No Sound from NAD 7240PE

ramair02

New Member
Hi all,

I'm a total novice with this stuff, so the help is much appreciated.

I have a NAD 7240PE from the 80's that was my father's. I commandeered it to set up with a new U-Turn turntable and new Pioneer BS22 speakers. The amp has been in my parent's basement for the last 10 years, but worked fine prior.

I got everything hooked up last night, turned on everything, but... no sound. No static from the Tuner, no hissing or buzz, and no sound from the Phono input. The amp powers up and shows the radio station on the display, but for some reason isn't working.

I've been trying to read and research online and it seems a lot of people have fixed these amps fairly easily. I just don't know where to start. I read about the four fuses, so I'll check those today, but what else can I identify visually? And how can I get this thing running again?

Here's a pic of the back, as well as a pic of how it's hooked up: https://imgur.com/gallery/OZx2l

Thanks, all.
 
Firstly, get a copy of the service manual from hifiengine. You need to register (to prevent robot attacks) it is safe
No mention of your skill level and tools available.
Do you have a digital multimeter?
Are you comfortable taking voltage measurements with the amp "live"/powered up?


The amp has joining links at the rear that allow you to separate it into the preamp stage and the power stage.
This allows you to use other pre and power stages. Do you have other equipment with similiar links or a
seperate pre or power amp. By running tests you can isolate the problem as being in pre or power stage.

Many reasons for no sound. Since both channels are affected the power supply would be a good starting point.
As a guess I would say the power supply to the preamp is down. Can you measure the dc voltage at R311 and 312
as shown in the pic, either leg is fine

You should also visually check for any leaking capacitors, NAD has bad history in this area.

Capture.JPG
 
Sorry for not providing some explanation of my skill level. I'm fairly technically inclined and build my own computers, root my phone's, etc. But I'm brand new to being an audiophile and have no knowledge of vintage stereo equipment. I did download the service manual, but have limited ability to understand it. I also don't have a multimeter.

I haven't tried headphones, since I don't have a pair or adapter for the larger plug.

Here's a few pics of the internals. I don't know if it's helpful.

NAD 7240PE Internals https://imgur.com/gallery/0KxD0
 
I have one of these, bought new in 1987, I think. It is very common for them to develop a bit of oxidation/mild corrosion on the switches and other controls, esp. when not used for a while.

I'd try this first: Turn it off, and start exercising the switches, especially the speaker selector, volume AND balance controls, and source switch, as these seem to be the worst culprits. Work them many times, back and forth. But don't neglect the other buttons. Once you have given them a good work out (I'd say 10 mins total effort), turn it on again, and if you don't get sound, try working them all a bit to see if you get any static, etc. Any noises are a good sign that things are working, just dirty contacts, and you will need to follow up with a good contact cleaner, and perhaps some deoxit.

Your unit is exceptionally clean inside, also a good sign.

Edit: also check the Tape Monitor switch for correct position; if it is engaged, you will get nothing unless you have a source connected to the Tape inputs. And also make sure that those Pre-out/Main-in jumpers in the rear panel that mbz mentioned above are installed, as that will also cut all sound if not there.
 
Last edited:
From the internal pics, there looks as though there has been some work on the transistors on the heat sink.
The application of white thermal paste does not appear to be factory standard.
No immediate danger from the caps exploding, you probably have 3-6 months, the amp should be
recapped if you intend to keep, a nice diy project.

Appears to be some history with those heat sink transistors (both channels), this may cause the no
sound problem.

At this stage I'm guessing the problem is with the preamp power supply, since both channels are affected.
A second guess would be some of those transistors on the heat sink have failed, multiple failures since
both channels affected. I would need measurements to go further ie, preamp voltage supply and testing
of those transistors, initially in-circuit would be fine.

Perhaps someone with first hand 7240pe experiance/knowledge can assist.
 
From the internal pics, there looks as though there has been some work on the transistors on the heat sink.
The application of white thermal paste does not appear to be factory standard.
No immediate danger from the caps exploding, you probably have 3-6 months, the amp should be
recapped if you intend to keep, a nice diy project.

Appears to be some history with those heat sink transistors (both channels), this may cause the no
sound problem.

At this stage I'm guessing the problem is with the preamp power supply, since both channels are affected.
A second guess would be some of those transistors on the heat sink have failed, multiple failures since
both channels affected. I would need measurements to go further ie, preamp voltage supply and testing
of those transistors, initially in-circuit would be fine.

Perhaps someone with first hand 7240pe experiance/knowledge can assist.

