VCF 1130 early testing shows substantial portions working well

LAMP TEST SHOWS QUITE A FEW BULBS ARE DEAD

The lamp test switch illuminates all the lights on the display panel, allowing quick identification of bulbs that need replacement. I didn't list everything on this first test, but did see that the T6 bulb is out as well as a block of four bits in the SBR register. There were other holes in the display but I have at least eight bulbs that can be used - the ones in the customer engineer row - then will figure out how to source additional ones. 

SINGLE STEP TESTING OF EXECUTION SHOWED THAT A LOT OF THE CPU WORKS

In single step mode, I can step the machine through each of the T clock cycles and watch it process instructions as the instruction cycle state changes. This looked very good - it grabbed data from memory, interpreted it as a one word instruction so it processed both the I1 state and then the E1 state to execute it. 

There can still be many failures in the machine, as this is far from an exhaustive test, but the primary clocks, states and run control are working correctly. I was very encouraged by this.

SPURIOUS LAMPS LIT ON CONSOLE PLATE

I saw the Parity Check lamp and the Keyboard Select lamps illuminated upon power up and all through the single step operation. I suspect these are errors related to driving the lamps and not the actual condition registered, which will really help narrow down the cause. 

I say this because if we had a parity error, the machine would have forced a stop condition and I could not have single stepped as I did. Further, the keyboard did not unlock, which it would have if the keyboard were really selected. 

CHECKED ALL PUSHBUTTONS AND CE SWITCHES FOR CONDUCTIVITY

I did check the operation of all the pushbuttons on the console plate, the rotary mode switch and the six CE toggle switches under the front cover, using a VOM to test resistance and operation. They worked correctly. 

NEXT UP - INVENTORY CHECK OF SLT CARDS AND GOOD SEATING

I listed all the SLT cards that should be in each card cage (SLT compartment) of the machine. I will go through each compartment, making sure all is in order. I will pull each card to check its type if I don't recognize it from other examples. For each card, I will verify that it is pushed into place on the SLT board (backplane). 

I suspect that I might have a few issues with cards that either came loose or where removed and not properly reinserted during the long rest this machine had in the warehouse. 

The most common issues I find when restoring 1130 systems are:

• Cards or connectors not inserted properly or in wrong slot
• Failed trace on backplane that requires wirewrap jumper
• Failed SLT card
• Oxidation causing switches to not make good connections

The rate of SLT card failures is quite low, in my experience. Trace failures occur one to a few times in each machine I have restored, so this more common. Oxidation and card insertion issues are the most common failures and fortunately the easiest by far to correct.