RK11-C indicator panel inlays?

David Bridgham dab at froghouse.org
Mon Dec 6 08:42:00 CST 2021

On 12/5/21 3:24 PM, Ethan Dicks via cctalk wrote:

> This would be really cool as a debugging tool
> more than just as amazing lights.

A great lead-in to my story.  I was working away on the RK11
implementation in the QSIC and when I felt like taking a break but still
wanted to get something done, I'd work on the indicator panel.  Of
course, the indicator panel ended working before the RK11.  Just having
144 lights that I could assign to any purpose was useful but then came
the day when the RK11 was mostly working.  I loaded up an RK11 exerciser
program that Noel wrote and just sat back to bask in the glow of the
blinking lights.  It was a good feeling.

Then I noticed something that wasn't right.  Even though the exerciser
was working, I saw a pattern in the lights that showed up a bug in my
implementation.  I'd really only implemented the indicator panel because
I thought it was fun but it lead me to a bug to fix right off.

Here's a short video clip of the indicator panel in operation and
showing that bug.  I'll leave this for a day or two (or until I remember
again or someone asks) and then say what it is I saw.  I think anyone
with a reasonable familiarity with the QBUS will be able to pick it out
though I'll say that "Latched Address" is the address "half" of the
data/Address Lines, that is the value of those signals when SYNC is


> P.S. - not to derail things, but definitely loop me in on the (future)
> thread for making reproductions.  I have access to some tools that
> might make parts of it easier.

The inlays are mostly not done with any tools I have.  I do the graphics
with Inkscape.  Rod made up the blanks with silk screening.  Then I have
the white printing done at a printshop I found who has a large, flatbed
printer that can print white ink.  I do have some ideas about how I
might try to make up blanks with a laser etcher I have access to but at
the moment we have an ample supply.

Also, I've experimented with making my own bezels out of PVC board from
Home Depot using a CNC router.  In the pictures below, the yellowed
bezels are old DEC bezels while the white ones are ones I made.  I
figured that if we ever get the QSIC shipping and people want indicator
panels (I hope they'll want indicator panels), I'd rather not depend on
them ripping apart old DEC bezels to make this work.

Anyway, I'd be most happy to have another person with more tools to help
build bits and pieces of this stuff.  I've noticed that as I gained
access to different tools, I came up with different ideas about how to
make things.  I didn't think the laser etcher was all that useful until
I started using it.  Now I want to use it for everything.  Turns out it
can't quite handle 3/8" Delrin; it just melts it and makes a mess. 
Speaking of help, if anyone wants to review the QSIC design, I'd welcome
that.  This is by far the most complex circuit board I've ever designed.

Back to indicator panels, here's a picture showing a bit of the
evolution of my indicator panels.  The video above shows it really
early, when I just taped a paper inlay to the circuit boards.  Then the
bottom panel in this picture is taping that paper inlay to an MDF light
shield.  The top panel is using one of Rod's blanks with paper labels
taped to it.  And then the third panel down is a printed inlay like
we're talking about now for the RK11-C.  The second indicator panel is a
TC08 inlay that I borrowed from Noel to use as a model as I worked on
the graphics for our own.


Here's a close-up of the TC08 and our printed inlay.  I'm rather pleased
with how it looks, I have to admit.  The only real thing I'd like to
change is the gloss.  Somehow, DEC's inlay is as flat as flat can be. 
There is no glare to it whatsoever while ours are quite glossy.  I've
looked at frosted acrylic and it's a little better though really it just
diffuses the glare, it doesn't eliminate it.  I've also tried some
spray-on frosting which helps a little but it also has a tendency for
its solvents to melt the printing that's already there so that's a bit



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