I need to replace my Nad M25 Power amplifier.

[PENG]

Thanks again, I ordered all those parts.
Fuses did blow, I wonder why.
The capacitor burn through the board, I had to jump wire it, I hope it works.
Here are some photos:

http://imgur.com/a/E8paHFJ

If you can see clearly the damaged trace(s) only affect the capacitor's connections then the jumper method should be quick easy, but be very carefully to ensure you have the correct polarity as those are electrolytic caps. Also, as I mentioned before, test the unit before you put all the screws back on. If I were to do it myself, I wouldn't even put the covers on until it know it is working, like what they most likely would do in the repair shops. The safe way to do it is to put the covers back on so yo won't be exposed to any energized parts.

 

[Winkleswizard]

Since you seem to be willing to try the DIY approach, here are a few tips:

1. Be very careful to avoid shocking yourself. Wear a snug fitting glove/gloves to insulate your body from the circuit. Since you are working with high value caps, remember they keep can keep a charge even after power has been removed. Eye protection is also a good idea. If you manage to accidentally short something at high voltage, the arc can send hot metal fragments flying.

2. Do your best to isolate the circuit under repair/test. If you can readily disconnect the amp modules from the supply, should be one of the first things you do. Once repairs have been made, power up and measure the output voltage of the power supply to ensure your repairs have been successful. Next step would be to check your work under load. If you can, add one or 2 amp modules at a time. Also would suggest using some high wattage resistor and/or a cheap speaker as an initial load for the amp.

3. Your burnt circuit board area appears to have potentially bridged the adjacent circuit traces. Along with jumpering the open traces, you should ensure no new electrical path has been created. Depending on how hard the crud is, you may need to heat the area, but if just crusty, can use a small razor knife to carefully cut along thea area between the traces until you can be confident any potential circuit bridge has been eliminated.

If you do not have a variac or an isolation transformer, would do this work with as much circuit protection as you have available. At a minimum, use a surge protector. If you have ground fault protection outlet or can add one, would be a good idea too. Having fire extinguisher nearby is also a good precaution, but be sure it is rated for electrical fires.

Ww

 

[Pablo2k]

[QUOTE="TLS Guy, post: 1254004.[/QUOTE]

Good morning TLS Guy! I have two more question.
You told me I should be replacing:
C204 and 206 both Polyester caps 10nF, 10%, 100V
These have a number on them of 103J100 and when I ordered on Mouser I did not realized they had two different ones.
I ordered
Mfr. #: MMK5103J100J01L4BULK
Which are 0.01uF (10nF) 100V BUT 5% instead of 10% Tolerance.
I see that the do not have 10% in stock, only the 5%s

My question are:
Can I get away without changing them and see if it work without braking anything again?
Or
Can I get away with using these 5%?

Ps.
Also, does the size of a cap matter? one of them (C255 which is not on the your list, but I was thinking about replacing all of them) is exactly the same value, but about 2mm less in diameter.


Thank you again!

Pablo.

 

[TLS Guy]

[QUOTE="TLS Guy, post: 1254004.

Good morning TLS Guy! I have two more question.
You told me I should be replacing:
C204 and 206 both Polyester caps 10nF, 10%, 100V
These have a number on them of 103J100 and when I ordered on Mouser I did not realized they had two different ones.
I ordered
Mfr. #: MMK5103J100J01L4BULK
Which are 0.01uF (10nF) 100V BUT 5% instead of 10% Tolerance.
I see that the do not have 10% in stock, only the 5%s

My question are:
Can I get away without changing them and see if it work without braking anything again?
Or
Can I get away with using these 5%?

Ps.
Also, does the size of a cap matter? one of them (C255 which is not on the your list, but I was thinking about replacing all of them) is exactly the same value, but about 2mm less in diameter.


Thank you again!

Pablo.[/QUOTE]

5% is twice as good as 10% so yes you can use them. That is called an upgrade! Don't worry about the size, irrelevant.

