NAD 7400

[Inkstained]

Old guy/new member here - My NAD 7400 has died. It's given great service for a very long time. Am I correct in thinking that it is worth repairing/restoring/rebuilding? Or is this a lost cause? As a retired guy on a limited income, at the very least doing the repair is much more attractive than spending for an equivalent receiver, even if there is such a thing. Any advice or comment will be appreciated.

 

[ski2xblack]

Those were pretty respectable units in their day. To replace it with something equivalent would cost quite a bit. I suspect repair would be less, but that all depends on what needs to be fixed.

Reputable repair shops seem to be going the way of the Dodo, unfortunately, but I can recommend Don at the Sound Doctor with confidence.

The Sound Doctor

Electronic Service Center For over 40 years The Sound Doctor has provided audio repair services in Northern Colorado.

lovelandsounddoctor.com

 

[TLS Guy]

Old guy/new member here - My NAD 7400 has died. It's given great service for a very long time. Am I correct in thinking that it is worth repairing/restoring/rebuilding? Or is this a lost cause? As a retired guy on a limited income, at the very least doing the repair is much more attractive than spending for an equivalent receiver, even if there is such a thing. Any advice or comment will be appreciated.

That unit is potentially repairable if you can find a tech. They have been put out of business as modern gear is not repairable except by board repair if available. It would be risky to get that NAD repaired, as there is a good chance it needs an IC no longer available and you still have to pay the tech for his/her time.

Honestly I never found NAD to be the best built equipment.

Analog AV receivers are now a thing of the past. So you will need to decide if you are going to get into AV. Due to limited demand analog only equipment is costly. AV is more reasonable, but you need to be able to connect it to a TV with HDMI.

 

[Eppie]

Old guy/new member here - My NAD 7400 has died. It's given great service for a very long time. Am I correct in thinking that it is worth repairing/restoring/rebuilding? Or is this a lost cause? As a retired guy on a limited income, at the very least doing the repair is much more attractive than spending for an equivalent receiver, even if there is such a thing. Any advice or comment will be appreciated.

The service manual for the 7400 is available on-line. That is a big bonus for any tech willing to take a look at it. I had a quick scan over the service manual and I think that unit is quite serviceable depending upon what the issue is. Might cost you one or two hours bench labour to get an estimate.

 

[ski2xblack]

repair is much more attractive than spending for an equivalent receiver, even if there is such a thing.

Not really such a thing.

What separated your 7400 from the rest of the pack was the seriously ballsy amp (good luck finding a stereo reciever or AVR that would match it), excellent phono pre, and genuinely useful tone/eq controls.

If you rely on any of those features specifically, repair is probably worth doing. To replicate the tone controls and bass eq (essentially a Linkwitz transform) would put you in AVR or miniDSP territory, as I don't know of any current stereo kit that offers such flexibility. To get similar power would require external amplification.

If you don't use those features or need that much juice, you could go the replacement route. Given the cost of, say, a new 100w Yamaha networking stereo reciever at >$1k, repair may still be the most cost effective way to go.

To @Eppie 's point, Sound Doctor charges $50 nonrefundable diagnostic fee which is applied to repair costs if you decide to have them fix it.

 

[TLS Guy]

The service manual for the 7400 is available on-line. That is a big bonus for any tech willing to take a look at it. I had a quick scan over the service manual and I think that unit is quite serviceable depending upon what the issue is. Might cost you one or two hours bench labour to get an estimate.

Download not recommended from that site. Last time I used an Eastern European site I got hacked from Russia. Stay away from those. I will see if there is a manual on Hi-Fi Engine later. I have worked on NAD gear before and got negative impressions. I guess I am spoilt with Quad.

If the OP wants old analog gear, then he should look at Quad gear on eBay. He will have to have separates as Peter Walker was dead set against receivers of all stripes.

 

[Eppie]

Don't use Chrome or Edge and stick with a safe browser. I use Firefox with AdBlocker and have never been hacked. Electrotanya is still the most popular site for service manuals but you may have to turn off your ad blocker for the Captcha to work and to get the download link. That's probably the biggest risk as the hack will come from an ad and not the main site. The manual is only 5MB so anyone can PM me if they would like the PDF emailed. It's a very complete manual with alignment instructions for the pre-amp and FM tuner and even has schematics for the remote.

 

[Inkstained]

Thanks very much for your replies, everyone. I think that I will have it repaired. A specialist shop in Clackamas, a suburb of Portland, called Inner Sound, appears to be up for this sort of work. The shop is maybe 120 miles/two hours away, over the Cascade Mountains. I live in Central Oregon - a fabulous place to live in spite of the fact that it's fairly provincial, without specialist services. Inner Sound is backed up to the tune of 90 days - my plan is to swap in a cheapie Yamaha that powers my garage/workbench in the interim. We will see how that goes Again, thanks. I really appreciate your input.

 

[TLS Guy]

Thanks very much for your replies, everyone. I think that I will have it repaired. A specialist shop in Clackamas, a suburb of Portland, called Inner Sound, appears to be up for this sort of work. The shop is maybe 120 miles/two hours away, over the Cascade Mountains. I live in Central Oregon - a fabulous place to live in spite of the fact that it's fairly provincial, without specialist services. Inner Sound is backed up to the tune of 90 days - my plan is to swap in a cheapie Yamaha that powers my garage/workbench in the interim. We will see how that goes Again, thanks. I really appreciate your input.

