amplifier from the main-amp and connected a cd-player (with adjustable volume) to the main-amp. Still cracking and fading. Not sure if this is a right method, but I think this isolates the fading-problem to the main-amp. Am I right?
And again my question is, what could be the problem?
Unfortunately my fade-problem is not solved. Both channels are still fading/cracking/dead sometimes. I disconnected the pre-amplifier from the main-amp and connected a cd-player (with adjustable volume) to the main-amp. Still cracking and fading. Not sure if this is a right method, but I think this isolates the fading-problem to the main-amp. Am I right?
And again my question is, what could be the problem?
try checking the collectors on the diff amp (LTP) and see if the voltages are drifting there...... also check the emitters (could be the current source) if you have any zeners in your input stage, replace them. any problems with the diff amp will cause changes in gain. zeners get noisy (so do some diff amp transistors)
I just discovered this thread.
I have had a NAD 314 since new (Nov 97) and in past few years it has been exhibiting symptoms similar to what the OP describes. In my case, the unit would operate fine for about an hour or so till it warmed up, then the left/right channels would fade in and out randomly. If I adjust the volume up or down from the source input (eg TV), not using the volume pot on the amp, the problem temporarily goes away (few seconds). I pretty sure its not a dirty pot problem since I don't get the characterisic crackly sound when I turn any of the pots.
I suspect a bad solder joint/ground or something similar that loosens up when things get warm.
Interesting to read that the OP found that the speaker relays were a major contributing factor. A while back I did a similar test using a source direct into the power amp and found that things were working properly. I suspect my problem is in the preamp.
Anyway, all this to say thanks for sharing your experience, it may help me.
Alan
I have had a NAD 314 since new (Nov 97) and in past few years it has been exhibiting symptoms similar to what the OP describes. In my case, the unit would operate fine for about an hour or so till it warmed up, then the left/right channels would fade in and out randomly. If I adjust the volume up or down from the source input (eg TV), not using the volume pot on the amp, the problem temporarily goes away (few seconds). I pretty sure its not a dirty pot problem since I don't get the characterisic crackly sound when I turn any of the pots.
I suspect a bad solder joint/ground or something similar that loosens up when things get warm.
Interesting to read that the OP found that the speaker relays were a major contributing factor. A while back I did a similar test using a source direct into the power amp and found that things were working properly. I suspect my problem is in the preamp.
Anyway, all this to say thanks for sharing your experience, it may help me.
Alan
Hello,
I discover this threat with a lot of pleasure because I also have a NAD 314 and start to have some similar problem.
Therefor there is a little different, I only have the prob on the right channel. So it shouldn't be coming from the pot...
May someone have an idear to help me ?
I precise that I am not really use to electronic testing and just created a preamp in my life... I am full of good will so with appropriate explainations I will manege the best I can
Thks
Fabrice (from France)
I discover this threat with a lot of pleasure because I also have a NAD 314 and start to have some similar problem.
Therefor there is a little different, I only have the prob on the right channel. So it shouldn't be coming from the pot...
May someone have an idear to help me ?
I precise that I am not really use to electronic testing and just created a preamp in my life... I am full of good will so with appropriate explainations I will manege the best I can
Thks
Fabrice (from France)
fading channels
Hi,I also have a 314 with fading channels.After about 1 hour one channel ,normally the left but sometimes the right channel stops working on quieter parts of the music,working again as the music gets louder.The channel dosent fade but stops working at low volume.The fault is solved temporarily by turning the volume up.It appears to be a component or connection which needs more power flowing through it as it does not happen at higher volumes.Their is also a permanent problem with the power on light.The light output varies from bright to almost off.When the amp is switched on the light is bright but this fades and reapears at random.Sometimes pressing different input buttons affects this.The brightness of the light has no effect on the music fading allthough I suspect they may be linked .Any help would be appreciated.Thanks
Hi,I also have a 314 with fading channels.After about 1 hour one channel ,normally the left but sometimes the right channel stops working on quieter parts of the music,working again as the music gets louder.The channel dosent fade but stops working at low volume.The fault is solved temporarily by turning the volume up.It appears to be a component or connection which needs more power flowing through it as it does not happen at higher volumes.Their is also a permanent problem with the power on light.The light output varies from bright to almost off.When the amp is switched on the light is bright but this fades and reapears at random.Sometimes pressing different input buttons affects this.The brightness of the light has no effect on the music fading allthough I suspect they may be linked .Any help would be appreciated.Thanks
Fading channels,Fading light
Hi,I may have solved the fading light problem by tapping various parts of the circuit board.Tapping close to the centre of the board,quite hard,with a pencil seems to have solved the problem.This may be temporary,only time will tell.