 

[Pablo2k]

Good morning TLS Guy! I have two more question.
You told me I should be replacing:
C204 and 206 both Polyester caps 10nF, 10%, 100V
These have a number on them of 103J100 and when I ordered on Mouser I did not realized they had two different ones.
I ordered
Mfr. #: MMK5103J100J01L4BULK
Which are 0.01uF (10nF) 100V BUT 5% instead of 10% Tolerance.
I see that the do not have 10% in stock, only the 5%s

My question are:
Can I get away without changing them and see if it work without braking anything again?
Or
Can I get away with using these 5%?

Ps.
Also, does the size of a cap matter? one of them (C255 which is not on the your list, but I was thinking about replacing all of them) is exactly the same value, but about 2mm less in diameter.


Thank you again!

Pablo.

5% is twice as good as 10% so yes you can use them. That is called an upgrade! Don't worry about the size, irrelevant.[/QUOTE]

So I plugged it in, turn it on, relay clicked in, then all 7 led lights turned blue.
It looked good.
After about 18 seconds I hear a weird noise coming from the amp section, not the power supply.
It almost sounded like boiling water in a tea kettle but very faint. Like an old black and white TV turning on I guess, like something that was charging or building pressure.
I turn if off and that weird sound slowly went away, like something was being discharged or a pressure relieve valve slowly letting steam out, I really can’t discribe it.
Every time I turn it on it does that.
So I decided to give it a try anyway.
I’m getting no sound from any of the 7 amps.
The LEDs in front are blue and not RED which would mean a problems.
I wonder what it’s going on now.

 

[TLS Guy]

5% is twice as good as 10% so yes you can use them. That is called an upgrade! Don't worry about the size, irrelevant.

So I plugged it in, turn it on, relay clicked in, then all 7 led lights turned blue.
It looked good.
After about 18 seconds I hear a weird noise coming from the amp section, not the power supply.
It almost sounded like boiling water in a tea kettle but very faint. Like an old black and white TV turning on I guess, like something that was charging or building pressure.
I turn if off and that weird sound slowly went away, like something was being discharged or a pressure relieve valve slowly letting steam out, I really can’t discribe it.
Every time I turn it on it does that.
So I decided to give it a try anyway.
I’m getting no sound from any of the 7 amps.
The LEDs in front are blue and not RED which would mean a problems.
I wonder what it’s going on now.[/QUOTE]

Well that is what so often happens when you do a repair like this. That unit obviously has a very serious major problem. You gave it a good try, but obviously what you have repaired was the effect of a much more serious fault and not the cause of the failure.

I would expect repairs to be a major expense.

Since it is a NAD unit which honestly is pretty awful stuff, I would take it to the recycling center and get something better.

 

[Pablo2k]

Thank you for the honest and direct to the point answer!
What a shame... I did hear complains about Nad’s reliability in the past.
Someone gave me a Crown xti 4002 for $200 and I’m thinking about using it for the rear.
A coworker might sell me a Mcintosh MC126 which is only 80x6 but I can bridge it and get 275x3 and that would take care of the fronts...
He wants 800 I don’t know if is worth it.
We trying to work some things out.
We got to the point where I would give him $500 cash and a dslr which goes used for $1100 for:
McIntosh MX132 which I don’t need and has cracked glass.
Mcintosh MVP841 DVD cracked glass too.
Mcintosh CR16 not cracked but I also don’t need it.
Mcintosh MC126 not cracked and the one I want.
I can’t find those glasses anywhere and I hear they are expensive.
This stuff it’s all old and I might be in the same boat I am now in a year from now.
Another option it’s just two more Crown amps but XLS for 350 each.
Or spend more than double and get a Monoprice 200x5 but that’s my limit, it’s a little under $1500 shipped but 5 year warranty and made by ATI.

 

[KenM10759]

I respectfully disagree that NAD "is awful stuff". I've not have not had any issues which NAD tech support didn't solve immediately, and it was just one minor thing caused chiefly by me.

