Hi, Is there anyone with a good set of 8/e prints who could help me narrow down some troubles?
My 8/e was working a few years ago, but now it's developed some problems. It seemed to work fine for about the first 2 minutes that I tried it, but then it developed these two symptoms: - Most of the time, upon power up, LOAD-ADDR clears all the random address lamps, but will not take an address, just all 0s. Occasionally when I power it up, LOAD-ADDR will permit me to load an address, and see it's contents as it should. I can then enter other addresses, hit LOAD-ADDR, and get consistent results looking around at random data in different memory addresses. - Regardless of whether it's in the broken load-addr state above or not, hitting DEP or EXAM just turns on the RUN lamp, and it's then stuck with RUN on, and non-responsive to any other front panel actions. This happens irrespective of the position of HALT. I then power-cycle it and it is back in either broken or working LOAD-ADDR mode as described above, usually broken. So far, the only M8330 prints I have found are extremely fuzzy, so I cannot make out the IC identifiers or match them up to the equally fuzzy schematic. By board-inspection I identified the 74S74 "run" flip-flop, and in fact I can un-stick the RUN state by briefly grounding CLR, but still cannot DEP or EXAM from the front panel -- it gets stuck back with RUN on if I hit either DEP or EXAM again. The power supply voltages are right-on. I've reseated and repositioned the boards. The connectors are very clean. Wiggling boards doesn't change any of the symptoms. Wiggling switches doesn't affect anything. This is a very clean 8/e. Mark -- Mark G. Thomas ([email protected]), KC3DRE
