NAD 3060 no output

[Markoneswift]

Or make some yourself. A couple a short lengths of high quality cable and four quality RCA males. Bit of solder, done

 

[Markoneswift]

Or do a search for 'amp jumpers', there's a crap load of them

 

[Peter Newman]

Thanks and I am still working on your other suggestions

I still cannot see why the phono input isn't working with a known good TT but the IPod on AUX In is working. Wouldn't it be pretty well using the same circuit but just going via the input selector switch.

Some of the pots are hard to access with the contact spray and actually soldered into the PCB, and so are a major hassle to remove to gain access to clean. It was never going to be too easy

 

[Peter Newman]

Thanks Inductor so another potential area for that problem.

 

[Peter Newman]

Still not much luck here aside from trying to narrow down the problem area/s by using rudimentary methods with what I have available.

• Next - how do headphones sound ? One channel still weak ?

• there is no headphone jack fitted just a hole where it should be so this is not possible.

• The “try patching the preamp side of the NAD to this other unit and that would help to identify if the problem in the NAD is in the preamp or power amp section” is another good idea and I’ll have to see what I can come up with. Worth a try

• the only thing that I have is a small guitar amp so I plugged the pre-amp output into this, one channel at a time with the balance control centred and the volume level is consistent in both channels. To me this indicates that the problem is in the main amp? Well the volume differential between channels problem anyway.

So I can deduce? that the low volume problem is in the main amp in the right channel (if I swap the IPod output from one AUX input to the other the low volume is always on the right channel)

The other main problem is that neither phono input channel is working, either with known good TT input of IPod input. So this based on

the phono in goes thru an eq cct

would indicate that this EQ circuit on both channels is faulty discounting something like the channel input selector switch being faulty? I have used an aerosol contact cleaner on all pots, switches and input jacks etc to no avail. Lastly to non operational bulb in one VU meter, a minor problem but it still needs to be fixed. I am unsure of what technology these globes are but I have checked the voltage on both sides of both bulbs and it is a nominal 20.8v. This is perplexing, well to me as that indicates that there is continuity on the U/S bulb and a good power supply but it still does not illuminate.

I am unsure as to whether this 3080 schematic that I have is basically the same as my 3060. From the low res photos and schematic / PCB connection diagrams they appear very similar but not 100% the same but it's all I have.

Based of all my ravings and rudimentary "diagnosis " where should I be heading now do you think. Should I be getting a signal generator and attempting to try and isolate the low output channel and trace through it or would I be better off just attempting to replace all the caps in either the suspect channel (assuming I can ID them from the ones in the operational channel) or is there some other easier things that I could try first. Some other easier to replace components that could be the cause of the problem/s (low output and non functional phono in channels) Thanks for reading my convoluted story and hoping for any more clues, tips or advice.

 

[Markoneswift]

Well, there is a fairly 'rudimentary' device you can build which although very basic dies actually work wonders. Have a look for videos or instructions on how to build an audio probe - I made mine from basic materials and a set of old amplified computer speakers.

You can use a tone generator app on a phone to inject a steady tone into the amp, the trace it through the circuit using the audio probe. I did this technique and was able to pinpoint precisely where a signal became weak in one channel. Of course for this kind of work you really need a scope, but the probe works well enough.

What's the history of the amp ? Do you know why there is no headphone socket ? If someone has messed with it and removed the socket then that might be causing your problem.

 

[Peter Newman]

Thanks for that tip, I'll knock up an audio probe and seeing as I don't have a smart phone - yeah I know, it's sad I'll use something like TrueRTA for the tone generator and see what I can find.

As for the history of the amp, I wouldn't have a clue about it or why the headphone socket is missing. I'll have a good look around that area and make sure that it's removal hasn't done something to cause the low output on one channel.

This guy is diagnosing a valve based amp rather than a solid state like my amp but I assume the procedure is basically the same is it. Does this guy seem to know what he is talking about please

Also I just have to work out how and where they are getting the TrueRTA signal out of the PC from I suppose the sound card output?

 

[Markoneswift]

The video is exactly what I am talking about, I followed his instructions for making a probe and it works great. The process is basically the same - start from a point as close to the signal input as possible and then 'sniff' along the traces and components until you hear a drop or degradation of the signal.

If I get chance at work later, I will have a look at the 3080 schematic and see if there are any obvious points you should check. If the headphone jack has been removed, rather than never fitted in the first place, I would sniff around there for starters.

You can also use the probe to work through the phono preamp and equaliser circuit to find out where the signal cuts out. I would concentrate first on tracing a known good signal though, IE from your IPod or computer through the AUX input. Your computer will just use the soundcard line out, most likely a stereo 3.5 mil jack.