I'm still willing to take it and see if my friend who is a factory authorized service technician for Mesa, Boogie, Marshall and others might be able to revive it for me.

 

[Verdinut]

Thank you for the honest and direct to the point answer!
What a shame... I did hear complains about Nad’s reliability in the past.
Someone gave me a Crown xti 4002 for $200 and I’m thinking about using it for the rear.
A coworker might sell me a Mcintosh MC126 which is only 80x6 but I can bridge it and get 275x3 and that would take care of the fronts...
He wants 800 I don’t know if is worth it.
We trying to work some things out.
We got to the point where I would give him $500 cash and a dslr which goes used for $1100 for:
McIntosh MX132 which I don’t need and has cracked glass.
Mcintosh MVP841 DVD cracked glass too.
Mcintosh CR16 not cracked but I also don’t need it.
Mcintosh MC126 not cracked and the one I want.
I can’t find those glasses anywhere and I hear they are expensive.
This stuff it’s all old and I might be in the same boat I am now in a year from now.
Another option it’s just two more Crown amps but XLS for 350 each.
Or spend more than double and get a Monoprice 200x5 but that’s my limit, it’s a little under $1500 shipped but 5 year warranty and made by ATI.

Another option would be to get a QSC DCA 1824 which is a 4 channel cinema amplifier that is used in Cineplex theaters all across North America and worldwide.
I have one in my HT system to drive my surround speakers. This amplifier is solid like rock and weighs only 21 lbs. It has a power rating of 170 watts/ch at 8 ohms with all channels operating sumultaneously, excellent specs and you can't kill it!
It's not cheap. It sells for around US $1100 and has a 3 year warranty. It is made in the USA. A few online stores in California specializing in theater equipment sell it or you can get the info on a local dealer directly from QSC's website. Those DCA Series amps are not sold in pro audio shops.

https://www.qsc.com/cinema/products/power-amplifiers/dca-series/dca-1824/

My HT System: https://forums.audioholics.com/forums/threads/my-7-channel-system.111234/

Cheers,

 

[TLS Guy]

I respectfully disagree that NAD "is awful stuff". I've not have not had any issues which NAD tech support didn't solve immediately, and it was just one minor thing caused chiefly by me.

I'm still willing to take it and see if my friend who is a factory authorized service technician for Mesa, Boogie, Marshall and others might be able to revive it for me.

Each his own, but I can tell you I would not want to own anything from NAD, ever.

The C 370 goes into protection from a design error that there is a DIY fix for, as the circuit is available. Then they introduce the C 375BEE which does the same thing! Just look around the NET.

My father had NAD integrated that blew up. I spent the major junk of a vacation over there sorting it. It such an awful piece of you not what, I had to do extensive redesign, not just fix it. I was in so deep I added bass management along the way. That was at a time when bass management was not common.

You may have been lucky. As for me their gear is high up my not to be recommended list.

 

[TLS Guy]

Thank you for the honest and direct to the point answer!
What a shame... I did hear complains about Nad’s reliability in the past.
Someone gave me a Crown xti 4002 for $200 and I’m thinking about using it for the rear.
A coworker might sell me a Mcintosh MC126 which is only 80x6 but I can bridge it and get 275x3 and that would take care of the fronts...
He wants 800 I don’t know if is worth it.
We trying to work some things out.
We got to the point where I would give him $500 cash and a dslr which goes used for $1100 for:
McIntosh MX132 which I don’t need and has cracked glass.
Mcintosh MVP841 DVD cracked glass too.
Mcintosh CR16 not cracked but I also don’t need it.
Mcintosh MC126 not cracked and the one I want.
I can’t find those glasses anywhere and I hear they are expensive.
This stuff it’s all old and I might be in the same boat I am now in a year from now.
Another option it’s just two more Crown amps but XLS for 350 each.
Or spend more than double and get a Monoprice 200x5 but that’s my limit, it’s a little under $1500 shipped but 5 year warranty and made by ATI.

