Is my amp dead for good?

[Old Garage-Bander]

On some products there is a standby supply always connected across the line. If this is the case, the standby supply is almost surely damaged. The standby supply handles housekeeping tasks along with power-up and auto voltage configuration before the main supply stabilizes.

This is not user serviceable.

Ah yes! The standby supply. Of course.
The power that operates the power-on or boot-up circuits.

This is like with a TV set for instance.
You shut it off and on with a remote control.
But when it is "off," it is never fully off or you wouldn't be able to turn it on from your couch.

We need to treat our other consumer electronics, Like we treat our computers.
If they are plugged into the wall, they are at risk.

 

[beans-on-toast]

If the problem lies within the amp and the fuses are ok, it is possible that the part circled below has blown open. It is a type NTC 10D-11 thermistor.

 

[seamonkey]

What does TC say?
Maybe they are aware of this behavior, and know a user way to fix it, ...
Their support is pretty good in general

 

[subdude67]

If the problem lies within the amp and the fuses are ok, it is possible that the part circled below has blown open. It is a type NTC D10-11 thermistor

beans-on-toast, that was spot on! I bent it over and found this:

Is there anything else I should be looking for?

 

[beans-on-toast]

beans-on-toast, that was spot on! I bent it over and found this:

View attachment 2866333

Is there anything else I should be looking for?

It is designed to expire when stressed. Hopefully that is the only problem. It wouldn’t hurt to order spare fuses at the same time.

 

[dbsfgyd1]

Any idea what parts would be affected by this? The internals of the amp look perfect, there is nothing visibly melted, burned or otherwise suspicious?

Just asking, but did you check the electrical outlet that you use to plug the amp in?

 

[subdude67]

Just asking, but did you check the electrical outlet that you use to plug the amp in?

I tried the amp with 3 different cables on 7 different sockets in 3 locations with the same result, not working.

 

[Engle]

beans-on-toast, that was spot on! I bent it over and found this:

View attachment 2866333

Is there anything else I should be looking for?

Nice! Let us know what happens.

 

[DrummerwStrings]

Hopefully it's just that part that's blown.

Mods can weigh in if this is Off topic - does home/renter's insurance cover the fried lighting & appliances?

 

[agedhorse]

It is designed to blow. Hopefully that is the problem. It wouldn’t hurt to order spare fuses at the same time.

No, they are not designed to blow. They can fail due to improper design, or to excessive energy dissipation caused by current flowing through it plus a high impressed voltage (such as an overvoltage fault).

If you choose to replace the part, be aware that you really must use a current limited AC supply when powering up because additional damage may be present. If this is the case, the thermistor can explode under fault conditions resulting in injury. This is a very real hazard, plus it can scare the crap out of you when it happens.

This is where a little bit of knowledge can be dangerous, so use caution if you choose to "wing it".

 

[subdude67]

Hopefully it's just that part that's blown.

Mods can weigh in if this is Off topic - does home/renter's insurance cover the fried lighting & appliances?

I have asked a shop to find a replacement, I will report on the progress! And thanks again for all who chimed in, this is a truly amazing community!

Regarding the insurance, the owner of any property that has suffered damage due to technical faults from the grid can make a claim with the Kenya Power & Lighting company but we will sooner have an over the counter cure for cancer before there will ever be made a compensation to a private citizen.

The owner cannot be sued because it has nothing to do with the house or the wiring, wich in this case is done to german standards. Not one of the trip switches or breakers went off. But every appliance that was plugged in, operating or not was damaged as was every light that was turned on during the event.
But there are many up sides too to living here

 

[BadExample]

I had a ceramic mil-spec op amp blow up in my face. Minding my own biz, didn't touch it, just looking for a test point. That hurt.

 

[DrummerwStrings]

a little bit of knowledge can be dangerous

Found my epitaph.

 

[beans-on-toast]

To be clear, a thermistor is not a fuse.