That may not be a wise course. It seems you have had better luck than most. These units seem quite problem prone. They are not easy to service. There are a lot of ICs in the unit. A common problem is in the power amps output stage. The power transistors are NLA, but there are used ones on eBay, and so called new old stock in China. The output devices are A1516.

What is this unit doing? Is it just dead? If so, a problem has probably caused the main fuse to blow. Or is the unit going into protection?

I would phone that technician in Clackamas and ask him if he has dealt with this receiver before and what success he has had.

In all honesty, I don't think this unit is worth a lot of expense. I think you have had more luck than most. We always used to say, NAD stands to Not Always Dependable.

 

[Inkstained]

Oh, OK, this is a valuable response. I'm getting distortion on both sides from all sources. The longer I listen to it, the worse it gets, finally trying to drop out the way a weak FM station will fade in and out. To your comment, I bought this thing new about 35 years ago. It has been dead reliable, so I guess I've been lucky. For what it's worth, I don't know what an IC is - I have no background in electronics. I'd be grateful for any further input you would care to offer. Thanks.

 

[TLS Guy]

Oh, OK, this is a valuable response. I'm getting distortion on both sides from all sources. The longer I listen to it, the worse it gets, finally trying to drop out the way a weak FM station will fade in and out. To your comment, I bought this thing new about 35 years ago. It has been dead reliable, so I guess I've been lucky. For what it's worth, I don't know what an IC is - I have no background in electronics. I'd be grateful for any further input you would care to offer. Thanks.

An integrated circuit, often called a 'chip' is a single micro component that contains complete circuits like operational amplifiers for instance, and many other diverse circuits. The problem is they are hard to manufacture and you have a major set up for each device. Set up costs just to manufacture one device runs into the millions of dollars. Because of this only one run is generally done, and only occasionally more. So when the supply is gone it is usually gone for good. So if an older unit has a failure of a chip no longer available it is done.

From the description of your fault my best guess is that the problem is likely in the power supply. So I suspect a reduced voltage, and decreasing voltage as heating occurs. So whether your unit is fixable is going to depend on whether the failed component is available. I have looked at the circuit and there are lots of ICs including in the power supply. My best guess is that a voltage regulator IC has failed, or may be a rectifier diode.
If an IC has failed then that is probably the end of the road. If it is a diode there is probably hope.

So, I guess if this guy is prepared to look at the unit for reasonable cost, the it should not take long to check voltages. If the cause is remedial, then you will luck out. If not the you have lost ground financially.

This really is an older design, and after looking at the circuits, I have to say it is packed with gratuitous complexity, which was a hallmark of that stable from my experience.

That is why I like Quad for older gear, and have lots of it. The circuits are so economical and elegant, as well as being well laid out, neat tidy. That was Peter Walker's hallmark.

 

[Eppie]

I think the amplifier stage could also be the culprit. IC003 looks like a monitoring circuit but the op has not mentioned any protect lights or the speaker relay not coming on. The 2SA1516 transistor is paired with the 2SC3907 and I can get 5 pairs for $26 Cdn, so if the output transistors are shot, it's not a big expense. Fortunately they are PNP / NPN power transistors, so odds of getting decent parts is good. (You have to be wary of fake parts with MOSFETs.) If it's further up the chain like IC601 and IC602 then the unit is likely scrap. It's a matter of whether it's worth the $50 to find out.

 

[TLS Guy]

I think the amplifier stage could also be the culprit. IC003 looks like a monitoring circuit but the op has not mentioned any protect lights or the speaker relay not coming on. The 2SA1516 transistor is paired with the 2SC3907 and I can get 5 pairs for $26 Cdn, so if the output transistors are shot, it's not a big expense. Fortunately they are PNP / NPN power transistors, so odds of getting decent parts is good. (You have to be wary of fake parts with MOSFETs.) If it's further up the chain like IC601 and IC602 then the unit is likely scrap. It's a matter of whether it's worth the $50 to find out.

According to others who have worked on these units, power transistor failure puts them into protection and the red light comes on. The fact that this involves both channels leads me to suspect the power supply as first suspect, but that is just a guess.

 

[Inkstained]

Again, thanks. This is great information. I just talked to the technician in Clackamas, where this shop, Inner Sound, is located. The service/diagnostic fee is $135. The tech offers no suggestions about what might be wrong with it but says it's probably fixable. The shop website lists NAD as one of the brands its services. I should note that this shop is the recommendation of the one audiophile shop here in Central Oregon. I guess we'll see.

 

[Inkstained]

I think the amplifier stage could also be the culprit. IC003 looks like a monitoring circuit but the op has not mentioned any protect lights or the speaker relay not coming on. The 2SA1516 transistor is paired with the 2SC3907 and I can get 5 pairs for $26 Cdn, so if the output transistors are shot, it's not a big expense. Fortunately they are PNP / NPN power transistors, so odds of getting decent parts is good. (You have to be wary of fake parts with MOSFETs.) If it's further up the chain like IC601 and IC602 then the unit is likely scrap. It's a matter of whether it's worth the $50 to find out.

According to others who have worked on these units, power transistor failure puts them into protection and the red light comes on. The fact that this involves both channels leads me to suspect the power supply as first suspect, but that is just a guess.

I have not seen any red light(s) come on. Everything on the fascia appears as normal.