PDP-11/10 repair started
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
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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