Posts: 110
Threads: 24
Joined: Jan 1970
If there's actually some limit to the useful life of LCD
displays it must be quite high, indeed.
I have a number of very early LCD calculators in my
collection, some of them of the 'first-batches' yellow
LCD type, and not only do they still work fine, but I can't
notice any sign of degradation or diminished functionality
whatsoever, despite the fact of them being 25+ years old.
Posts: 298
Threads: 35
Joined: Jan 1970
I think LCD's are more prone to physical damage, e.g. temperature, shock, delamination etc. So if you look after them well they should last a long time.
LED displays seem more prone to electrical faults in the driving circuitry, I'd guess this is due to the much higher current being drawn. I don't know what the fail mechanism is for LED drivers, I'd guess burnout of the driving circuit or electromigration (over a very long time the internal wiring of the ic gets thin and eventually 'snaps' due to the high current density).
If you own an HP calc it doesn't matter what the fail mechanism is, it still stops working (both are repairable - replace the LED driver or replace the screen).
From this forum there seems (to me) to be more postings about LED problems than LCD - this would imply that 'well looked after' LCD calcs are more reliable than LED calcs but may also be due to LED calcs being older, or users just acepting that LCD's fail so are not too bothered about asking for help.
my 2 pennies worth
Posts: 1,788
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Some early LCD's had problems with contaminates in the goo that over time caused it to decompose. This does not seem to be a problem with HP LCD's. Early LEDs had problems in the bonding and processing of the gallium arsenide/phosphide/etc semiconductors. I have seen quite a few bad LED displays in HP calculators. The only LCD faults were caused by physical damage or dirty interconnects.
Posts: 331
Threads: 47
Joined: Oct 2005
I did some reliability testing of LCD displays in the early 80s. They will last for a very long time if they are stored and used at room temperature and with the humidity level not too high. High humidity can be a killer for early displays and so can any contaminants introduced in the manufacturing process. So dont store them outdoors in damp conditions.