27
（
1
）
Check if the connector of drawer fits the definition of SENOR standard drawer connector;
（
2
）
Check if the 6pin crystal connector becomes oxidized or dirty
（
3
）
Check if the 6pin socket becomes oxidized , dirty or out of shape;
（
4
）
Check if the fourth drawer connector is under AC 20V;
（
5
）
Check if the big cable between the communication board and the mainboard looses or drops;
（
6
）
It may be the problem of communication board or circuit abnormalities of mainboard. Please
change a new communication board for testing, if it still doesn’t work, change a new mainboard
for testing again.
