[time-nuts] 2100f lcd display
cfharris at erols.com
Tue Apr 26 15:55:18 EDT 2005
Don't believe the Austron manuals and schematics when it comes to parts.
The 2100T/F is a mish-mash of 74C, 74LS, 74HCT, and 74HC parts. It appears
as though they picked the family to change the delay time specs, and fix
> I didn't have the guts to pry out the large lcd display on the austron
> 2100. But I now realize the problem with its display.
> Whats happening is noise from the ttl logic is falsely gating the cmos
> lcd drivers. This is a common engineering mistake when interfacing ttl
> to cmos logic. The recommended fix is to use an HCT part (74HCT240) as
> a bridge between logic types. Also I believe pullup resistors were
> another recomendation for interfacing ttl to cmos.
> Anyway I will keep the net advised as I eliminate noise in the austron
> 2100 display.
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