I think you're right that this has had some work done to it. My dad was telling me that he had an issue with it shortly after purchase and sent it to NAD in Boston. They fixed it up and sent it back. I'm not sure what the issue was.

What is the best way for me to test preamp power supply / transistors on the heat sink? I'm guessing that, since I have very limited knowledge here, I should take it to an electronics repair store. Any suggestions for Manhattan?
 
I have one of these, bought new in 1987, I think. It is very common for them to develop a bit of oxidation/mild corrosion on the switches and other controls, esp. when not used for a while.

I'd try this first: Turn it off, and start exercising the switches, especially the speaker selector, volume AND balance controls, and source switch, as these seem to be the worst culprits. Work them many times, back and forth. But don't neglect the other buttons. Once you have given them a good work out (I'd say 10 mins total effort), turn it on again, and if you don't get sound, try working them all a bit to see if you get any static, etc. Any noises are a good sign that things are working, just dirty contacts, and you will need to follow up with a good contact cleaner, and perhaps some deoxit.

Your unit is exceptionally clean inside, also a good sign.

Edit: also check the Tape Monitor switch for correct position; if it is engaged, you will get nothing unless you have a source connected to the Tape inputs. And also make sure that those Pre-out/Main-in jumpers in the rear panel that mbz mentioned above are installed, as that will also cut all sound if not there.

I will play around with the switches to see if that helps at all and report back. That would be amazing if it's an easy fix like that!

The tape monitor is disengaged. And the pre-out/main-in jumpers are installed.

I'm not familiar with cleaning these devices with contact cleaner and/or deoxit. Are there any good walkthroughs?
 
What is the best way for me to test preamp power supply / transistors on the heat sink? I'm guessing that, since I have very limited knowledge here, I should take it to an electronics repair store. Any suggestions for Manhattan?
Depends what you want to do with the amp and your mix of skill level and any interest in diy.
If the amp has sentimental values and you have no diy interest/skills, send it for repairs, the bill will be more than the amp is worth.
After repairs the amp would still need a recap $100+ depending if diy
If the amp has no sentimental value and you have no diy interest/skills then sell it as is ($20- maybe)
If you want to learn/develop/have some fun then diy, however would need to buy tools.

A basic multimeter (resistance, ac/dc voltage, diode checker...) is required to test the power supply and the transistors.
I would guess $20-$40). Maybe borrow one from a collegue...
 
You can see this: http://audiokarma.org/forums/index.php?threads/the-idiots-guide-to-using-deoxit-revisited.207005/

Deoxit is available at Amazon, etc., but for the time being, plain contact cleaner will get you going, and the CRC product is available at Home Depot for sure, and probably Walmart as well (most likely in their automotive area or close to it).

The volume and balance pots (metal and brown plastic, shaped like a small cylinder) are right behind the front panel, and visible on the lower right of one of your internal shots, and you just squirt them while rotating (unit OFF). The source select travels toward the rear on a long metal shaft (visible to the right of the heat sink), and you would squirt the small switch at the far end. The body of the speaker switch is located just behind its front panel location.
 
Depends what you want to do with the amp and your mix of skill level and any interest in diy.
If the amp has sentimental values and you have no diy interest/skills, send it for repairs, the bill will be more than the amp is worth.
After repairs the amp would still need a recap $100+ depending if diy
If the amp has no sentimental value and you have no diy interest/skills then sell it as is ($20- maybe)
If you want to learn/develop/have some fun then diy, however would need to buy tools.

A basic multimeter (resistance, ac/dc voltage, diode checker...) is required to test the power supply and the transistors.
I would guess $20-$40). Maybe borrow one from a collegue...

Thanks for this. I have a lot of hobbies and am pretty handy overall (grew up working on cars, building computers, handy work around the house, etc.), so I feel confident I can pick this up fairly quickly with some good instructions. I'd love to be able to fix myself, just don't have much experience with electronics

Why would the amp definitely need a recap? Is it unsafe otherwise? Any resources for me to learn would be greatly appreciated. And I can definitely pick up some tools!
 
You can see this: http://audiokarma.org/forums/index.php?threads/the-idiots-guide-to-using-deoxit-revisited.207005/

Deoxit is available at Amazon, etc., but for the time being, plain contact cleaner will get you going, and the CRC product is available at Home Depot for sure, and probably Walmart as well (most likely in their automotive area or close to it).

