Display
Thanks to having access to several units, I was able to verify that the faults in the Display (lack of information, areas with low intensity, etc.) were often not due to the LCD, but to the control ICs.
This is important to note because several of the computers I examined had damaged the LCD and/or the elastomeric connectors due to improper handling. I assume that someone tried to increase the pressure between the PCB and the LCD, trying to solve the problem, when in fact the problem was in the control ICs.
DISASSEMBLY:
REPAIR:
As I mentioned above, it is easy for the ICs to be damaged, especially if they have been improperly handled. They are CMOS technology, very sensitive.
HLCD0538P: Controls the information bottom line.
HLCD0539P (x2): Control the 64 squares of the board. One controls rows 1 to 4, the other rows 5 to 8.
Testing several control boards with an LCD in good condition: None of the control boards worked properly.
Desoldered ICs to be tested separately.
Preparing a PCB as a test platform.
Installation of sockets for easy exchange of ICs.
Testing the ICs one by one.
All of these ICs have some kind of failure.
LCD BACKLIGHTING:
Original bulbs: Type "T1" of 3mm diameter, and 5V/0,2W.
Optional 6V/0,3W can be used.
ASSEMBLY:
It is important to clean the copper contacts of the PCB with alcohol.
Do not use alcohol to clean the elastomeric connectors. Good quality adhesive tape, for example, can be used to remove dirt.
The 6 fibre washers, which prevent excessive pressure on the elastomeric connectors, must be replaced.
