Problem with HCA-2

[jrhymeammo]

Hey guys,

I've recently sold my HCA-2 amplifier to a gentleman in UK, and he's experiencing a problem.

Here is what he wrote in his Email.


The amp arrived but there's a big problem.
>
> Do you know if the protective fuse installed in the back of
> the amp is the right
> one? Also, you mentioned that the amp is in perfect working
> condition and I
> believe you for that.
>
> But a very strange thing happened - I'm aware that the
> speakers must be
> connected before plugging the amp on.
>
> Actually, I'm using a step-down transformer as most of
> my equipments are U.S.
> voltage. This transformer has a power switch.
>
> My wall power outlet also has a switch. I attach the
> speakers, then I plug-in
> the power cable you gave me. I switch the wall power outlet
> on but I haven't
> switch the STEP-DOWN transformer on yet.
>
> All of a sudden I heard a loud cracking noise and saw a bit
> of smoke coming from
> the amp.
>
> What made me puzzled is that the STEP-DOWN transformer
> switch is still OFF which
> means that there's NO current running thru the amp, so
> why will it blew-up?

Here is a picture of a piece that blew up.






It does not look like he should trying turning his amp on, but does anyone know why this unit blew up the way it did? I imagined that fuse would go out first before other components, but fuse remained intact. He will need to get it serviced regardless, but would love to offer him any advice that will be helpful.

Thanks for your help,
JRA

[Feanor]

Hey guys,

I've recently sold my HCA-2 amplifier to a gentleman in UK, and he's experiencing a problem.

Here is what he wrote in his Email.


The amp arrived but there's a big problem.
>
> Do you know if the protective fuse installed in the back of
> the amp is the right
> one? Also, you mentioned that the amp is in perfect working
> condition and I
> believe you for that.
>
> But a very strange thing happened - I'm aware that the
> speakers must be
> connected before plugging the amp on.
>
> Actually, I'm using a step-down transformer as most of
> my equipments are U.S.
> voltage. This transformer has a power switch.
>
> My wall power outlet also has a switch. I attach the
> speakers, then I plug-in
> the power cable you gave me. I switch the wall power outlet
> on but I haven't
> switch the STEP-DOWN transformer on yet.
>
> All of a sudden I heard a loud cracking noise and saw a bit
> of smoke coming from
> the amp.
>
> What made me puzzled is that the STEP-DOWN transformer
> switch is still OFF which
> means that there's NO current running thru the amp, so
> why will it blew-up?

Here is a picture of a piece that blew up.
...


It does not look like he should trying turning his amp on, but does anyone know why this unit blew up the way it did? I imagined that fuse would go out first before other components, but fuse remained intact. He will need to get it serviced regardless, but would love to offer him any advice that will be helpful.

Thanks for your help,
JRA

It's pretty clear that current was getting to the amp despite the step-down being turned off. What's likely too that the current getting throught was 220V (or 240V, whatever it is in the UK). This being the case there is nothing strange about the amp is having problems -- I wonder if it's only the fuse?

One can feel sympathy for your buyer but it does seem likely that the problems is his and no fault of yours.

[bfalls]

The failed component looks like a varistor, a protective component used to shunt current away from a protected circuit. There definitely was current present. I'm also surprised the fuse didn't go first. Hopefully, it did it's job and all will be functional after the component is replaced.

[Rich-n-Texas]

Maybe the fuse is only protecting one leg of the AC voltage (the "hot" side), and current was produced in the neutral side via reverse polarity. I would be suspicious of the step-down transformer.

The fried component looks more like a ceramic capacitor (maybe a filter cap) to me.

Whatever the case, it hurts to look at that picture.

[jrhymeammo]

He's currently checking the fuse.

I have not experience with Step-down Convertor, but doesn't one have to turn on a transformer on, before turning on a Electronic unit?

I just hate seeing another audio hobbist getting hurt like this.

JRA

[Rich-n-Texas]

Is this transformer a multiple outlet type? If so, has he ever plugged anything else into that particular outlet previously? If it's a single or dual outlet type, is there a power strip/conditioner in the path?

A tip for him: Don't plug a step-down transformer into a switched outlet. The load can heat up the switch's contacts and you don't want heat sources behind walls.

[jrhymeammo]

I've asked him is his transformer could be faulty, but that is not the case.

Wall outlet=>Step-Down Tranny=>Audio Gear is how he has it setup.
Tranny seems to be working fine.


He didnt even turn on his amp or Step-down Tranny, just plugged it in. I understand that components still suck in some juice, even if units are not powered on. I'm no Electric Engineer by a long shot, but if this is a common result, then it kinda scare me. I'm glad he had amp cover on, cuz a piece blew off and banged around inside.

Could a digital amp act differently than normal transistor amp?

He's looking to ge it repaired in either US or UK.

Thanks to Feanor and Rich for your inputs.
J

[Feanor]

I've asked him is his transformer could be faulty, but that is not the case.

Wall outlet=>Step-Down Tranny=>Audio Gear is how he has it setup.
Tranny seems to be working fine.


He didnt even turn on his amp or Step-down Tranny, just plugged it in. I understand that components still suck in some juice, even if units are not powered on. I'm no Electric Engineer by a long shot, but if this is a common result, then it kinda scare me. I'm glad he had amp cover on, cuz a piece blew off and banged around inside.

Could a digital amp act differently than normal transistor amp?

He's looking to ge it repaired in either US or UK.

Thanks to Feanor and Rich for your inputs.
J

And you believe him that his transformer is working fine? OK, maybe it is if it is turned on -- which it wasn't. Your buyer was counting on it passing not current when is turned off, but it did and it seems 220 volts. It wasn't the fault of the amp nor does it being a switching type have anything to do with it. The problem was a poorly designed transformer.

You may feel sorry for him but there is no need to feel guilty or accept any responsibility.

[Rich-n-Texas]

Let's back up a couple of steps JRA. First, how do you know the picture (which I assume he e-mailed you) is of the amp you sold him? Why don't you ask him to send a picture of the transformer he used. A step-down transformer is essentially nothing more than two coils with one coil having more wire windings than the other.

If he has everything plugged into the transformer that obviously means it's a multiple outlet type.

I still believe the possibility exists for a short to have occured in the transformer that put an AC potential at the recepticle that he plugged the amp into.

In any event, if he asks you to send money, I'd be very suspicious.

[jrhymeammo]

Thanks guys.

He is not indicating that I sent him a faulty amp. Also, not requesting for a refund of any sort. This post transaction is not getting ugly by any means. I'm not worry about that.

Just real unfortunate for a good guy.
Thanks again,