 

[Markoneswift]

The headphone jack issue may be a red herring but if it was removed then the connections should have been bridged to ensure continuity of the signal.

If you get down to testing individual components then you are going to need to remove them from the circuit to properly test them. Are you OK with soldering / desoldering ?

 

[Peter Newman]

I was thinking that the headphone jack removal would not cause the low output situation but I will ensure that has been bypassed correctly.

Most likely a waste of time but I have asked NAD about the proper schematic for my 3060 so I'll see how I go. Optimistic aren't I The 3080 one appears to be pretty similar but regardless that is all I have to work from. I was just trying to look at the boards and differentiate between channels in the power amp. I suppose that I can also compare voltages at different points between the functional and low output channels?

About to go the Jaycar and see if they have that cap for the audio probe and I'll then try and sort out the TrueRTA tone generator to save having to use a guitar signal to do that. I might also buy the Deoxit aerosol (30 bucks OUCH) as it might be handy to have a good heavy duty cleaner on hand as well as the normal spray cleaner I got there the other day.

I would concentrate first on tracing a known good signal though, IE from your IPod or computer through the AUX input.

So just use the IPod as an input into the working AUX channels and trace the signal to get a feel for how it's done you mean?

If you get down to testing individual components then you are going to need to remove them from the circuit to properly test them. Are you OK with soldering / desoldering ?

Yes so resistors can be tested in circuit but not caps as far as I am aware?
Yes I am comfortable with soldering / desoldering and luckily I have some good MG Chemicals flux and Goot wick from my quadcopter PCB work.

Thanks for all your help so far Makoneswift it's very generous of you and I appreciate it.

 

[Markoneswift]

I just use the Servisol contact cleaner / solvent that Jaycar sell - seems to do the trick.

Use IPod through Aux to trace where the signal drops / goes weak because all input sources go through the preamp and power amp so if you notice a distinct issue somewhere along the path, that is where the problem lies.

Resistors, diodes, transistors all need at least one leg lifting to test properly. Really transistors need to be removed fully to test. If you do any testing in circuit, you will likely get false reads from other components nearby such as resistors in series etc.

Happy to help, there are many guys and gals on here who know way more than I do but I will try to help you with basic stuff where I can.

 

[Markoneswift]

Can you try to measure the DC output of your speaker terminals ? Set all tone controls and balance to middle, volume low, no input source.

 

[Peter Newman]

I'll save my 30 bucks then because that Servisol is what I got the other day. Oh I see what you mean sorry. IPod input into AUX and trace the signal on the low output channel to where it goes weak.

Yes you mentioned that test at the speaker outputs right when you first started helping me but I have not done it yet. I'll do it now.
Both started at about 47 - 48mV but drop the longer I leave the DMM connected?

 

[Markoneswift]

I'll save my 30 bucks then because that Servisol is what I got the other day. Oh I see what you mean sorry. IPod input into AUX and trace the signal on the low output channel to where it goes weak.

Yes you mentioned that test at the speaker outputs right when you first started helping me but I have not done it yet. I'll do it now.
Both started at about 47 - 48mV but drop the longer I leave the DMM connected?

They sound a bit high, but not massive. There's likely a couple of pots on the amp that you can adjust to bring those down but you need to know what the stock figures should be first.

 

[Peter Newman]

What like trim pots on the PCB type thing? I am having trouble locating the cap locally for the audio probe but if worse comes to worst I can include some in a Digikey order I will be doing

 

[Markoneswift]

The schematic for the 3080 is not really helpful I'm afraid. It gives component values and wire colours but doesn't give any voltages for E,B,C of any transistors etc like most do. Without expected voltages listed, it's hard to tell whether the machine is running to its design parameters or not. It does mention about checking idle current, but only with the addition of parallel resistors etc which you probably don't want to get into.

I think that given the low quality of the manual, probing might give some success. I found the cap for the probe at Jaycar - I don't think it was an exact match but close. Its function is to prevent the DC current from going up the probe so value is not too critical.

 

[Peter Newman]

I have contacted NAD about a schematic as I think I mentioned but yes, I feel that was ******* in the wind I have ordered some of these caps from RS Components and they will be here in the morning.

I did ask in another thread about their suitability for the audio probe despite not being an ideal physical shape. What are your thoughts please?

I was thinking that it may be possibly to compare some voltages between components in the working channel against those on the low output channel? A big ask for a rank amateur but I have nothing to lose.

 

[Markoneswift]

Those caps look OK I think I might have used something similar in mine.

Comparing voltages between channels will give you some idea of where the problem might be. Combine that with some probing and hopefully you will get somewhere.

 

[Peter Newman]

Thanks I got the caps today so I'll have a poke around