Information from Jeff
Message 1
Dave, Update on Space City. I got the mpu working. The problem was in the reset circuit. So, all 4 proms are good and working, no need to verify. I still do not have a manual or schematics, but as soon as I get them I will let you know. I am VERY excited about having a working Space City! FYI: when the 8060 cpu first gets power, before the cpu comes out of rest hold, it displays the two decimals that I described earlier, then after a valid rest signal on pin 7 of 8060 it pauses... ( I think the 8060 is strobing in data from the prom at this time) then it boots and displays 78.XXX and high score 2.XXX.XXX. I will get the exact #,s for you when I have done more testing. There is a micro relay on the board that unshorts a RC pull up, then triggers a Schmitt trigger inverter to drive pin 7 of 8060 high and into a "run " state. I hope this tid bit of info helps you or someone sometime with a Zac pin of this vintage; they are well built pins and would be a shame for any to end up in a landfill cause of a small circuit problem.
Message 2
Dave, this is what I know so far. ------------------- 8060 mpu info: ac input connector: 1/connettore-a AC voltage readings from left to right, ground ref. on the bottom of R? 100 ohm 1/4 watt resistor close to mount hole in center of board. Also same ground buss the battery is connected to. 12/12/0/4.4/4.4/11.3/11.3/22.5/22.5/44/44 green/green/black/red/red/violet/violet/white/white/orange/orange Boot sequence: 39 ohm resistor ( R137) is released from ground through micro relay = power on. A RC circuit pulls reset line high(+5) to reset both ram and 8060 gets high on pin 7 = run .... through ic11 inverter driver in =1to 2 then 3 to output =4 About 4 seconds after 8060 gets high on pin 7 all pop bumpers flash on/ off rhythmically ( attract mode) and the display switches from ( recent score? )= .101.010 to (high score) 2.1.d0.800 But, now after a bit of testing the recent score and high score values have changed from what I originally seen when the mpu booted the first time. The latest development, after accessing the audits in test mode once. Now the mpu will only display F's in all segments , flashing like it is trying to display recent score and high score. The cycle is aprox. 8 sec. Attached, please find two photos showing the 8060 mpu and MY reset hack witch is to pull the end of R137 from circuit and ground to buss ground. Then a few seconds after switching the power on, I lift the ground from the end of R137 just like the relay would normally do. I still have a problem with the relay part of the reset circuit; but I am waiting on manual and schematics to arrive before continuing repairs. Hope you find this info useful and it helps someone somewhere save a Zac pin from the land fill. I can try to answer specific questions you have... and will certainly share any info/ docs. I receive when I get them. I am putting together an old PC to run a PC-10 eprom reader / tester to get the software documented.
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| 0212 & 0213 = mpu and reset hack; also shows -5, 12 and 5 volt buss |
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| 0212 & 0213 = mpu and reset hack; also shows -5, 12 and 5 volt buss |
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| Img_0215 = what display looks like before reset. |
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| img_0216 = after boot, high score attract mode. |
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| img_0218 = after boot, recent score attract mode. |