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Front Panel Testing DCC-116


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  Front Panel Testing DCC-116 by Bill Degnan - 12/31/2020 01:50
AJ holds a panel.
AJ holding the front panel from a DCC-116 mini computer. The DCC-116 is a clone of the Data General 800/1200. Click image for larger view.

DCC-116 front panel tester
AJ's front panel tester. Click image for larger view.

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On the front panel, apply ground to pins 1 and 17 (J4), 5 volts to pin 27, and 12 volts to pin 33. Once you do that the circuit is powered and no lamps should be on. If any lamps are "on" (lit) when you've set power to the board this way, you know that these lamps need an IC (or two) replaced.

DCC-116 front panel fault
The front panel undergoing a light fault test. Click image for larger view.

We found on my panel the following faults:
MB0 (address 0) pin 14 (did not come on)
Carry pin 49 (did not come on)
Address row lights 2 and 3 stuck on
Data light 8 stuck on.

NOTE to SELF: for DG backplane connectors all of the odds are on the bottom and all of the evens are on top. Refer to front panel schematic diagram

In addition to testing the front panel, AJ and I went through the controller cards and agreed on their correct position in the backplane. The duplicates and unnecessary cards were placed in the top backplane. We determined that there was no wire harness for.the top backplane.

NEXT: Replace the related ICs. Set up an Arduino script to test patterns.



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