HP97 The journey begins

[teenix]

Hi all,

I installed the motor driver hardware onto the CPU board and connected the motor up.

The motor and printer HOME wire connections were a bit of a challenge because the original wiring is not soldered. It is used with small receptacles so that the wires can be removed and installed easily and allow separation of the two circuit boards. I managed to find some modern replacements though, so hopefully ok.

I cannot test the printer in its native environment because the original CPU board had failed. I was trying to repair this for someone, but the ACT had failed, and I found some bad RAM. This is what led to the 19C CPU replacement project which is now starting to come to life.

I plugged the motor in and powered up the CPU and printer boards. Activating new circuitry is always an eye wincing moment (for me anyway) and the hope is that smoke doesn't appear or things don't run erratically.

I was greeted by the "Error" display, so the CPU was working, (the Continuous Memory is ready but is switched off during testing), and the motor stayed off - good so far.

I wrote a small snippet of code so that I can test the motor from a command from the PC. I pushed the PC button and what do you know, it worked :-)

The motor control from the processor has 2 speeds, one for printing and one for homing the print head. Both speeds were working which is good because there is some board hardware, processor internal hardware and then the software controlling it, any one of which could have caused some fault finding.

From looking at a UTube video of the printer in operation, I cannot see a change in motor speed, but it is hard to determine. I do hear a sound change when the carriage is returning though.

Next is to test the print head home detect. This will be easier than the 97 printer I worked on, as you cannot damage the 19C printer mechanism if the motor does not stop at either end of its travel.

cheers

Tony