r19?!?!!?

[ronny516]

having followed the newest assembly instructions while constructing a rev 1.6 c84. i took a guess that r19 was now what r33(as per the old instructions) was. i rotated r19 until my dmm said it was 0v, and yet the noise floor is still high, and when i tried rotating it back to check if the component would work and the voltage would raise, to my surprise it stayed at 0v?

so my question is what does r19 do, and what am i doing wrong?

thanks
ronny

[tpryan]

On rev 1.6, R19 is the 100 ohm pot close to U1. You must adjust R19 until the DC voltage between pins 1 and 7 of U1 is 0V. Once you do that, your other symptoms will likely disappear.

[ronny516]

On rev 1.6, R19 is the 100 ohm pot close to U1. You must adjust R19 until the DC voltage between pins 1 and 7 of U1 is 0V. Once you do that, your other symptoms will likely disappear.

After "clicking out" R19, I was only able to get U1 pins 1 and 7 to read 4.66V DC.

The loud clicking and noise floor remain.

I have also noticed that the op amp at U1 is running hot.

I exchanged U1 with U3 and found the results.

[tpryan]

Are you absolutely sure that R20 and R21 are 1K?