VR Adjust Question on DSP Board

[GZinc]

Hi, I'd like some help please , What is this Vr1 adjusting? , its on page 4 of the schematic, marked with red arrow.

 

[Perry Babin]

Is that an integrator circuit that converts the square wave to a triangle waveform?

 

[GZinc]

im not sure, i did play with it but put it back how it was(roughly) i tried probing all 3 of its pins while turning it to see if anything changes, but nothing, posibly im not grounding the oscilloscope probe in the right place?

 

[Perry Babin]

What's the signal on pin 6 of U9?

 

[GZinc]

u9 Pin 6

 

[GZinc]

The amp is working, just want to make sure doesn't destroy itself later on and being from me playing around with that RV.

 

[Perry Babin]

I would think that the pot is to adjust the symmetry of the triangle waveform.

I think the waveform should be showing up perfectly horizontal. What if you connect the scope ground to the ground of pin 3?

 

[GZinc]

that was a challenge 🙂 indeed looks much even

 

[Perry Babin]

I don't know if you want to do any more with it since the amp is working but you could monitor the signal while adjusting the pot.

I'd expect the DC voltage on pin 6 to be very near 0v. Does the pot affect the DC offset?

 

[GZinc]

i held oscilloscope ground on pin 3 and probe on pin 6 of u9, and turning the knob from min to max changed the triangle voltage from 1.4 at minimum to 1.7v at max (clockwise). so i'll put it how it was (has a mark from factory) and leave it alone. If you would tell me how to check for dc offset , would be greatly appreciated .

 

[GZinc]

The dc voltage on pin 6 is dead on zero.

 

[Perry Babin]

I don't see any problems.

What was the amplitude of the triangle waveform at the factory setting?