If you want the MC 126 go for it. Mac is reliable gear. Do not bridge it. Your speakers although specked 8 ohm nominal are not 8 ohm speakers, Nominal means "Sweet Fanny Adams." B & W do spec the minimum impedance as 3 ohm. So absent an impedance curve, the best guide to true impedance, is minimal impedance plus 10%. That makes your speaker 3.3 ohm and not 8. Any time you see two woofers you pretty much know the impedance will be 4 ohm or less. B & W are renowned for low impedance hard to drive loads. This does not imply they are bad speakers, but they do tend to stress amps. So a Mac may be a good choice. If you bridge an amp then the minimum impedance that it will handle is doubled. So the amp would require an 8 ohm load bridged.

In any event the Mac will deliver 120 watts into your speakers, which is plenty.

The B & W speakers very likely contributed to the demise of you NAD unit. I always advise robust amplification for B & W speakers. Although I have measured my friends B & W 800 D3s and they are a much easier drive than previous iterations of the B & W 800 speakers.

 

[Pablo2k]

I respectfully disagree that NAD "is awful stuff". I've not have not had any issues which NAD tech support didn't solve immediately, and it was just one minor thing caused chiefly by me.

I'm still willing to take it and see if my friend who is a factory authorized service technician for Mesa, Boogie, Marshall and others might be able to revive it for me.

It would cost more to ship lol
I still have all original double boxes, manuals etc for the M25 and M15HD2...
I might sell them both for $2k... I see the M15 on ebay for $1600 which is way overprice for non hd model.
Mine the M15HD upgraded to M15HD2; the module it self cost me $700 and then it had to be installed and firmware upgraded.
The problem with this stuff is that is big and heavy; the box and the M25 weights about 105lbs. and the size of the box is way oversize.

 

[Pablo2k]

If you want the MC 126 go for it. Mac is reliable gear. Do not bridge it. Your speakers although specked 8 ohm nominal are not 8 ohm speakers, Nominal means "Sweet Fanny Adams." B & W do spec the minimum impedance as 3 ohm. So absent an impedance curve, the best guide to true impedance, is minimal impedance plus 10%. That makes your speaker 3.3 ohm and not 8. Any time you see two woofers you pretty much know the impedance will be 4 ohm or less. B & W are renowned for low impedance hard to drive loads. This does not imply they are bad speakers, but they do tend to stress amps. So a Mac may be a good choice. If you bridge an amp then the minimum impedance that it will handle is doubled. So the amp would require an 8 ohm load bridged.

In any event the Mac will deliver 120 watts into your speakers, which is plenty.

The B & W speakers very likely contributed to the demise of you NAD unit. I always advise robust amplification for B & W speakers. Although I have measured my friends B & W 800 D3s and they are a much easier drive than previous iterations of the B & W 800 speakers.

My little speakers are 3.3ohms? I have the 600 series, not the 800 series.
683s, 684, htm61
I was hoping to bridge the MC126 because it says its only 80w at 8ohms.
Bridge, three channels is 275w at 8ohms.

 

[PENG]

So I plugged it in, turn it on, relay clicked in, then all 7 led lights turned blue.
It looked good.
After about 18 seconds I hear a weird noise coming from the amp section, not the power supply.
It almost sounded like boiling water in a tea kettle but very faint. Like an old black and white TV turning on I guess, like something that was charging or building pressure.
I turn if off and that weird sound slowly went away, like something was being discharged or a pressure relieve valve slowly letting steam out, I really can’t discribe it.
Every time I turn it on it does that.
So I decided to give it a try anyway.
I’m getting no sound from any of the 7 amps.
The LEDs in front are blue and not RED which would mean a problems.
I wonder what it’s going on now.

If there is a nearby reputable repair shop that may not be NAD authorized but authorized for other brands' mid to high end amplifiers, then it is worth getting an estimate from them. They may charge $75 to $125 for the diagnostics.

