Repairing LCD display on Keithley 580
Working on a Keithley 580 micro ohm meter that has a display problem. The
first row which controls the bottom segments is very faded - the more segments that are lit, the more faded they are. I've already used alcohol to clean the two zebra strips, PCB and LCD itself. I've tried re-orienting the zebra strips to see if the problem moves; it does not. Checked the UPD7225 driver chip - pin 17 (COM2) drives this row, it is working fine. I believe that either the LCD itself is defective, or perhaps the conductor on the glass is partially open/high resistance. If the latter (and I'm hoping this is the case) has anyone ever had this sort of problem, and perhaps tried one of those conductive pens to repair the fault? Thanks. |
Repairing LCD display on Keithley 580
JW wrote in message
... Working on a Keithley 580 micro ohm meter that has a display problem. The first row which controls the bottom segments is very faded - the more segments that are lit, the more faded they are. I've already used alcohol to clean the two zebra strips, PCB and LCD itself. I've tried re-orienting the zebra strips to see if the problem moves; it does not. Checked the UPD7225 driver chip - pin 17 (COM2) drives this row, it is working fine. I believe that either the LCD itself is defective, or perhaps the conductor on the glass is partially open/high resistance. If the latter (and I'm hoping this is the case) has anyone ever had this sort of problem, and perhaps tried one of those conductive pens to repair the fault? Thanks. How many backplanes does it use? ie comparing total number of segments and active pins. Discover which backplane controls that line , via 50Hz sig gen or similar and trace a problem on that line -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://diverse.4mg.com/index.htm |
Repairing LCD display on Keithley 580
On Wed, 5 May 2010 11:46:27 +0100 "N_Cook" wrote in
Message id: : JW wrote in message .. . Working on a Keithley 580 micro ohm meter that has a display problem. The first row which controls the bottom segments is very faded - the more segments that are lit, the more faded they are. I've already used alcohol to clean the two zebra strips, PCB and LCD itself. I've tried re-orienting the zebra strips to see if the problem moves; it does not. Checked the UPD7225 driver chip - pin 17 (COM2) drives this row, it is working fine. I believe that either the LCD itself is defective, or perhaps the conductor on the glass is partially open/high resistance. If the latter (and I'm hoping this is the case) has anyone ever had this sort of problem, and perhaps tried one of those conductive pens to repair the fault? Thanks. How many backplanes does it use? ie comparing total number of segments and active pins. Discover which backplane controls that line , via 50Hz sig gen or similar and trace a problem on that line Um, there is no problem on the signal, the signal is fine. I'm wondering if the traces on the LCD where the zebra strip connects can be repaired with a conductive paint, or whether I'll just make things worse by trying. |
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