buffer full of data is printed.
3.3 If the problem does occur, look at the wiring of the RS-232 lead on the end that connects to the printer, and check that a lead exists, connected
from pin 4 to pin 20.
4. SER OUTPUTS
4.1 There is one potential fault with the SER outputs from the QL that is not obvious to find.
4.2 If either pin 1 (ground) or pin 6 (+12V) is not properly connected (e.g. lead not soldered to pcb), on either SER1 or SER2, the port may work,
although any device that draws power from the QL, (e.g. a serial-to-parallel converter) would not operate.
4.3 Apart from checking visually, one test would be to connect pins 1 and 6 externally and check that 15 mA to 20 mA of current flows.
5. HOW TO CURE A CRASHING QL
5.1 You may have a QL that "freezes" after a few hours of operation. We do not yet fully understand why this happens with some computers.
5.2 To cure the problem, take out all the ICs that plug into sockets, in the main pcb. Using some proprietary cleaning fluid, clean the legs of the ICs,
and the sockets; then replace the ICs. In most instances, this cures the fault.
6. FLICKERING DISPLAYS
6.1 Run the following program to demonstrate an annoying screen flicker.
10 BLOCK 40,40,40,40,20
20 GO TO 10
This is common to all QLs, and all versions of ROM.
6.2 You can also see the effect if you move window 0 to put the cursor near the top left-hand corner of the screen. In this position the cursor has not
had time to refresh itself before the screen refresh reaches it.
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