Hifonic Hercules 4k

[megael9]

This amps have one shoulder that's getting hot, and the output have a high friquiency noise( no audio), I check most of the components of the driver board
And they looks ok, all audio MOSFETs are measuring ok. U2, u3 have no part number and I can not check them. can some one tell me where the audio MOSFETs gate reference ground is? And by the way when this amp came to me Q220 and Q213 were shortened.
Additional help will be appreciated
Thank you

 

[Perry Babin]

Post a photo of the face of the audio driver board and one showing the entire main board.

 

[megael9]

Here are the pictures

 

[Perry Babin]

U2 - TL072

U3 - LM211

The gates are driven from the positive rail down 10v or from the negative rail up 10v.

 

[megael9]

Second picture

 

[megael9]

So I need to use the rail voltage as a reference to read the audio gate signal?

 

[Perry Babin]

What are you using to read the drive signal (scope, multimeter...)?

 

[megael9]

Scope

 

[Perry Babin]

Connect a 10k resistor between pin 1 and pin 2 of the TL072. Drive a sine wave of ~100Hz into the amp. That should allow you to see audio out of the TL072 and into the LM211. The output of the LM211 should be a square wave. That square wave should also be seen at the output transistor gates (driving +/- from the rails).

 

[megael9]

I soldar a resistor from pins 1 and 2 of tl072, and no signal was present. I then de solder the 10k ohms resistor and all signal are present. I'm using the +- rails voltages as reference.

 

[Perry Babin]

Are the outputs still out of the amp?

 

[megael9]

No, they are out of the circuit.

 

[Perry Babin]

Generally, if there is no feedback (amp not fully functional), you won't get any audio out of the TL072. That's what the 10k resistor is for.

Without the resistor, did you get drive all of the way to the output transistors?

 

[megael9]

Yes, all the way to the transistors pads. Square 170hz.

 

[megael9]

Sorry I mistake, I soldered the 10k to u3 (lm211) not to tl072

 

[megael9]

All signals are present? But when I solder audio MOSFETs one shoulder is still getting hot.
Any suggestion? Or schematic?

 

[Perry Babin]

Are the signals the same for the FETs that are heating up?

If so, you may have a bad inductor.

 

[megael9]

One of the 4 signals ( pin 20) is side rolling , the other 3 are looking ok.

 

[Perry Babin]

Rolling? Do you mean that the scope isn't locking on? If so, adjust the trigger level.

 

[megael9]

Yeap, Adjusting the trigger locks the signal. ( no rolling)