Old Computers
Veteran Member
I recently purchased a piece of equipment called Heathkit Octoport. It is serial switch box that is software controlled and configurable. You send commands to it to link a serial port to another serial port, or link to one of the two parallel ports for printing.
When I purchased it, the previous owner said that it had some battery corrosion inside that had been cleaned, but it functioned before. I am not sure if the corrosion occurred before or after it had been put away.
When I received the unit I followed the instructions and I could get no response from the unit. I had originally used a straight through cable but then I realized that I needed a null modem. So I built the cable according to the diagram in the manual and all that I got was a junk character upon power on and power off. The characters tended to be |, }, and character that looked like the home plate in baseball. I was using the terminal emulator supplied with the kit to check this.
The first time that I did for troubleshooting was inspect the board for damage from corrosion. Aside from dulling the solder connections nothing seemed amiss, but I still went ahead and used some vinegar and distilled water to clean some suspect areas from corrosion. I also reseated all of the chips in their sockets to no avail. I then re-soldered all the solder joints that looked suspect, that did not help. As far as I can tell all of the voltages are in tolerance, and the clock signal is reaching the chips that need it (this board is powered by a Z80 and several support chips), but the square wave was not very square according to my 'scope (but that could be because I didn't compensate the probe). I also checked the halt line of the Z80 and it might have been high, based on the rudimentary check with the 'scope, but I don't want to conclude that it was high yet.
I have also managed to obtain a working unit so I can compare the two as well.
Does anybody have any suggestions for troubleshooting or any ideas for what could be wrong?
When I purchased it, the previous owner said that it had some battery corrosion inside that had been cleaned, but it functioned before. I am not sure if the corrosion occurred before or after it had been put away.
When I received the unit I followed the instructions and I could get no response from the unit. I had originally used a straight through cable but then I realized that I needed a null modem. So I built the cable according to the diagram in the manual and all that I got was a junk character upon power on and power off. The characters tended to be |, }, and character that looked like the home plate in baseball. I was using the terminal emulator supplied with the kit to check this.
The first time that I did for troubleshooting was inspect the board for damage from corrosion. Aside from dulling the solder connections nothing seemed amiss, but I still went ahead and used some vinegar and distilled water to clean some suspect areas from corrosion. I also reseated all of the chips in their sockets to no avail. I then re-soldered all the solder joints that looked suspect, that did not help. As far as I can tell all of the voltages are in tolerance, and the clock signal is reaching the chips that need it (this board is powered by a Z80 and several support chips), but the square wave was not very square according to my 'scope (but that could be because I didn't compensate the probe). I also checked the halt line of the Z80 and it might have been high, based on the rudimentary check with the 'scope, but I don't want to conclude that it was high yet.
I have also managed to obtain a working unit so I can compare the two as well.
Does anybody have any suggestions for troubleshooting or any ideas for what could be wrong?