Any Quad mavens out there? I have a 303 with one channel output not sitting midrail. It is about 44v (out of 67) hence is clipping early topside. Have replaced all electrolytics on the PCB and pulled all the small signal transistors and checked them with a Peak DCA75 and found no leakers or baddies. The offset trim won't dial it in. While I had all the small semis out, I powered the channel up off the bench PSU and it sat dead centre, so it is not the output devices or final drivers. Run out of ideas. Anyone?. Do the little compensation caps give trouble?.
M
M
Last edited by a moderator:
Have you referred to the service manuals and checked the simplified schematic diagram for the VAS bias of approx. 9V? The midpoint voltage is derived from a voltage reference at the VAS stage. If that is wrong, so is the midpoint.
This link is to the service data - free after registration:
Quad 303 - Manual - Stereo Power Amplifier - HiFi Engine
This link is to the service data - free after registration:
Quad 303 - Manual - Stereo Power Amplifier - HiFi Engine
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.