Advice on electronics repair - how badly have I bricked my DAC?

[nerrrd]

So I have a nice NAD combination DAC and headphone amplifier which I've enjoyed listening to for some years now, that was until I was reorganising things in my flat during the last lockdown in Auckland and accidentally plugged the wrong AC adapter into it.

So instead of getting the required 5V DC input, it ended up getting (I think) 22V for a couple of seconds before I saw the wisps of smoke coming out of it and unplugged it as quickly as I could. Suffice to say the burnt electronics smell lasted for a few days.

Now with the correct adapter plugged in the standby power light comes on but not surprisingly it won't switch on.

I got in touch with the place I bought it at the time and they quoted $90 just for a diagnosis with any repair costs on top of that. It is admittedly now a bit out of date but I like it and if I could get it working again I would feel a whole lot less stupid.

Unfortunately I have no income at the moment so $90 is a sizeable amount to write off if a repair isn't feasible, so just wondering if anyone out there could advise me how badly pouring 22V into a 5V power supply even for a few seconds is likely to damage what I guess are some fairly delicate circuits inside.

My expectation is that the smoke and the burning smell probably indicates a fatal blow, just looking for an unbiased confirmation of that really. Thanks in advance.

[FJRider]

so just wondering if anyone out there could advise me how badly pouring 22V into a 5V power supply even for a few seconds is likely to damage what I guess are some fairly delicate circuits inside.

Connect your flat to a 1000 volt system and compare the result. Four times the voltage it was designed for.

My expectation is that the smoke and the burning smell probably indicates a fatal blow, just looking for an unbiased confirmation of that really. Thanks in advance.

Although I'm no electrician ... I would surmise your expectation is correct.

My recommendation is not waste money getting that confirmed. Spend that money on a new one.

[slofox]

I'd say it was fucked, wouldn' you?

I think I'd skip the $90 bit too. Last time I had that thrown at me (a different product), I compared the price of a new one and it was only $29 more than "examination" of the old one.

[eldog]

Its the smoke thats the dead give away with electrical goods.

I worked with 2 electricians recently, they both said the smoke injection machine was the most underrated piece of equipment they owned

[nerrrd]

Failing one of those smoke injecting machines, a delay like they have on the radio would be very useful in real life, just a few extra seconds to catch the stupid before it’s too late.

Thanks I’ll save myself the $90 then and turn it into an ashtray or something equally useful these days.

[pete376403]

Can you get the cover off and the circuit board out? You may have fried everything or it may be a single component that can be replaced.
Put up a photo of the damage

[SaferRides]

Definitely worth a look inside. You may have just taken out a voltage regulator for example.

What is it worth?



Sent from my SM-G980F using Tapatalk

[nerrrd]

I’ll definitely give opening it up a go as soon as I get back to it.

Was a bit of an extravagance for me at the time but at the low end of the audio price spectrum, I think i got it on special for $599.

[SaferRides]

I’ll definitely give opening it up a go as soon as I get back to it.

Was a bit of an extravagance for me at the time but at the low end of the audio price spectrum, I think i got it on special for $599.

Definitely worth making an effort then. I rescued a phono preamp about 10 years ago by replacing the power supply caps. It's still going strong.

Sent from my SM-G980F using Tapatalk

[TheDemonLord]

You just need to gather up all the Magic Smoke, and carefully put it back into the relevant components.

[FJRider]

You just need to gather up all the Magic Smoke, and carefully put it back into the relevant components.

I think the Genie has left the building ...

[nerrrd]

So, who knew electronics could be so complicated...I'm starting to appreciate why they charge $90 just to look at this kind of thing.

So I have no idea what I'm looking at, but I can't see any obvious evidence of damage, or where the magic smoke goes. Here are some images from around the power connector anyways for your amusement.



At this point I'm thinking of making it into some kind of collage.

[Berries]

What happens if you pull that bit of chewing gum off it?

[nerrrd]

Don't think it'll show much? The circular wrapped wire thingy under it looks unscathed.

[neels]

The block diagram shows a protect cct on the 5V front end, if you're lucky it's designed to guard against what you did....



Circuit diagram looks like a reverse polarity protection diode, then some filtering and a couple of series pass transistors, if you don't have 5V I or 5V D where it's shown, it's on the input side.



If 5V D is present across C734 then it's further downstream and a bit uglier, as there are a bunch of psu circuits that need to be checked, if one of them is missing it won't go...



That's about all I can do from where I'm sitting, other than point you at the Service Manual that google found for me...