The fading channels are still there,allthough only the right one so far.If juko could give a better description of how he solved the problem this would be appreciated .Thanks
Hi,I may have solved the fading light problem by tapping various parts of the circuit board.Tapping close to the centre of the board,quite hard,with a pencil seems to have solved the problem.This may be temporary,only time will tell.
The fading channels are still there,allthough only the right one so far.If juko could give a better description of how he solved the problem this would be appreciated .Thanks
fading channels,fading light.SORTED!
Hi,thanks to reply from juko my amp is sorted,yippee.The relay is black plastic approx 30x30x10mm,and clicks at switch on and off.To get to the contacts you need to remove the black plastic cover.Using a good light you can see clips at the base.Release these to lift the cover up,a small screwdriver bent to 45 degrees helps.Underneath you will find the contacts.If you switch on, the contacts will close showing where they connect,this is what needs cleaning.Juko used brown paper or card and contact spray(reccomended),I used fine sandpaper,allthough I read somewhere not to do this( I was on a do or die mission).Switch off and place card in the contact gap,carefully close the gap using a small screwdriver and pull the card upwards,continue until you think both contacts are clean.Try the amp,if it works replace the cover and enjoy the music.I think my amp now sounds sharper and tighter(how do you describe sound?)and possibly louder at low volume.Allthough this might just be in my head!.I am a carpenter,not an electroncs repair man so feel free to correct my methods.Thanks again to Juko,you have saved my amp from being attacker with a hammer.I can finally relax and enjoy my music! . Live long and prosper.
Hi,thanks to reply from juko my amp is sorted,yippee.The relay is black plastic approx 30x30x10mm,and clicks at switch on and off.To get to the contacts you need to remove the black plastic cover.Using a good light you can see clips at the base.Release these to lift the cover up,a small screwdriver bent to 45 degrees helps.Underneath you will find the contacts.If you switch on, the contacts will close showing where they connect,this is what needs cleaning.Juko used brown paper or card and contact spray(reccomended),I used fine sandpaper,allthough I read somewhere not to do this( I was on a do or die mission).Switch off and place card in the contact gap,carefully close the gap using a small screwdriver and pull the card upwards,continue until you think both contacts are clean.Try the amp,if it works replace the cover and enjoy the music.I think my amp now sounds sharper and tighter(how do you describe sound?)and possibly louder at low volume.Allthough this might just be in my head!.I am a carpenter,not an electroncs repair man so feel free to correct my methods.Thanks again to Juko,you have saved my amp from being attacker with a hammer.I can finally relax and enjoy my music! . Live long and prosper.
brown paper bag and contact cleaner is what i would recommend. never underestimate the abrasive properties of paper. i've worked on check (checque outside the US) processing equipment and a common failure was the hardened steel paper guides getting grooves cut in them by the checks as they moved across the surface.
before you use any burnishing paste, chec it to make sure it's not conductive, and clean it ALL off, so you don't leave grit behind that can wear out the contacts.
i've also seen burnishing tools made of spring steel with a rough finish on them. these work best in hard-to-reach areas that you can't maneuver the brown paper in.
before you use any burnishing paste, chec it to make sure it's not conductive, and clean it ALL off, so you don't leave grit behind that can wear out the contacts.
i've also seen burnishing tools made of spring steel with a rough finish on them. these work best in hard-to-reach areas that you can't maneuver the brown paper in.
Hi, I orginally posted on this thread back in 2008. Since then my unit has been in storage. I recently pulled it out and re-read this thread along with a similar thread on the NAD 304, a precursor model that exibits exactly the same symptoms. By tapping the speaker relay, I confirmed my fading issue was due to the relay. I tried to remove the relay cover but ended up runining it. I purchased a new relay from Newark electronics
($2 part, $15 shipping) and soldered it in place. The amp is running great now!! The part I ordered for replacement was a PANASONIC JW2ASN-DC24V.
($2 part, $15 shipping) and soldered it in place. The amp is running great now!! The part I ordered for replacement was a PANASONIC JW2ASN-DC24V.
wow ! My NAD314 got same problem - fading
Thanks to this post I've done some cleaning for this particular relay and ... so far so good.
But while cleaning I've noticed that the contacts of one channel are a bit burnt. Not completely but it is noticeable. I'd replace the relay but lets see first - maybe the cleaning helped enough.
Thank you guys for sharing this DIY
Thanks to this post I've done some cleaning for this particular relay and ... so far so good.
But while cleaning I've noticed that the contacts of one channel are a bit burnt. Not completely but it is noticeable. I'd replace the relay but lets see first - maybe the cleaning helped enough.
Thank you guys for sharing this DIY
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