Audio-gd nfb11.28 amp power issues

[terrorc0n]

Hey guys

I recently picked one these amps up cheaply locally and have been using and enjoying the upgrade from what I was using previously.

Though in the last week I was using the amp and noticed a bit of a smell but the amp was still working. Now whenever I power the amp on, it’ll work for between 5 minutes to an hour maximum and then power off.
Power cycling does nothing to remedy the issue.
I’ve found leaving it for even up to 30 minutes it will work again but for the same time window as previously stated.

Any help with repairing this would be greatly appreciated if at all possible.

Thanks!

 

[Sokel]

Is that the back side of the IEC in the second pic?
WTF???

I would stay far and away from this thing.

 

[terrorc0n]

Is that the back side of the IEC in the second pic?
WTF???

I would stay far and away from this thing.

It’s covered in a lot of hot glue, I guess to hold everything in place, not ideal of course.
This is how they come when they’re manufactured as far as I believe.

 

[Sokel]

It’s covered in a lot of hot glue, I guess to hold everything in place, not ideal of course.
This is how they come when they’re manufactured as far as I believe.

The burning all around it along with solder remains can only tell me that it was repaired as is,assembled.
Even an amateur would not create such havoc soldering.

All these solder remains can very well short things.

 

[terrorc0n]

The burning all around it along with solder remains can only tell me that it was repaired as is,assembled.
Even an amateur would not create such havoc soldering.

All these solder remains can very well short things.

There’s nothing burnt on the back of the IEC input, I think it’s just how the hot glue looks in the photo. The phase a neutral have been soldered in the back correctly, they’ve just covered it in hot glue to keep it all in place for whatever reason.
On the manufacturer website this is what they look like.

 

[Sokel]

There’s nothing burnt on the back of the IEC input, I think it’s just how the hot glue looks in the photo. The phase a neutral have been soldered in the back correctly, they’ve just covered it in hot glue to keep it all in place for whatever reason.
On the manufacturer website this is what they look like.

I hope it's the pic then.
I does show deformed though and the marked one seem like solder to me.

Maybe a hires close pic can tell us more.

 

[JSmith]

Though in the last week I was using the amp and noticed a bit of a smell but the amp was still working.

Was it quite hot at the time? What you describe sounds like it may be related to overheating, which may be why it works again after cooling down.

If components were defective it would generally only stay on for a short moment.

Does your phone have thermal imaging? If so, maybe we can ascertain what is getting too hot.


JSmith

 

[Lupin]

Well my NFB-11.38 looks a lot cleaner than that... looks like someone used that unit for solder practise or something.

 

[terrorc0n]

Here are some more pictures, hopefully these are clearer.
I’d be happy if it were just swapping out the IEC input, would be a easy fix.

 

[Sokel]

Here are some more pictures, hopefully these are clearer.
I’d be happy if it were just swapping out the IEC input, would be a easy fix.

They are clearer and is just as bad as I thought.
I would replace that regardless the fault that it may be down the road.

You can actually scrap these solder remains with a little knife yourself to see them (make sure they don't fall into the amp,they will short things even more)
That's not a job of a pro.

 

[terrorc0n]

They are clearer and is just as bad as I thought.
I would replace that regardless the fault that it may be down the road.

You can actually scrap these solder remains with a little knife yourself to see them (make sure they don't fall into the amp,they will short things even more)
That's not a job of a pro.

That’s easy enough to do thankfully.
Is it likely that’s what could be causing the issue?
I’m hoping it’s not the power supply, doubtful I’d get a replacement.

 

[terrorc0n]

Was it quite hot at the time? What you describe sounds like it may be related to overheating, which may be why it works again after cooling down.

If components were defective it would generally only stay on for a short moment.

Does your phone have thermal imaging? If so, maybe we can ascertain what is getting too hot.


JSmith

I wouldn’t say quite hot, but warm to the touch, nothing out of the ordinary for other amps I’ve used over the years.

I did initially think overheating, but this evening when I have run it, I had it on for about 3 minutes before it shut off, which It definitely was not warm enough for me to think that.

 

[Sokel]

That’s easy enough to do thankfully.
Is it likely that’s what could be causing the issue?
I’m hoping it’s not the power supply, doubtful I’d get a replacement.

Probably it's not the issue but it indicates something fishy about the amp,certainly someone not qualified did something to it and tried to solder the IEC as it was without disassembling it.

Let's see what other members have to say ,@restorer-john is a master at it,@Doodski has also repaired lots of amps.

 

[Doodski]

The workmanship is horrible for sure. How did you come to own this unit @terrorc0n? How long have you had it? How long has the fault existed? Other than the rear panel connector replacement the unit for mortals is non-serviceable.

 

[terrorc0n]

The workmanship is horrible for sure. How did you come to own this unit @terrorc0n? How long have you had it? How long has the fault existed? Other than the rear panel connector replacement the unit for mortals is non-serviceable.

It was for sale on Facebook marketplace locally for $30, had some really good reviews online and ticked a lot of boxes for what I was wanting.

Equipment like this isn’t super common in my country and can be fairly expensive so doesn’t come up often.

I’ve had it for around a month or so and it has been working fine up until the last week.

 

[Doodski]

It was for sale on Facebook marketplace locally for $30, had some really good reviews online and ticked a lot of boxes for what I was wanting.

Equipment like this isn’t super common in my country and can be fairly expensive so doesn’t come up often.

For $30 it was a good gamble.

I’ve had it for around a month or so and it has been working fine up until the last week.

I see.

With blurry and black images it is a bit tricky seeing what is exactly there. I am suspect of that connector block. Yes, I have in rare circumstances seen connectors cause the fault you describe where it turns off after a few minutes or 30 minutes. If me (A techy) I would get to the connector block terminations and see what is there inside the messy glue stuff. Is that like JB Weld or hot glue? What would you describe it as?

The other option is to bypass the connector entirely by using wires (Like small alligator clips or better.) and jumper around the connector and see how it works then. That way you can avoid making a mess by picking apart the glue stuff. This unit requires a qualified techy or engineer.

 

[Doodski]

I am searching out images of the unit to see how others look at the connector... brb.

 

[Doodski]

It appears the glue is here too but is neater looking.

 

[Doodski]

@terrorc0n I think your best choice is to send it to a tech or engineer for service.

 

[terrorc0n]

Thanks for the input I appreciate it, I have some spare IEC inputs at work, so as you say I might jumper them across and bypass that mess that’s there and see what happens.
To be fair there’s not really anywhere I can send it, places in my country tend to either only repair reputable vintage equipment or send anything else to the manufacturer.
Usually I’m a lot more game to give things a go, just not as versed with obscure Chinese amps