New Apollo items loaned to me including a late model EL panel

The collector who had loaned the three Apollo items to me for my display project brought over three more yesterday! I have a later model Electroluminescent Display Panel which should glow with the correct colors that were visible to the astronauts. He loaned me a second relay module which I will test out. The third item is some kind of display that marketed at auction as coming from an Apollo Command Module but we are not certain.

MYSTERY DISPLAY EXAMINATION, REASONS TO DOUBT IT WAS IN THE SPACECRAFT

The new display has identifications that tie it to Marshall Space Flight Center (Huntsville Alabama), the designer and system integrator of the Saturn V and IB vehicles. The only information I could find on the contract number is that it was finalized in June of 1967. That is relatively late in the design cycle for Apollo. 

Secondly, looking closely at the frosted glass front I can't see any signs of traces to suggest this is electroluminescent, as stated in the auction and as used throughout the spacecraft due to the very low power consumption of that technology. 

Third, its connectors on the rear are a pair of circular sets of solder pins, much like only vacuum tube sockets. This kind of connector and reliance on solder would not have been used in the spacecraft.

Fourth, its body size is much taller and wider than the visible screen area. There is no location in any of the Apollo spacecraft, CM or LM, where we find a similarly shaped indicator. More importantly, no spot has reserved space free of other indicators or controls to match the tall and wide shape of this object. 

Our conclusion is that this is an indicator of some sort procured to support the Apollo program, but likely was used in some ground support equipment. I looked at images of every console in the KSC launch control room as well as all the mission control consoles at JSC, but none had that indicator attached. 

I is probably one of those displays that shows numbers by mechanically moving masks so that the incandescent bulb inside shines on the frosted screen with the pattern of the desired digit(s). Big and bulky enough to house the lamp, solenoids and moving masks. 

Connectors on mystery indicator module

SWITCHING TO THE NEWER EL PANEL MODULE

I switched over to the newer EL panel module, which was boxed and appeared to be an unused spare part thus new-old-stock. When I activated it, the brightness was dramatically better. More importantly to me, it had the proper wavelength. The early version I previously had used was shifted to the blue-green while this one is a nice central green that would have been the color seen by all the astronauts and technicians. 

The COMP ACTY segment works as well, a nice bright rectangle that was illuminated when the Apollo Guidance Computer was running any code other than its idle task. Thus the flickering and percentage of time it was illuminated gave an indication of CPU busy. 

I wired up another driver circuit and the relay in the Relay Module that was used to drive this indicator. That relay is NOT a latching type. It is only energized when the input signal is on. 

New-Old-Spare display panel in operation

GOING FOR BIGGER THINGS, ADDING THE SECOND RELAY MODULE

Next up I am going to wire up the second Relay Module to control the five digits in the R1 row on the display. Those are to the right of the sign I am already driving. This will require five new driver circuits, 93 additional pins, a new relay module plate for the connector, and lots of additional wirewrap connections. 

Normally, to drive the five digits would require five selection line drivers, five column latch drivers, and five column unlatch drivers. However, I realized that I could double the connections from my existing latch and unlatch drivers that are wired to Relay Module 1. As long as I only select the row in one of the modules at a time, this is okay as current will only flow through one relay coil at a time. Thus, I have discrete row select drivers but share the latch/unlatch outputs.