DD Z1a damaged

[Perry Babin]

I don't know what was causing the noise.

The outputs swing from rail to rail and the varying pulse width determines whether the output is positive or negative.

 

[Achim1409]

i think i found the problem. Bad solder from the Rail Bar.... The rail is moving inside that solder connection.

 

[Achim1409]

found on that driver board two broken driver and one diode. Can i use that diode es1g for the x3 62? How i can check u6,u4 and u3?

 

[Perry Babin]

Are you just finding these problems on the audio driver board?

 

[Achim1409]

yes. I have dismounted that board aggain to check.

 

[Perry Babin]

The X3 diode is used to produce the high-side supply. IT's likely that that driver IC could not have functioned without it being OK.

The TL072 and the LM211 ware already checked when you connected the 10k resistor and checked the signal up to pin 1 of the driver ICs.

 

[Achim1409]

yes, but after i took out the fets today, and gave power on it, it came smoke from the driver board. This is the reason why i have checked aggain. Also only to beshure that i dont made a mistake. Also i found broken soldering from the rail bar. Maybe that was the reason it blows after 30 minutes.

 

[Achim1409]

So, i have repaired the drive board, and put only one fet per bank from the good one i still have. The Noise is still there, but the frequency drops and then disapears. If i move a little bit the plug for B+, it starts again. MEasured on my Batterie only 11,4V. Also what is strange, if the noise is there, the Amplitude on the Fets start moving from left to right a little bit. If the Noise stops, there is no more movement. I understand, that the movement is because it producing Audio in that moment. But normaly it shouldnt produce any noise when the power is low. Maybe there is something with the power supply? Or is the noise transfered from the other Amp, from which i took the low voltage?

 

[Perry Babin]

Try using the winding (as suggested) on the transformer of your amp (not a second amp).

 

[Achim1409]

Its completely full of Silicon and glue... Ok, i will try tomorrow

 

[Perry Babin]

Use a very small screwdriver or similar object (careful not to hit any windings) to push a heavy fishing line through the silicone and use the fishing line to cut through the silicone.

 

[Achim1409]

Ok, i round the wire on a transformer on this amp. Still the same. Very Noisy with high frequencys.

Above two pictures. One is from High and Low side Gate Resistors. The other from the same high and low side on gate and drain.
Can you see anything on that pictures which explain that sound?

 

[Perry Babin]

You can't see audio at 20us. You should disable the driver ICs and see if the noise is present on the output of the TL072 on the driver board. You may not be able to see it. You may have to use an audio type signal tracer.

Would the noise be audible through a subwoofer mounted in the trunk of a vehicle?

What type of test speakers are you using?

 

[Achim1409]

Iam using a 2Ohm midrange 16,5cm speaker. I dont have a signal trace, but i will try with my oscilloscope. For sure the Noise will be audible with an sub. I tested many of digital amps with normal speaker, and this sounds not normal.

 

[Perry Babin]

Does it sound like this?
http://www.bcae1.com/temp/cooleditmixedoscillator01.wav

 

[Achim1409]

No, it sounds different. I will try to make an audiofile.
ABove two pictures with disabled Audiosection. Measured on Pin1 TL072

 

[Achim1409]

Sounds like an old modem.

 

[Perry Babin]

You'll have to be able to listen to any noise that you see to be able to trace it.

Without being there in person, an audio file will not likely be helpful.

 

[Achim1409]

Ok, so i expect, that it have to do with some of the TL072 or LM on the drive board. Because the noise is still there when the Preamp is disconnected. There is also no noise with disabled Audio drivers.

 

[Achim1409]

How much should be the level on Pin 1 of TL072 with no Audio injected? I have about 8VDC

Pin1 8V
Pin2 10V
Pin3 8V