blow transformer

[ricrado]

HI everyone;

I new on this and I am going crazy.
i made a gainclone .It sound ok very nice no hum at all.
but everytime i put it on the transformer get very hot eveen with no sound at all.
I blew two of them in .
any suggestion.
i look at the boards and I do not see anything in short cut.The last time I take and amperimeter
and it was going up until 4.5 amp.
we use here 110v.
any ideas?
thanks ricardo

[Netlist]

Ricardo,

I think your amp is oscillating. You need a scope to check.
How big (VA) is your transformer?

/Hugo

[ricrado]

what do you mean sscilating"
And what is doing this?

The transformer is 20+20 .
The rare thing is that the sound is good and there is no Humm.
do you think it can be a bad chip?
ricardo

[Netlist]

In simple terms, an oscillating amp is producing high frequencies that you cannot hear.
If it puts much of his energy in doing that, a lot of current is running all the time even when no music plays.
A common cause is too long wires in the signal path or a bad board layout. Can you post a schematic and a picture of your amp?

If it plays fine, the chip will be fine, too.

/Hugo

[pinkmouse]

I'm with Hugo, definitely sounds like oscillation. What is the current rating of your transformer?

[runebivrin]

Well, if the chip doesn't get warm, it's probably not oscillating. Could just as well be an incorrect rectifier connection.

[Netlist]

Indeed, that is why a picture, showing the heatsink size could be handy. They could be massive.

/Hugo

[pinkmouse]

Whenever I wired up a rectifier incorrectly, the failure was usually instantaneous.

[BWRX]

I had a similar instance once and believe it or not a power supply capacitor was bad and measured a low impedance. The amp worked and sounded ok but the rail voltage was low and the supply got very hot because the bad cap was a low impedance across the supply rail.

[pinkmouse]

Yup, never happened to me, but that certainly sounds possible. Of course, it could also be a reversed electrolytic...