Troubleshooting a recently build AMP6-BASIC

[OscarRM]

Hi,

I've just finished building the kit and I haven't connected it yet to speakers so in fact I don't really know if it does sound or not. However, the amp shows a couple of weird behaviours:

- Idle input voltage at one output is around 46 mV while the other one is around 86 mV
- VREF is around 1.04 volts (pin4 of the chip to ground), lower than expected. The weirdest thing is that if I probe VREF while the amp is not connected to an input (but connected to power) after probing it the VREF goes to 0 and the speaker outputs voltage goes to 12V (power supply voltage). This doesn't seem to happen if the amp is connected to an input, keeping VREF stable at 1.04V.

Is anything clearly wrong? Is it safe to plug some speakers? I wouldn't like to blew them up.

Thanks in advance,

Oscar

PS: My electronics knowledge is pretty limited.

[FFF]

Please read:
- Definitely read TroubleShooting under Technical-Info, Building-Kits. thoroughly
- Similar Threads (bottom, left)

[OscarRM]

Thanks for the answer FFF.

The 12Volts at the output seem to be a problem. After reading the TroubleShooting again it looked to me like there could be a problem at the input bias. I checked the Voltage and is around 2.35V so it seems to be correct. This voltage is the same whenever the output voltage is 12V or is less than 100mV. Everytime I probe pin #4 in the chip (VREF) the outputs go to 12Volts and seem to stay there.

I'll keep reading threads to see if I can find something but if somebody has any idea please let me know.

[OscarRM]

Oh, oh. I was probing the chip pins with the multimeter and I got a spark. After the spark things look much worse:

- Pin #4 to ground gives 4.84 V. This looks very bad.
- Output voltages while idle went lower: 4 and 20 mV.

[Saturnus]

LOL

You should never power up a bridge-tied load amp without the load connected, amp6 is no exception.

[OscarRM]

Aha...

So Saturnus, you mean I shouldn't have powered up the amp without speakers?

Bear with me, as I said my electronics knowledge is very limited.