Almost done building bulb assemblies for 1130 light panel, beginning on 1402 relay tester

IBM 1130 LIGHT PANEL UPGRADE

I continued soldering together lamp assemblies, completing one of the two small PCBs by midday and starting on the final small PCB. I have 24 more lamps to build and I will be done. Completed 132 assemblies of the the 156 used in the light panel.

The supply of incandescent bulbs I bought worked out well. The bags were sold as containing 100 bulbs but there were quite a few more in the first bag I used. The quality control inspection was as casual as the counting.

A couple of bulbs had the two wires exiting the glass envelope too close to each other, making the risk of accidental short circuit too high. One bulb was a different shape and barely glowed. Another bulb did not keep its vacuum seal and smoked inside when illuminated. Two bulbs didn't light at all.

Still, I had more than 100 good usable bulbs in the bag, a great deal for the price. The only downside to the deal was waiting weeks for it to arrive from China. Glad I have a test circuit to check each finished bulb assembly, which is how I found the dead bulbs, although after I had soldered them onto the headers.

1402 RELAY TESTER CONSTRUCTION

I thought I had everything in hand but got a call from Stan. He remembered that after he created the original wiring diagram, Ron Crane had recommended a modification that was not copied to the diagram. It involved another resistor and additional wiring. Stan didn't remember the details.

I went to CHM, opened the working tester, and took detailed photos. I also learned the value of the additional resistor, which is a 0.1 ohm 2W unit. Anchor Electronics was just about to close at 3:56PM when I rushed in and picked up that resistor.

Careful measurement of the case and the relay sockets gave me the information I needed to plan out the exact spot for holes and rectangular slots on the cover. I will be soldering up the wires and resistors to the relay sockets on my workbench, then inserting the wires/parts through the slot when I mount the sockets.

The important question is how I make good contact to the relay socket. Soldering will be hard as the metal fittings are a close fit to the plastic body, which will melt from heat very easily. I could wedge wires into the connectors, although that means some parasitic resistance is introduced. More thought is needed for the build process.