The volume and balance pots (metal and brown plastic, shaped like a small cylinder) are right behind the front panel, and visible on the lower right of one of your internal shots, and you just squirt them while rotating (unit OFF). The source select travels toward the rear on a long metal shaft (visible to the right of the heat sink), and you would squirt the small switch at the far end. The body of the speaker switch is located just behind its front panel location.

Thanks for the link. That's great and I'll pick up some contact cleaner to start cleaning everything up.

EDIT: Just ordered the DeOxit Audio Survival Kit on Amazon
 
Last edited:
Deoxit is great stuff. Just realize it also contains a lubricant/oil in it that remains after it dries, so you want to avoid spraying it around indiscriminately. Regular contact cleaner does not contain any residue that remains once it evaporates off, and is plastic safe, so it can be used very liberally; it is good for dirty switches, etc., but will not cut through oxidation anywhere as well as deoxit.

On the caps, you will find lots of divergence of opinions here. All agree that electrolytic caps can go bad with age, and probably were not manufactured with the idea of lasting 30-40 years, but whether a particular cap has gone bad over that time has to be determined; many will be fine, but some will not. In general a failing cap isn't unsafe, but some have been known to explode, so it is hard to give absolutes. For a working unit, some experience significant sound improvements following a recap, whereas others don't; I think all can agree that each of these experiences is possible, even discounting some level of subjectivity, as old caps can vary from still good, deteriorated in some way, to failed. Some will choose to recap because they feel it is time and want the unit to sound its best and last another few decades and don't want to worry about the caps, whereas others will undertake it only if they feel something is missing or wrong with the sound they are getting. Personally I have found recapping speaker crossovers to be useful, but less so in amps/tuners, save an obviously failed one in a NAD7220PE, which produced a hum.

mbz is correct in pointing out that you should visually inspect the electrolytic caps for leakage or other issues. NAD, like many companies, used glue under the larger caps to hold them on the board during automated soldering, so don't mistake that for leakage (usually brownish blobs, often partly up the walls). Other clues are bulged tops. In looking at your photos, of the four large black caps (smoothers for the power supply), the one on the lower right looked, in one photo, as if it might possibly have a broad bulge on the top (may have just been the lighting), so check that and the others out. An aural clue to failing power supply caps like those large black ones is a bad hum, but you don't have sound yet. My suggestion is, barring an obviously failed one, to wait on deciding about caps until you at least get sound.
 
Deoxit is great stuff. Just realize it also contains a lubricant/oil in it that remains after it dries, so you want to avoid spraying it around indiscriminately. Regular contact cleaner does not contain any residue that remains once it evaporates off, and is plastic safe, so it can be used very liberally; it is good for dirty switches, etc., but will not cut through oxidation anywhere as well as deoxit.

On the caps, you will find lots of divergence of opinions here. All agree that electrolytic caps can go bad with age, and probably were not manufactured with the idea of lasting 30-40 years, but whether a particular cap has gone bad over that time has to be determined; many will be fine, but some will not. In general a failing cap isn't unsafe, but some have been known to explode, so it is hard to give absolutes. For a working unit, some experience significant sound improvements following a recap, whereas others don't; I think all can agree that each of these experiences is possible, even discounting some level of subjectivity, as old caps can vary from still good, deteriorated in some way, to failed. Some will choose to recap because they feel it is time and want the unit to sound its best and last another few decades and don't want to worry about the caps, whereas others will undertake it only if they feel something is missing or wrong with the sound they are getting. Personally I have found recapping speaker crossovers to be useful, but less so in amps/tuners, save an obviously failed one in a NAD7220PE, which produced a hum.

mbz is correct in pointing out that you should visually inspect the electrolytic caps for leakage or other issues. NAD, like many companies, used glue under the larger caps to hold them on the board during automated soldering, so don't mistake that for leakage (usually brownish blobs, often partly up the walls). Other clues are bulged tops. In looking at your photos, of the four large black caps (smoothers for the power supply), the one on the lower right looked, in one photo, as if it might possibly have a broad bulge on the top (may have just been the lighting), so check that and the others out. An aural clue to failing power supply caps like those large black ones is a bad hum, but you don't have sound yet. My suggestion is, barring an obviously failed one, to wait on deciding about caps until you at least get sound.

Ok, great and thanks for the insight.

Here's where I'm at...

I picked up some Contact Cleaner while I wait for the DeOxit kit to arrive. I couldn't find the CRC, but found Gunk Electric Motor Contact Cleaner.

I've cleaned the Speaker switch (A, B, Off, A&B) and the CD/Phono/Tuner/Video switch and ran them back and forth about 40x each while still wet with the cleaner.

