Rockville DB comp5

[caraudioguy2100]

Does anyone know the value of these 2 resistors ? They are CGND,RGND

I’m not getting any input voltage to the regulators

 

[Perry Babin]

C is a resistor?

Rgnd and Cgnd are typically between the primary and secondary grounds. Is that true here?

 

[caraudioguy2100]

C is a resistor . At least it appears to be its badly burned and can’t make out what it is . Also I can’t get any reading on it at all off the board in either ohms setting or the capacitor setting on the meter

And yes they are between primary and secondary ground

 

[Perry Babin]

The photo is out of focus but you can see one example that may be similar below.

If nothing else, it's a good starting point.

 

[caraudioguy2100]

According to the schematic CGND is a 0.1uf cap
And RGND is a 1K cap .

Should I try that combo and see if it works ?

 

[Perry Babin]

Yes.

These aren't critical. The worst that should happen with them missing/defective is a loss of reference ground on the secondary.

 

[caraudioguy2100]

Replaced the cap and resistor.

I removed the regulators and the burned 10ohm resistors .

When testing for input voltage to the regulators I still get no voltage

 

[Perry Babin]

Are you placing the black probe on the ground pad of the regulator?

 

[caraudioguy2100]

Yes

 

[Perry Babin]

Do you see a square wave on the 10 ohm resistors?

 

[caraudioguy2100]

No .

And I also checked the power supply fets for drive signals .

I only get drive signals on half the power supply fets .

 

[Perry Babin]

Follow the drive from the driver board to the FETs to find the point where you lose signal.

 

[caraudioguy2100]

Ok I reflowed the solder on the driverboard to main board and got drive on all the fets .

I also see square waves on the 10 ohm resistors

 

[Perry Babin]

You should have input voltage now.

 

[caraudioguy2100]

Do the regulators need to be in circuit in order to get input voltage?

I placed the black probe on the ground pad for the regulator and checked for input voltage which I assume is rail voltage and get 0.68 volts I also checked both sides of the 10 ohm resistors and only get 0.68 volts on those as well

 

[Perry Babin]

The 10 ohm resistors have a square wave, not DC.

What is the amplitude of the square wave on the 10 ohm resistors?

 

[caraudioguy2100]

Ok now I have input voltage .

+ - 27 volts

Replaced the 10 ohm resistors and regulators .

When I power the amp up it just burns the 10 ohm resistors

 

[caraudioguy2100]

What would cause the 10 ohm resistors to burn instantly when the regulators are in circuit ?

 

[Perry Babin]

Do BOTH 10 ohm resistors burn every time?

Looking at the regulator input pads, do you have clean DC?

 

[caraudioguy2100]

Both resistors burn .