hairball 1176 rev d q bias problem

[Dr. Lessley]

hi there ,  I'm new to diy and have completed several preamps without any trouble at all. however, i recently built Hairball Audio's 1176 rev d. the build seemed to go well and everything looks really clean but, when i started the calibration process i got stuck on the q bias. everything is set up as its supposed to be with .775 at the input and 2.75 at the output. Ive turned the q bias all the way in both directions and it has no effect on  the output signal or the vu meter. Again, I'm new to this and have no idea where to start solo...any help would be much appreciated.

thanks in advanced

 

[Rocinante]

There is a thread located under dynamic processors that is dedicated to the hairball 1176 rev d. It is chock full of every answer one could ever hope for with regards to troubleshooting this project.  I am certain the answer you seek lies there.  Reading and searching through that thread worked tremendously well for me when I had problems with biasing the 1176 rev d.

 

[Dr. Lessley]

thank you so much for the reply...i will definitely check it out and see what i can come up with.

 

[RuudNL]

To start with, I would measure the voltage between the slider of the Q-bias pot and ground.
If you turn the trimpot, you should get a voltage variation on the slider.