I think it is worth the risk because:
1. The original damage happened when the unit was off, but plugged in, right?
2. The sign of damage (that one cap with visible sign) supports 1) above, because the only visible damage appears to be on the standby power circuit. If I remember wrong about 1),then ignore my suggestion for sure.

If the voltage/current spike had fried something else, there would likely be other visible signs, or even some residual smell. The thing is, you have only replaced a few caps but not all the components on that circuit, and the damaged PCB copper trace may have affected other areas.

The diagnostic cost will likely be less than the shipping cost to KenM10759, or me.

 

[PENG]

My little speakers are 3.3ohms? I have the 600 series, not the 800 series.
683s, 684, htm61
I was hoping to bridge the MC126 because it says its only 80w at 8ohms.
Bridge, three channels is 275w at 8ohms.

No the S2 version would dip to 3 ohm, but overall I would rate them 4 ohms and your NAD amp should have been able to drive any B&W 683 speakers easily. B&W recommended 20-200 W for the S2 version, the original version appeared to have similar impedance ( and phase characteristics.

From B&W website:
Recommended amplifier power25W - 200W into 8Ω on unclipped programme

The M25, though ridiculously week for it's 115 lbs weight, is capable of 160 W continuous (ACD) into 4 ohms and 485 W into 2 ohms for a split second.

The power you need is determined by the application so I highly recommend you use an online calculator such as the one linked below to figure things out before your next amp purchase.

http://myhometheater.homestead.com/splcalculator.html

After that, we can all agree on at least one thing, how much power you really need for your speakers in you room and for you only.

To put things in perspective, there are no shortage of people on various forums who claimed my little LS50 speakers need a lot of power to sound good, yet I am now using a cheap and light weight AVR-X3400H, and they sound just as good as my Halo A21 2 X 250 W amp that weighs 62 lbs. If anyone can score better than say 15 out of 20 in a SBT in my place, he/she can take it for free. I also did drive them with my 5 W X 2 amp and they sounded just as good too, but obviously couldn't play as loud. To say all amps would sound the same, without qualifications/caveats is ridiculous, but the same could be said about needing certain amps for certain speakers for them to sound their best. For examples, all those brands suggested to you so far, Crown audio, QSC, Monolith etc., could all do the job, and you just have to figure out how much power you really need, before finalizing on the specific models.

 

[Pablo2k]

If there is a nearby reputable repair shop that may not be NAD authorized but authorized for other brands' mid to high end amplifiers, then it is worth getting an estimate from them. They may charge $75 to $125 for the diagnostics.

I think it is worth the risk because:
1. The original damage happened when the unit was off, but plugged in, right?
2. The sign of damage (that one cap with visible sign) supports 1) above, because the only visible damage appears to be on the standby power circuit. If I remember wrong about 1),then ignore my suggestion for sure.

If the voltage/current spike had fried something else, there would likely be other visible signs, or even some residual smell. The thing is, you have only replaced a few caps but not all the components on that circuit, and the damaged PCB copper trace may have affected other areas.

The diagnostic cost will likely be less than the shipping cost to KenM10759, or me.

Yes, it might not be now, but I will bring it because you never know.
It happened while it was on, I was getting ready to watch a movie, so it probably happened after the relays clicked on.

PENG,
What do you think about the McIntosh stuff I listed?
He says he will give me:
McIntosh
MX132 broken glass but working.
MVP841 DVD broken glass also.
CR16 good
MC126 good
Kef center channel, forgot which one but big.
Rel subwoofer q400e
JVC DLA needs bulb he says.

And I would give him:
$500 cash
Nikon D800 (goes for 900-1000 on eBay)
Nikon 85 1.8 afs (goes for 300-350 on eBay)
Nikon TC17ii (goes for 200-240 on eBay)
I hear McIntosh glass is very expensive and anyways I can’t find it on line and it’s old stuff.
There is a MC126 on eBay right now asking 1599 but it’s not selling.
I really only need his MC126 but by it self he wants too much and as a package like I listed I would get other things I might be able to trade in the future.
Thank you and sorry all the questions!
Pablo.

