Wednesday, November 9, 2016

Preparing to study the circuit failure in the Diablo drive

Spent part of the day at Computer History Museum working on an odd problem with card reader errors that occur only when executing op code 3 - a combined instruction that writes a line on the 1403 printer and then reads a card. 


I am going to stick the Diablo data separator circuitry onto the logic analyzer to understand more deeply what is occurring in those times where the circuits fail to properly handle timeshifted transitions and report a clock pulse as a data bit, for example.

Points to capture and feed to the logic analyzer

To do this, I can relay on three test points but still need to attach to three pins on ICs deep on the board. The board sits in a group of PCBs such that the surface of this board is fractions of an inch away from the back of the adjacent board.

There is no room for traditional grabbers without using a board extender - which I don't have. I tacked solder wires on the outsides of the selected chip pins so that the wires extended out of the congested area.

The lines were hooked up to the logic analyzer and ready to begin testing tomorrow morning. 

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