I noticed some oxidation on the Phono inputs inside the amp. There is green corrosion/oxidation circling the inside of the Phono inputs, so I put contact cleaner on a q-tip and tried to get as much off as possible. There is still some green, but it's a lot better. But since I don't have sound from any of the inputs, I doubt this is the issue.

The four big black caps are actually all flat on top and there is no leakage around the base of any of those caps. They look to be in good shape, visually.

In general, the internals of the whole amp are pretty dusty. Can I liberally spray the contact cleaner across the whole board, or is that a bad move. Also, I have a can of rubbing alcohol spray that I could use instead. Would that be advised?

I'm letting it dry now and will hook it up again soon to test if I can get any sound out of the amp.

EDIT: Here are some pics of the Phono oxidation (after cleaning with contact cleaner) and a better shot of the caps - https://imgur.com/gallery/dbU8O

EDIT2: Hooked everything up. Still no sound. If anything, I should be able to get static or something from the Tuner, right? The speakers remain dead silent on Tuner with volume turned up, Tape Monitor unpressed and seeking through stations.
 
Last edited:
I'm not familiar with the Gunk version, but if it evaporates off cleanly, it should be fine.

That is a surprising amount of green oxidation on the phono inputs, and also odd that only on that one. I've not seem that much on any of my gear, and I would suspect some moisture got to that corner of the unit at some point. Given that, I would not trust using a phono signal to test things right now. Radio signal through to the tuner is more reliable, although the two switches on the front panel that control AM-FM and Search can go intermittent (mine did) and might interfere with the signal. The remedy is to use contact cleaner on the switches, which are located toward the middle of the interior, at the far ends of the two dog-legged white plastic arms; just spray in those switches while engaging/unengaging the front panel buttons several times. After this, if the receiver can reliably auto-tune to known strong local stations and show a stereo signal, it should be ok to use for testing purposes via selecting tuner on the input selector, but I would not rely on the presence of inter-station hiss, iif that is what you are doing. Bottom line: If you have any doubts, it would be better to hook up a CD or DVD player known to be working and play CDs for the input source.

When you have a reliable source putting out a signal, turn up the volume to 9 or 10 o'clock, and then try operating all other controls (including that balance knob inside the volume knob). That can be fully switching the the controls back and forth, as well as just rocking them about their detent positions. If you get no sounds whatsoever from that, you have some other significant problem. But I would first double check those fuses, though, because you are relying on a visual for that (you don't have a meter), and the filament is pretty small and it is easy to miss a break; best to pull each fuse out so you can check it carefully under bright light, and the act of removing and installing them will refresh their contacts. You can hit those contacts with contact cleaner too.

Beyond these things, as mbz suggested above, there is only a limited number of things you can do without the help of a meter. Pulling the Pre-out-Main-in jumpers and trying to feed signal from another working device to the amp (via Main-In), or signal from the Pre-out to another device, would help to start isolating the problem.

As for the dust, most of the time it isn't too important as long as it is not piled up in places; in a humid environment, it could start to cause issues. Mine is dustier than yours, and plays fine. It is best to vacuum or blow out whatever you can. If you want you can then swab things with dry tissue or q-tips, etc. at first, and then wetted with contact cleaner. I would avoid alcohol: rubbing alcohol has other things in it (oils, etc.) and most other consumer alcohols have a few percent to several percent water in them, which can remain for quite a while after the alcohol evaporates.
 
Ok, we've got some progress!!! So I'm super excited, but kind of bummed at the same time.

I just cleaned everything again and let it dry. Now I'm getting audio from the Tuner (both AM & FM) through the speakers, as well as hearing my turntable through the Phono inputs.

The problem now is that I have to turn the volume up ALL THE WAY to get a very low sound out of the speakers (both on Tuner & Phono). And it's making really loud pops. What's next?

Edit: Ok, I think it just needed to warm up. After a couple of minutes of barely audible audio through my turntable, the volume kicked up...and it sounds pretty good! I'm incredibly surprised this worked and so so so so happy. Seriously, thank you for your help (northpaw especially!)
 
There's definitely a buzz in between songs that's audible, so I'm sure there is more I can do to make my setup perfect, but I'm just so happy that the amp is working at all! I was really pumped when I found the NAD at my parents house and then very disappointed when I thought I was going to have to go another route.
 
It sounds like you had some residual moisture that needed to dry out. Not recommended to dry it out under power (try a hair dryer next time, or wait overnight).