 

[PENG]

Yes, it might not be now, but I will bring it because you never know.
It happened while it was on, I was getting ready to watch a movie, so it probably happened after the relays clicked on.

PENG,
What do you think about the McIntosh stuff I listed?
He says he will give me:
McIntosh
MX132 broken glass but working.
MVP841 DVD broken glass also.
CR16 good
MC126 good
Kef center channel, forgot which one but big.
Rel subwoofer q400e
JVC DLA needs bulb he says.

And I would give him:
$500 cash
Nikon D800 (goes for 900-1000 on eBay)
Nikon 85 1.8 afs (goes for 300-350 on eBay)
Nikon TC17ii (goes for 200-240 on eBay)
I hear McIntosh glass is very expensive and anyways I can’t find it on line and it’s old stuff.
There is a MC126 on eBay right now asking 1599 but it’s not selling.
I really only need his MC126 but by it self he wants too much and as a package like I listed I would get other things I might be able to trade in the future.
Thank you and sorry all the questions!
Pablo.

The only good one I see is the MC126 but it is not very powerful unless you bridge it. You really shouldn't bridge it due to the B&W683's low impedance.

Seems to me getting a new AVR or a prepro if you must, plus the Monolith 5X200 (or equivalent number of pro amps) really the way to go. In general, on the electronic side of things, keep it simple and stupid, and go with the latest technology, is better than living in the past..

By the way, I have spent enough hours on comparing things, to know that you can't beat the benefits of REQ, in terms of more bang for the buck than spending much more on amps and preamps. I know people like TLSGuy will probably never agree, but you owe it to yourself to be open minded and give it a try.

 

[PENG]

Yes, it might not be now, but I will bring it because you never know.
It happened while it was on, I was getting ready to watch a movie, so it probably happened after the relays clicked on.

I don't know how I got the wrong impression that it was off. So my 2 cents were irrelevant. Sorry!

 

[Verdinut]

Thank you for the honest and direct to the point answer!
What a shame... I did hear complains about Nad’s reliability in the past.
Someone gave me a Crown xti 4002 for $200 and I’m thinking about using it for the rear.
A coworker might sell me a Mcintosh MC126 which is only 80x6 but I can bridge it and get 275x3 and that would take care of the fronts...
He wants 800 I don’t know if is worth it.
We trying to work some things out.
We got to the point where I would give him $500 cash and a dslr which goes used for $1100 for:
McIntosh MX132 which I don’t need and has cracked glass.
Mcintosh MVP841 DVD cracked glass too.
Mcintosh CR16 not cracked but I also don’t need it.
Mcintosh MC126 not cracked and the one I want.
I can’t find those glasses anywhere and I hear they are expensive.
This stuff it’s all old and I might be in the same boat I am now in a year from now.
Another option it’s just two more Crown amps but XLS for 350 each.
Or spend more than double and get a Monoprice 200x5 but that’s my limit, it’s a little under $1500 shipped but 5 year warranty and made by ATI.

By the way, I had forgotten to mention that the QSC DCA 1824 will output 250 watts/ch at 4 ohms and is able to handle impedance curves going down to 2 ohms without a hitch.
That would take care of the surround and rear surround speakers if you want to go for a 7 channel system. For the front channels, I would suggest the Monolith 3 X 200w.
Another option fot the front channels would be to get two DCA 1222s, but you would have an extra amp with no use for it.
My 2 cents.

 

[M Code]

My little speakers are 3.3ohms? I have the 600 series, not the 800 series.
683s, 684, htm61
I was hoping to bridge the MC126 because it says its only 80w at 8ohms.
Bridge, three channels is 275w at 8ohms.

Pablo..
Do not use a bridged amplifier with those loudspeakers..
Typically, a bridged amplifier for home applications do not like low impedance loads..
If U want or need the high power, procure an amplifier that is capable of putting out the target spec without bridging..

Just my $0.02...