Reverse engineering a phono pre, help these old eyes

[dano12]

I've spent the last two days reverse-engineering a low-cost commercial phono pre. I've been as diligent as I can in getting it right, but after many hours my eyes are going crossed. Anyone have some free bandwidth to see if I'm on the right track?

Here's the schematic I have so far, does it look remotely like a discrete phono pre? I can't figure out why there is no DC supply to the collector of Q1...





Doh, I guess it would be helpful for me to include the photo of the PCB with the parts legend. Here's the link because it is a rather large file:

http://www.beavishifi.com/ComPhono_PCB.png

[alayn91]

Hello,

According to the PCB picture, you have forgotten R12, 270KR, from Vdc+ to Collector of Q1 and base of Q2.

Regards.
Alain.

[dano12]

Originally Posted by alayn91

Hello,

According to the PCB picture, you have forgotten R12, 270KR, from Vdc+ to Collector of Q1 and base of Q2.

Regards.
Alain.

Thanks very much for the good catch. I've updated the schematic--it is looking more like a valid circuit now.