K8060 - TIP147 burned

Hello,

I built the Velleman K8060 kit.

Everything has been checked several times, the direction of the components, their value, the voltages of the transformer, etc.

Everything is in order.

The bias of RV1 has been set to 10.2mv (tested with a voltmeter).

The speaker is 8 ohms and was plugged in the right side.

The audio source is an mp3 player, which works great on another amplifier.

As soon as I sent sound (at a low level) to the input of the IN and GND terminals (connected in the right direction), the TIP147 transistor immediately smoked and burned.

The radiator is properly isolated from the two transistors. Nothing touches. The thermal paste is in place. I have already made many other montages, without any problems.
I do not understand why.

Attached photos:

Thank you very much for helping me understand what happened!

Dear,

It is difficult for us to solve this at distance, without being able to thoroughly inspect everything.
I hereby propose to return the product back to us, to the following address:

Attn Tech. Dep.
Velleman NV.
Legen Heirweg 33
9890 Gavere
BE Belgium

Regards,
Velleman Support

I approached my dealer, who offered to return the circuit to him. He can return it to you for analysis.
Thank you!

I had the same problem, solved by getting some genuine replacement transistors and replacing those protection and output transistors.

This happened to me as well. I was extra careful placing the components right, and even checked every resistor and capacitor with multimeter for correct values. Soldering was as well done carefully, so no cold joints or bridges. I replaced the original thermal paste with MX-4, which is non-conductive so that should not be the problem.

First powering up the amp everything looked well, the led light up, it was sitting idle no problem and I adjusted the bias to a bit over 10 mV. Connected a speaker (4 Ohm) and tried to play some music. First I had no sound, then it started to make a powerful maybe 50 Hz sound and in a few seconds the TIP147 went up in flames. On closer inspection the 47-Ohm R6 has some discoloration as well, so it has also suffered heat damage.

I am now rather wary of putting this thing inside an enclosure and into use, even if replacing components would fix this issue. I wish not to burn a house down… In reddit there is also a similar story about this exact same kit, where the 147 catch fire.

That said, the problem is interesting and I would love to find out why this happened even though it even has overload protection…