Set the free run switch up.
Connect the four leads of the Signature Analyzer in this fashion. GND to ground, START & STOP to A-15 (by the address bus LED's), CLOCK to READ ( also by the address bus LED's) {pictured in the powerpoint presentation}.
Set the Signature Analyzer’s START, STOP, and CLOCK push-buttons out (rising edge).
Verifying the Free Run Mode Take-up the probe (LED flashing on end) and put the metal point to the pins of IC’s 1 and 2. Compare the display of the Signature Analyzer to the code located in Appendix C-1 of the microprocessors’ manual. Any point may be cross-referenced in this manner. Try This Out Turn the microprocessor’s power switch off and then on again. The signatures of the data bus test points changed on account of new data now stored in the RAM. Hold the probe on the same data bus line and slide the corresponding input port switch (fiddle around to find the one). View the change of signature according to the switch position. Setting-up the SA Test Loop Set all of the data bus switches down to enact the Test Loop. Set the FR and SA switches down to put an end to the free run mode of the microprocessor. Connect the four leads of the Signature Analyzer to the pictured areas, add, the clock to the WRITE port. Set the Signature Analyzer’s START, STOP, and CLOCK push-buttons out (rising edge). Hit reset twice and now, move SA switch up then down. Verify the SA Test Mode Take-up the probe (LED flashing on end) and put the metal point to the pins of IC’s 1 and 2. Compare the display of the Signature Analyzer to the code located in Appendix C- 4 of the microprocessors’ manual. Any point may be cross-referenced in this manner. Finding a Simple Fault Remove W-10 from the center of the micro- processor’s board (one of the black plastic bits with a wire across it). Change the test set-up to match the information in table C-3 of the microprocessor’s manual.(all those switches we fiddled with to set-up the free-run and SA test loop). Give LED 4 the probe.(just below address display). A bad signature here points towards a problem from the IC doing the sending. Trace the signal back to output pin 12, IC 15. You will find a bad signature on this chip as well. De-solder and replace with like unit. Continued Hunting Probe the D4 input to the output port (IC15- pin13)and note the bad signature. Take the probe to the bus buffer output (IC15-13) for a good signature. It’s down to one PC trace. Probe the signal along the trace from IC15-13 heading to IC14-11, that’s the one. Put the jumper (W10) back…please click here for a power point version of the background information