Wednesday, May 1, 2019

Working on installation of the IBM 1130 light panel using LEDs to simulate incandescent bulbs

Wiring and assembly of power supply

I have the two filter capacitors mounted on the swing down rear door, along with the bridge rectifier module. Next I assembled the two buck converter boards onto the laser cut adapter plates I made. These were also mounted on the door.

I did discover that the filter capacitors were too tall to fit in the orientation I expected, but if I swing them 90 degrees they could be oriented in the long (width) direction of the enclosure and fit properly. I did some test fitting of the adapter plates and components until I was satisfied with their fit.

Components of power supply in place across rear door of panel enclosure
With all of these installed in place I could finalize the lengths of the wiring and begin wiring them together. These are soldered in some places such as the PCBs, attached with lugs onto screw terminals in others, and inserted into screw tightened terminal blocks for the remaining connections.

The use of lugs permits removal of the PCB along with the harness and supports replacement of any modules that may fail in the future. I made use of color coded wiring - black for ground, yellow for 7.5VAC, blue for rectified unregulated voltage, green for 3.3VDC and red for 5VDC. A white wire connects the Lamp Test voltage from the computer to the signal input pin on my PCB.

After completing most of the wiring harness, when I was ready to solder the last few connections, my Weller soldering station expired. Something went wrong in the tip (PES51) and the station is dead in the water. Replacement coming later this week, thus will continue wiring power supply at that time.

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