3007 Loss of 24v supply in control.
Check that all the LED indicators are illuminated, situated in the lower panel behind the tape reader door. Check the 24 volt power supply (inside rear of the control) with a voltmeter. If 24 volts is present replace any faulty fuse. If there is no 24 volts present at the power supply, switch off the control, disconnect all outputs from the 24 volt supply and re-apply power to the control; recheck for 24 volts at the output. If there's no output, then the power supply is faulty, and replacement is required.
There may be a fused voltage regulator fitted in series with this power supply output. If so check the voltage either side of the regulator, and its fuse. It the regulator seems to be faulty it can be bypassed by linking its two wires together with an inline fuse holder.
Another cause for this error could be dry joints to resistors R6, R10, R14 or R58 on the WD50 Watchdog board.