Re: An Enhanced MK14 (MK14E)
The 74L86 isn't pin compatible with the 7486 / 74LS86 - at least I'm fairly sure it isn't - so I guess you have rearranged the pinout in order to try this.
The theory about the use of the 74L86 was that it had been chosen intentionally due to its unusually slow propagation delay in order to make sure that things happened in a particular order. Maybe this is something which only affects character mode, we have never really looked into it. If you are having difficulty obtaining a char gen, forum member Realtime has a little daughterboard available which hardware emulates the original char gen and just plugs into the char gen socket.
If you are finding that a 74LS86 works OK then maybe that is something Tim or myself (or anyone else with an original or replica SOC VDU) should also try to see what happens, although the pinout of the 74LS would have to be rearranged into the right layout before fitting into an original VDU PCB.
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