On 2 Mar, 2008, at 14:41, cctalk-request at classiccmp.org wrote: I find that about half of all CPU faults on my 1301 can be found from the front panel, but then it is a remarkable front panel. I can slow the clock rate down to three pulses per second and watch the individual steps in each instruction, watch data shifting through the registers, watch the carry bits in the mill, watch the instructions shifting through the registers etc. I can even run it at one pulse per button press and change the data in the registers and create parity errors and write them to core and read them back and watch the parity checker do its stuff. Not so useful with peripherals though, I find a storage scope is invaluable for them, the more traces the better, so I suppose a logic analyser would be useful, but does one exists for MINUS 6.3 volt logic? I always presumed they were only invented after silicon replaced germanium and so only work with positive logic voltages. Probably out of my price range anyway for home use.