PArasound HALO A23+ repair

[yuriy326]

I have A23+ for around 3 years, and it was good.
Yes, I did contact the dealer (NAE) and Parasound. It looks like I wasted my time for three weeks. They respond, but it doesn't help. The last message from Parasaund was that my purchase wasn't legitimate!!!!
The amplifier protection circuit turns off the power after 10-20 min of operation. I disconnected the speaker, and it's still the same. Overheat protection newer comes on, and it doesn't feel hot. I'm using a balanced input to provide the signal. If the cable disconnected from the input, it looks like it works. At least it was on for 30+ minutes.
Does anybody have an idea or a schematic to go through?

 

[Doodski]

I never found a schematic. Do you have a DC voltmeter that can be used to meter the left and right speaker terminals when the fault is occurring and when it is not occurring. A normally operating amplifier will have some DC millivolts at the speaker terminals. Put the meter on DC volts and set it to 200 V DC for the first measurement and if there is very little DC voltage at the speaker terminals then you can use the 200 millivolt DC scale on the DC Volts meter. Post your results here and we'll see if there is anything obvious happening at the speaker terminals. This is a sophisticated expensive amp and it will be best if you can find a technician to repair it.

 

[yuriy326]

Hi Dodski, thank you for your quick response.
No signal in. right -0.4mV left -2.4mV.
After the power cycle, the amplifier is in fail mode. The power button has dimmed blue light, which never changed to red and then bright blue after pushing the power button a second time, and the channel blue light doesn't come on. The voltage on the speaker's terminal fluctuated, the right channel from -50mV to -0.9mV. The left from -20mV to almost -0.0

 

[yuriy326]

I remeasured in failed mode and both channels go to 0.0mV. it looked like a capacitor discharge happened.

 

[Doodski]

Hi Dodski, thank you for your quick response.
No signal in. right -0.4mV left -2.4mV.
After the power cycle, the amplifier is in fail mode. The power button has dimmed blue light, which never changed to red and then bright blue after pushing the power button a second time, and the channel blue light doesn't come on. The voltage on the speaker's terminal fluctuated, the right channel from -50mV to -0.9mV. The left from -20mV to almost -0.0

I'm not familiar with the LED colors and codes but it seems the unit is in protection mode and the relays may not be engaged so the speaker terminal voltage is near zero. ~50mV DC is not abnormal for a voltage at the speaker terminals. 0.0mV DC is abnormal as that requires perfect offset or a failed amp. Due to the nature of the fault and the sophistication of the amp I am going to recommend you send it in for repair service. If you like you can check the 4 fuses that are located on the main printed circuit board.

 

[yuriy326]

It looks like the power issue. All 8 capacitors have evidence of extended pressure from inside. Something triggered current protection. The question is, what? Replacing capacitors will not fix it. This is the reaction to something else. I hope this isn't the toroid.

 

[martin900]

What is the measured DC voltage on the main caps? If its close to (or over) rated and the amp runs hot, they might fail quickly.
I'd suggest to let a tech look at it, the circuit doesn't look complicated and someone with experience should sort it out with ease.

I also like to 'cheat' when diagnosing electronics - IR camera module on my phone shows what's getting hot when it shouldn't

 

[Doodski]

It looks like the power issue. All 8 capacitors have evidence of extended pressure from inside. Something triggered current protection. The question is, what? Replacing capacitors will not fix it. This is the reaction to something else. I hope this isn't the toroid.

Can you please post images of the caps bursting.