BBC MASTER ---------- Fault: Not initialising Fix : Check IC43 pin 2 for 16MHz clock - If not working, check the crystal controlled oscillator circuit formed by half of IC43 and X2. NOTE: If the 16MHz clock is not operating then RAM RAS and CAS lines could be held low causing permanent damage to some / all DRAM's. Check 1, 2, 4, 8 MHz clocks on pins 4, 5, 6, 7 of IC42. Check 2MHz on the CPU clock input IC14 pin 37. Check RAS and CAS to the DRAMS (the RAS and CAS should be good 4MHz square waves). Check the multiplexed address lines into the DRAM's - IC17 and IC23 pins 6, 7, 8, 10, 11, 12, 13, 14. If any of the DRAM timing is out of spec, check Capacitor C26. Fault: Display works in all modes except 7 and 135. Fix : If cursor but no text / text fragmented check 6MHz to SAA5050. Fault: Lines of normal size appear cut in half. Fix : Check VSYNC at the CRTC IC22 pin 40. Fault: Real time clock loses data when powered off Fix : Battery flat FET transistor Q4 faulty. Fault: A/D convertor not working properly Fix : Check IC49 pin 2 for 1MHz clock Fault: CTRL BREAK behaves as BREAK Fix : On early MASTERs Capacitor C11 needs to be 100uF instead of 10uF, Diode D8 changed to 1N4001, Transistor Q3 should have a 1.8k resistor connected between base and emitter. Fault: Machine powers up with ACORN MOS ACORN ADFS but nothing else happens. Fix : Try typing CTRL F BREAK. If this is ok then connect a drive with an ADFS disc in it or type *CONFIGURE nodir