When subjected to stress beyond the design limits, unable to dissipate the excessive energy as you said, they fail. In this case, blowing implies opening the circuit. Better that than a short. Being where they are in the primary transformer circuit, it isn’t unusual that they fail when hit hard with over voltage and current as is often seen with power line lightning strikes. Beyond their power up current limiting capacity, thermistors are used as added circuit protection devices.

No, they are not designed to blow. They can fail due to improper design, or to excessive energy dissipation caused by current flowing through it plus a high impressed voltage (such as an overvoltage fault).

 

[subdude67]

No, they are not designed to blow. They can fail due to improper design, or to excessive energy dissipation caused by current flowing through it plus a high impressed voltage (such as an overvoltage fault).

If you choose to replace the part, be aware that you really must use a current limited AC supply when powering up because additional damage may be present. If this is the case, the thermistor can explode under fault conditions resulting in injury. This is a very real hazard, plus it can scare the crap out of you when it happens.

This is where a little bit of knowledge can be dangerous, so use caution if you choose to "wing it".

Thanks a lot for your advice!

Let me ask, if I find an identical thermistor, is there more to it than to remove the original one and solder in the replacement?

The limited current power supply you mention, what exactly is it?

I apologise for asking but I cannot simply go to a store and ask for something that I don't know exactly what it is supposed to do.

 

[David A. Davis]

current limited AC supply

Do you mean a variac?

 

[byacey]

On some products there is a standby supply always connected across the line. If this is the case, the standby supply is almost surely damaged. The standby supply handles housekeeping tasks along with power-up and auto voltage configuration before the main supply stabilizes.

This is not user serviceable.

Hence my question if it is a conventional power supply, or a switching supply. A conventional supply completely switched off likely wouldn't have suffered any damage.

 

[agedhorse]

To be clear, a thermistor is not a fuse.

When subjected to stress beyond the design limits, unable to dissipate the excessive energy as you said, they fail. In this case, blowing implies opening the circuit. Better that than a short. Being where they are in the primary transformer circuit, it isn’t unusual that they fail when hit hard as is often seen with power line lightning strikes. Beyond their power up current limiting capacity, thermistors are used as added circuit protection devices.

They do not fail from the voltage but the excessive current combined with the voltage. Lightning strike by itself isn't the cause of the damage, it's the current that flows... which also damages other components. Often, you will find additional damage beyond the thermistor which must be addressed. Otherwise, upon power up, additional components )such as the primary bulk storage caps) can explode if they are compromised. This is a dangerous and messy event.

Thanks a lot for your advice!

Let me ask, if I find an identical thermistor, is there more to it than to remove the original one and solder in the replacement?

The limited current power supply you mention, what exactly is it?

I apologise for asking but I cannot simply go to a store and ask for something that I don't know exactly what it is supposed to do.

There are different kinds of limited current AC supplies, depending on the type of power supply. As this involves primary voltages, and a lack of understanding of the (real) dangers involved, I'm not comfortable going into detail that's likely to be misunderstood.

(Please note that I'm not being a jerk here, but it's quite possible to get injured. I have a special test bench/equipment that I use when working on switchmode power supplies for exactly this reason. I don't want to get hurt.)

 

[BadExample]

But there are many up sides too to living here

I completely get that! As well as the challenges that face you.

Looks like it has a switching power supply.

Being a micro-amp implies that, but the wide voltage range without any thing you change to use different line voltages mostly confirms it.

To me they are a lot more difficult to troubleshoot than a linear power supply. In part to inexperience, but you can't just take a few meter measurements and find what failed. The upswing is, switching power supplies have been used in TV's and computer monitors going back at least to the 1980's. I'm thinking a TV repair shop may be able to get the power supply up, then you can see if it will live again.

 

[agedhorse]

They ARE more difficult to troubleshoot, there are a lot of things going on operating in a non-linear mode... and they are potentially more dangerous due to the primary rectifier and bulk storage being located on the primary side of the isolation barrier.