ARCAM Delta 120 fault find help required

paulrerrie

Member
2008-01-10 10:46 pm
Hi, after a mishap with a A/B selector box I'm trying to find a fault on my ARCAM Dela 120 MkII. No internal fuses blew.

I have replaced a small signal PNP transistor and some burnt resistors on both channels and now have audio. However I cannot measure any bias current across the 0.22 ohm resistors. I have removed and diode checked the driver transistors and they seem fine. The bias servo transistor only has approx 0.6V/-0.6V at E and C, even though schematic says it should be 1.1V/-1.1V (bias pot is at minimum).

This is a quasi-complimentary circuit using transistors for the output devices.

Any help appreciated.

Paul