Hello: I saw this project and thought it was cool on repairing a malfunctioning CUBE IC What, I wondered, could possibly be causing the monitor to withhold the keyboard data blips? The very same monitor and keyboard would report them just fine on the working cube. I checked the +12v, -12v line and 20 Mhz clock signal to see if any of them were out of spec. And while the 20+ signal did look slightly lopsided, it was exactly the same on my working motherboard. Everything else seemed identical. Then it hit me. I powered down the system, pulled the motherboard out and grabbed my multimeter. With the meter set to ohms, I put one lead to the serial in pin and touched the other to ground. Sure enough, it showed continuity. The serial in line was being shorted! No wonder the monitor couldn't send data back to the machine, it was being pulled to ground! full project here
http://www.jax184.com/projects/NeXT/NeXT.html Best Regards Rob Blessin
Huh. That old problem again. So now that makes two with this problem.
Quote from: "pentium"Huh. That old problem again. So now that makes two with this problem.
it's cool how he traced down the problem and fixed it, I've seen this before as well so now there's a solution .
Yeah he did a pretty fantastic job. His writeups are nicely detailed as well. Shame he hasn't added anything in a while.