Powered tests of the functionality of the board - everything working very well

 MAKING CONNECTIONS TO THE TERMINAL BLOCKS

The board requires a common ground between the SLT logic level DC (0 or 3V) and the 7.25VAC lighting power. The other leg of the AC supply is hooked to the top terminal block. Finally, the Lamp Test block on the bottom is hooked to a switch that ties it to ground in the normally closed position and flips the Lamp Test line to 3V DC when moved to the normally open position. 

NO LAMPS INSTALLED, VERIFY NO CURRENT FLOW AND NO AC ON SIGNAL PINS

With the AC turned on but no lamps or inputs connected, the board should not consume any appreciable current on the AC level - and it did not as it was less than one ma. I also checked that AC was not presented on any of the 164 logic input pins. 

SINGLE LAMP TEST OF LOGIC 0 INPUT, LOGIC 1 INPUT AND LAMP TEST

I inserted one bulb to verify operation of one of the 164 lamp circuits. With no connection to the input pin, the lamp did not light. With a simulated logic level applied the bulb lit up. This was done with +3V applied through a diode and a 6.2K resistor, matching the output driver inside the 1130 that provides the signals to the control panel. 

I flipped the lamp test switch, putting +3V on that control line, and my bulb lit with either logic 1 or logic 0 applied to the input pin. This represents a full test of the operation of one lamp position. I know that the basic circuit is working properly

MULTIPLE LAMP TEST VERIFYING INDIVIDUAL SELECTION AND MASS LAMP TEST

I installed five bulbs onto the board and switched on again. Nothing should light with Lamp Test off and no logic 1 applied to the input pins. None did. I hooked up three logic 1 levels to three of the circuits and left the other two at logic 0. Those three bulbs lit and the others did not. Finally, switching on Lamp Test caused all five bulbs to illuminate. Again, all good. 

Three signal lines switched to high, Lamp Test switch in off position

FULL UP LAMP TEST WITH ALL LAMPS INSTALLED

I built a quick and dirty tester for lamps to make sure that the wire leads were not shorting before I plugged them into the board. It was a bit of header strip in a breadboard with my ohmmeter in line to check the cold resistance of the bulb. I could distinguish between dead (open) lamp, shorted wires and a workable lamp using this setup. 

I inserted the board with all the lamps into the honeycomb matrix of the front panel. This would let me access the signal pins on the rear, protect the lamps inside and let me watch the illuminated positions from the front. With all lamps installed, I repeated my check to verify that none of the 164 logic input lines were seeing AC. This was key to protect the 1130 circuitry from damage when I install this upgrade in its control panel. 

I powered up and verified that no lamps were lit in the absence of an SLT logic 1 level on its input. I tested all the circuits to verify that they operated correctly with my logic 1 inputs on their pins. Finally it was time to flip the Lamp Test switch and verify that all the lamps lit up properly.

The current measured during steady state of the lamp test was hard to measure since my ammeter didn't support high enough current and none of my AC supplies have current measuring capabilities. 

Even worse, the puny AC power supply couldn't put out the current demanded by the lamps when all were on, thus the voltage dropped to about 5VAC and the lamps were all quite dim. I checked for signs of hot spots and was satisfied with the thermal performance of triacs and the board since everything was cool as can be, loafing alone under the dim version of the Lamp Test. 

Lamp Test switched to on position, power supply struggling to keep up

CHASING DOWN AND FIXING PROBLEMS DETECTED DURING THE TESTING

Accumulator Register Bit 6 did not light with the Lamp Test activated. The lamp lit properly for a logic 1 applied to its input pin, but did not react to Lamp Test. I traced this down to lack of connectivity from the 6.8K resistor to the gate of the triac. After a quick repair, I reinstalled a lamp to verify that ACC 6 does light under Lamp Test. 

Operation Bit 2 did not light with Lamp Test nor with direct logic 1 to the signal pin. This was a poor solder joint on the gate pad of the triac. Resoldered and tested.

Tag Bit 7 did not light with Lamp Test but did work with logic 1 on the signal pin. The 6.8K resistor was not connected properly. Resoldered and tested.

REC signal of the Synchronous Communications Adapter did not light with Lamp Test nor with logic 1, but did when I wiggled the socket. Poor solder on one of the pins of the socket. Resoldered and successfully tested.

Odd Status lamp was always illuminated even though logic 0 on the input pin and Lamp Test not activated. Found a bridge on the triac between the output 'anode' and the gate pad. Removed and replaced triac, then tested successfully. 

My original designs did not attempt to light the 8 Customer Engineer (CE) bulbs nor light the signals from the Synchronous Communications Adapter (SCA) since that feature is not installed on my machine. However, this new board is universal and includes those positions. However, when I built my lights - wire lead light bulbs soldered onto two position header strips - I didn't build the extra 16 needed to fully populate my board. 

NEXT STEPS

I have to build another 16 bulbs and install them into their positions for the CE and SCA displays. 

I want to work out a good fastening or clamping method to hold my board onto the honeycomb. 

It would be reassuring to find a high capacity AC power supply with current measuring capability and hook that to my board so that I can verify how it operates with the 148 currently installed bulbs. That should be close enough to the fully populated load of 164 to feel comfortable installing this into the IBM 1130.

The console should be put back together, my board wired into the 1130 with all the signal lines attached to the signal pins on the back. That will allow for a full power on test with the actual computer, the final certification of this design to replace the kludgy IBM incandescent lamp mechanism that came with the system.