PDP-11/10 repair started

Johnny Billquist bqt at update.uu.se
Sun Oct 4 19:27:24 CDT 2015

On 2015-10-04 20:09, Henk Gooijen wrote:
> Some corrections to my post regarding the console LED behavior.
> Voltage levels on the CPU backplane are still good whne the 2 CPU boards
> are installed in the backplane, but the processor is not responsive to
> the switches on the console panel.
> The RUN LED is on, ADDRESS/DATA are all off. When the HALT/ENABLE switch
> is in the HALT position and START is toggled ("reset"), the RUN goes off
> and the ADDRESS/DATA LEDs all go on.
> LOAD ADDR, EXAM and CONT have no response.
> When I set HALT/ENABLE switch to ENABLE and toggle START, the RUN LED
> goes on and DATA/ADDRESS LEDs go off, except LED "0".

You mentioned NPR problems before, but I have never seen a broken NPR 
signal cause any problems at power on. Broken NPR normally cause DMA to 
not work.

However, what you describe sounds exactly how I've seen a lot of 
machines behave when the terminator is missing. Check for bus 
continuity, and termination.


Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol

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