Hallo William, > Check the PLA at U17, the 74LS237 address multiplexers at U13 and U25, > and the 74LS258 multiplexer at U14. The 74LS237 at U25 is the most > likely. I presume you mean the 74LS257s. Anyway they will be the first ones to be exchanged (some day) and if it proofs one of them is the troubleshooter then I still don't have a good explanation for this behaviour. A 257 is nothing more than a couple of switches. So I expect a "nice" address like 1, 3, 7, 15 etc bytes free. 192 doesn't fit in this scheme. The only ICs I did not exchange yet are all the 74s and the colour-RAM. (Geoffrey: if no reasonable explanation then the PLA is in 99% the first one to be exchanged in my experience) The last one cannot be the troubleshooter and the same way of logica also applies to these 74s: this "weird" address doesn't fit in the these 74s normally behave. Groetjes, your puzzled Ruud - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail firstname.lastname@example.org.
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