I know nothing about the architecture of whatever controller is on your machine, but changing line transmitters/receivers (1488, 1489) and a programmable I/O chip (8255a) is not likely to have much to do with booting... but (in fact) it did. Your best bet is to buy spare circuit boards on ebay and swap boards until you correct the problem.
That was the quick answer. The longer answer starts with the error message. If you believe the error message, that there is a bad ROM (EPROM?), then you have to figure which one it is and replace it (unfortunately, you have to program it first, so see the quick answer). However, it is unlikely that the error message is completely telling the truth. Since you were able to change the machine's behavior by randomly changing out integrated circuits (how did you determine which ones to change?), perhaps something else is the problem. I would start over: check your power supply voltages and grounds, disconnect and reconnect all your connectors (clean the contacts where possible), re-seat all the IC's that are in sockets, etc. Things that vibrate, flex and corrode are your enemy. I congratulate you on already doing some of that, which is perhaps what changed the boot behavior.
And last thing: theoretically, EPROMs do not last forever. The 1's and 0's are stored as charge on the isolated gate of a transistor, which is basically a capacitor. Capacitors leak. I ran across a post in an antique musical instrument forum where someone recommended "refreshing" (reprogramming) eproms after 40 years to top off the capacitors so that they last another 40 years. The problem is, that you have to do so before they go bad, so see the quick answer. I wonder if anyone on this forum has experience with this phenomenon. Should be keeping copies of the eproms on my own 40 year old machine?
