Almost there! Fix one position and move two bulbs

 TRIAL INSERTION OF BULB MATRIX

With essentially every lamp holder in place, I tried to slide the PCB with lamps right into the honeycomb matrix. I still had to do a bit of wiggling and playing with holders that were skewed a bit, so this still doesn't meet my expectation for a rapid and effortless insertion, but it is much closer than any previous incarnation including the original IBM mechanism. 

Test fit of PCB with new holders behind panel

LAMP TEST VERIFICATION

Using the Lamp Test signal to turn on all the lamps, I had a chance to check that all the bulbs I installed were working properly. As you will see, two of the CE positions are dark because I was short two bulbs from having a fully populated board, but in addition the lamp for Index Register 2 is out. It doesn't light with a direct signal input either, causing me to suspect that it is an issue with the newly installed bulb in the holder assembly.

CE 4, CE 5, and IX2 are dark (for different reasons)

DOH MOMENT RELATED TO IAR AND MAR REGISTERS

If you look closely at the left side of the control panel, where the six major 16 bit registers are displayed, you will see that the leftmost (bit 0) lamps do not shine through for the top two rows. These are for the Instruction Address Register and the Memory Address Register. That is consistent with a system that can only address a maximum of 32K words, thus needs only bits 1 to 15 to contain all possible addresses. 

Since the machine does not contain signals to drive bit 0 of IAR or MAR, and the panel does not have an opening to allow the light to shine through on lamp test, there is no reason to populate those two positions. 

That gives me back two lamp assemblies, exactly what I need to fill in the missing two positions of the CE signal area of the panel. I don't need to wait for a new supply of 2114 bulbs to finish this up and install it in the IBM 1130.

WORK AHEAD

First, the two lamps from IAR bit 0 and MAR bit 0 will be moved to the CE signal area. Second, I need to check out the IX 2 circuit and lamp, repair it and retest to demonstrate all 162 lights active simultaneously.

Beyond that, I am exploring ideas for an alignment honeycomb that will slide over the lamp holder assemblies on the PCB, holding them upright at the correct position, so that the sandwich of PCB and the alignment part will slide easily into the display panel honeycomb matrix. I envision something produced with a laser cutter, material to be determined but likely some kind of plastic. 

That alignment part will be slid over the lamp assemblies while they are facing up and at the maintenance person, who can easily manipulate them into position to have the alignment part touching the PCB face. I have some measuring and noodling to do before I design and fab this out, but I suspect this will be the way to make this control panel upgrade a complete win.