Odd Symptom PDP 8e Running Programs

[Bob Smith]

Bill,
I am assuming you have done all the usual after a physical move of the system -
reseated all the boards and whatever we called those green blocks on
top of the board pairs, and cables - both ends.
If not, that might be the hint the system is giving you.

That is about all I can think of something more than 40 years since I
trouble shot an /e/
bob

On Sun, Dec 15, 2019 at 12:10 PM Bill Degnan via cctech
<cctech at classiccmp.org> wrote:
>
> Hi - I am looking for some help.
>
> I have had a PDP 8e with RK05 drives that has run pretty reliably for many
> years, but after moving it a strange symptom has come up, preventing it
> from operating correctly.  I am hoping someone can advise.
>
> Here is an example
>
> 1.  Power up drives and PDP 8e
> 2.  Load OS/8
> 3.  Load ADVENT
> 4. Program loads, asks if I want instructions.  I can enter Y or N and the
> system responds.  The familiar scrolling light pattern appears on the front
> panel to indicate awaiting input
> 5.  As soon as I attempt an action such as "S" (with no quotes) the front
> panel freezes and I have to CTRL+C to exit ADVENT, dumping me to the dot
> prompt.
>
> Similar issue when running the MUSIC.SV program. I can load the program and
> get up to the point of entering a song, but when I enter a song name the
> system freezes on the first note.
>
> BASIC works fine however.  Which tells me that I have a CPU problem, not a
> RAM problem but this is just my hunch.
>
> Any ideas how to diagnose this?  Running MAINDEC programs is always
> frustrating. I am attempting to load the main DECX8 SYSTEM EXERCISER to see
> if there are any clues from this as to the cause of the freezing system.
> .
> https://www.pdp8online.com/os/os8/os8_cmd.shtml#DECX8
>
> Thanks
>
> Bill