As for any remaining clicks, pops, and even if the volume remains low, you probably still have residual dirt/oxidation on some contacts, and treating with deoxit when you get it will help. Also, with the unit off, pull out those Pre-to-Main jumpers and polish them up a bit, and apply contact cleaner in the jacks with a q-tip like you did for some other jacks. Troublesome transistors can also create pops, but most times the unit will not continue to work very long if that is the case.

As for "buzz", if only on phono, make sure your ground wire from the turntable is attached to the receiver, and if it is, make sure the ground connection on your cartridge is good and done correctly (some have jumpers on the cartridge pins and must be set appropriately). If only on radio, does it go away or lessen if you go to mono? if so, worry about your antenna positioning. If on everything (you should check with a CD or an ipod, etc), it could be hum from a degraded power supply cap, etc. One half-assed test you can try for that is while the unit is playing with the cover off, lightly place your index finger on top one of the large black caps and very gently nudge it in all directions, and see if it has any effect. Try each of those 4 caps, one at a time. Any response indicates a problem with that cap or its solder joints; absence of a response does not insure that cap is ok, though.

Anyway, glad you are getting functionality. Disuse of this kind of equipment is the 2nd worst thing for it; the worst is, of course, abuse.
 
It sounds like you had some residual moisture that needed to dry out. Not recommended to dry it out under power (try a hair dryer next time, or wait overnight).

As for any remaining clicks, pops, and even if the volume remains low, you probably still have residual dirt/oxidation on some contacts, and treating with deoxit when you get it will help. Also, with the unit off, pull out those Pre-to-Main jumpers and polish them up a bit, and apply contact cleaner in the jacks with a q-tip like you did for some other jacks. Troublesome transistors can also create pops, but most times the unit will not continue to work very long if that is the case.

As for "buzz", if only on phono, make sure your ground wire from the turntable is attached to the receiver, and if it is, make sure the ground connection on your cartridge is good and done correctly (some have jumpers on the cartridge pins and must be set appropriately). If only on radio, does it go away or lessen if you go to mono? if so, worry about your antenna positioning. If on everything (you should check with a CD or an ipod, etc), it could be hum from a degraded power supply cap, etc. One half-assed test you can try for that is while the unit is playing with the cover off, lightly place your index finger on top one of the large black caps and very gently nudge it in all directions, and see if it has any effect. Try each of those 4 caps, one at a time. Any response indicates a problem with that cap or its solder joints; absence of a response does not insure that cap is ok, though.

Anyway, glad you are getting functionality. Disuse of this kind of equipment is the 2nd worst thing for it; the worst is, of course, abuse.

Ah, good to know about the residual moisture. I won't make that mistake again. Appreciate the heads up.

I'm definitely going to go over everything I did today again when the DeOxit comes in. And I'll clean up the jumpers too. I bought some pipe cleaners too, so that I can get inside all of the RCA plugs across the back panel. I couldn't get in there with a q-tip.

The U-Turn Orbit (my turntable) actually doesn't have a ground wire. I know that's odd, but from reviews it sounds like they did a really good job of grounding the unit and not making that necessary. The buzz does only seem to be on Phono, although I don't have very good radio reception, so it's tough to tell. I'll get a 3.5mm to RCA cable, or something, so I can test playing audio from my phone. And I'll give the "half-assed" test a shot.

Again. thanks so much for the help.
 
Simple test: just set the input selector to CD (with nothing connected to the CD jacks on the rear panel) and start turning up the volume. If no or much less buzz or hum, your power supply is ok, and your cartridge/turntable is the source.

I'm not familiar with your turntable and the lack of ground, but it sounds like a potential problem to me. The phono section of the receiver has much higher gain than the other inputs, making it more susceptible to buzz or hum. You may also have a ground loop; best way to help avoid that is to make sure the receiver and turntable are plugged into the same outlet. If the turntable has a 2-prong AC plug that is not polarized, you can try flipping that to see if you get more or less buzz one way over the other.

Another simple test: turn the input selector to something other than phono, disconnect the turntable RCAs from the back panel of the receiver (never connect or disconnect inputs while the receiver is powered on and those inputs are selected), and then set the input selector back to phono and start turning up the volume. If you hear less buzz at a given volume level that way, I'd be suspicious it is a ground problem from the cartridge.

I think you will find the 3.5mm to RCA cable a good investment. You can play internet radio into the receiver that way as well. Another way is way ChromeCast Audio if you have an android device or chromebook handy, where the stream is set up from your wifi router to the CCA; I really like this way because as once you set up the stream, you can turn your device off and the streaming continues.
 
Back
Top Bottom