COMPLETED THE CONNECTION OF BROKEN OFF PIN TO EXPOSED SCR NUB
I worked out a way to hold the broken off pin in forceps, with some tape insulation to keep it from sucking away the heat as I solder. I was able to zip tie the forceps along the PCBs of the display panel so that it held the pin directly against the exposed metal nub of the SCR.
I had hacked away some plastic since the pin broke off flush with the surface - this gave me enough metal that I could solder to it. I practiced this with another SCR that was loose, before attempting the repair in situ on the PCB.
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| Broken pin was in the center of the rear face |
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| Successful connection on the test SCR |
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| Holding broken pin in forceps |
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| Aligned in position ready to solder |
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| Successful repair |
SBR FULLY OPERATIONAL NOW, CAN HAVE CONFIDENCE DEBUGGING PARITY ERRORS
When the 1130 takes parity errors in the upper 4K, it displays some bits in the SBR as well as the two parity bits P1 and P2. If I have all 16 lighting up in the SBR, I can evaluate whether there is or is not really a parity error.
Each side of the SBR, the first or second eight bits, has its own parity bit. The scheme is that the eight bits plus the associated parity bits must have an odd number of 1 bits. If I see that the bits are indeed odd for both halves, then the failure is a false parity detection driven by some more subtle error. If I do see that the parity is even in one side or the other, I can perform lots of reads and writes to detect a pattern as to which bit(s) tend to have the issue.
BUILDING MORE LED BULBS
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| My nemesis, the IBM 1130 display panel interior |
Each time I can force myself to sit down at the soldering station, I convert more holders to LED bulbs using the labor intensive process I worked out. I don't even have enough LEDs and resistors for the entire panel worth of bulbs, but the needed parts are on the way and should arrive in a couple of days.
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| Start with an LED |
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| Tie a resistor on one lead |
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| Solder the resistor to the LED lead |
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| Trim off the LED and resistor unwanted leads |
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| Line up some 26ga bare wire |
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| Solder the wire to the other LED lead |
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| Cut off the excess LED lead |
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| More 26ga wire to attach to other end of resistor |
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| Soldered wire onto resistor |
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| Trim off resistor lead |
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| Insert into nylon bulb holder |
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| Lock wires into holder |
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| Trim off excess wire |
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