TYPE 340 round display question

[R Clark]

Looking at pictures on the web, I see  hole/knob/switch or something in the lower left corner of the display panel.  Wondering what that was if anything. I freeCad'ed a simple box and added a small hole in that corner.  I can drill out to size as needed (or re-cut) after I laser cut the pieces. You see, I bought a 5" hdmi round touch screen from Waveshare to hopefully sort-of recreate the 340 display for fun.  Since the PiDP-10 is on a shelf and the RPI-5 hdmi connectors are being unused...  Anyway, see where project goes...  This hobby is addicting...

[Tim Radde]

I can't find a decent picture on the web that shows this. Can you provide one?

[Stephen Jones]

Courtesy of SDF Vintage Systems.

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[david avery]

pretty sure that is the display brightness control knob

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[R Clark]

Thanks for the hi-res picture!!!  I couldn't find a good one on the web either.  

So a smooth silver control knob with a black center to control the brightness.  

[Stephen Jones]

On both Type 340s here the potentiometer on the bottom left adjusts the gain control for the light pen.

Brightness and other adjustments are done through the PM calibration procedure.

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[Stephen Jones]

Your welcome, also this video of the Type 340 on our PDP-7 might be useful as well:

https://toobnix.org/w/8AiLyAECTVyKehG5KT1Mx7

On Sun, Apr 6, 2025 at 7:32 AM R Clark <rbclar...@gmail.com> wrote:

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[pbi...@gmail.com]

Pretty interesting multi-media presentation :-}.  Thank you for sharing it.

 

1. What phosphor does the Type 340 use?
2. What is the source of the audio?
3. Is the source code available for study?

 

It would be interesting to reproduce these outputs in other environments!

 

From: pid...@googlegroups.com <pid...@googlegroups.com> On Behalf Of Stephen Jones
Sent: Sunday, April 6, 2025 6:26 PM
To: R Clark <rbclar...@gmail.com>
Cc: PiDP-10 <pid...@googlegroups.com>
Subject: Re: [pidp-10] Re: TYPE 340 round display question

 

Your welcome, also this video of the Type 340 on our PDP-7 might be useful as well:

 

https://toobnix.org/w/8AiLyAECTVyKehG5KT1Mx7

 

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[Lars Brinkhoff]

1. What phosphor does the Type 340 use?

P7 

[Stephen Jones]

P7 phosphors. The audio was captured by holding a yaesu uv8dr near various places around the controller backplane tuned out of the AM broadcast band. Both listings and more can be published on SDF’s git server soon! 

Both our Type 340s operate but we need to fabricate a controller to used the pictured one on our PDP-6.  More details on its analogue rebuild soon.

[Lars Brinkhoff]

SMJ wrote:

Both our Type 340s operate but we need to fabricate a controller to used the pictured one on our PDP-6.  More details on its analogue rebuild soon.

Wow, you'll be able to demo SHRDLU in style!

[Bradford Miller]

What is the panel that was cut off on the right of the picture?

> On Apr 5, 2025, at 8:32 PM, Stephen Jones <sdfp...@gmail.com> wrote:
>
> Courtesy of SDF Vintage Systems.
>

> <IMG_9400.jpeg>
>

[Lars Brinkhoff]

Bradford wrote:

What is the panel that was cut off on the right of the picture?

A PDP-8 "straight eight".

[steve...@gmail.com]

Photos of the "Classic 8" I used to own:

[R Clark]

Getting closer!  Nothing 'fancy here' . Note this is a 'phone' picture and the color is 'off' (more bluish).  Sitting on my desk it looks almost the right green color.  Go figure.   Thought I'd show my progress anyway.  I wrote a program to simulate the scope (pixels fade if not refreshed) and display a strange attractor on it.  Not hooked up 'yet' to the PDP-10.  Just playing around learning how to use the round display.  Right now I have two displays  hooked up on RPI. The round being the second display.  Easier that way.  As I said in another thread I really need to redo the proportions for the actual display viewing area (not the full width of the display). Ie. the front panel is bigger than it should be.  Live and learn.  Note the display is a touch screen, so could add the 'pen' capability....  We'll see.

[Stephen Jones]

This is very cool and you even have the screw holes for the shroud as well as the gain pot for the light pen.

The light pen has a mechanical gate, but maybe you could make a button for that and allow your finger to

take advantage of the touch screen.

Next, can you emulate this effect? :)

https://mastodon.sdf.org/@icm/114676332873035528

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[R Clark]

Here it is with the knob attached. Still have to automate the pot to modify the intensity of the screen, but now the hardware is done.  Up to the software now :) .

[R Clark]

Display Update: The Waveshare 5" round display failed.  Bought March of 2025, Died January 2026.  I had it on 24x7.  Not sure if I am going to replace it if I have buy one every year...  Just an FYI.  So now it is just a knick-knack on the shelf :) .

[R Clark]

Oh, I did automate the pot, so I could change the intensity of the display by turning the knob. It 'was' working good.  

It was just sitting on the shelf when I noticed the screen turned white-ish and about 1/8 of the top was black... You could just make out the drawing on it....  Reboot and resetting cables did not help the situation.

[James Cloos]

>>>>> "RC" == R Clark <rbclar...@gmail.com> writes:

RC> It was just sitting on the shelf when I noticed the screen turned white-ish
RC> and about 1/8 of the top was black... You could just make out the drawing
RC> on it.... Reboot and resetting cables did not help the situation.

i had a (rectangluar) oled do that, after running just xclock(1) on it
for a year or two. (ntp-correct time of course.)

i gave it another try after a couple of weeks (or months??) on the
shelf and it worked again.

yours might recover too. with luck....

-JimC
--
James Cloos <cl...@jhcloos.com>
OpenPGP: https://jhcloos.com/0x997A9F17ED7DAEA6.asc

[R Clark]

No luck.  So, bit the bullet, and bought another Waveshare 5" display.  Back in business as new one works great.  This time I won't leave it on 24x7 ... maybe extend it's life if only use for demo purposes.  Treat it like a 'museum' piece ;) .

[sunnyboy010101]

Thanks so much for describing the problem. Based on what you discovered, I wrote a simple script and made a desktop shortcut to it that allows me to turn the HDMI on or off. Most of the time now I keep it off to preserve the small HDMI screen (mine is Elecrow rather than Waveshare due to cost in Canada).

The only issue I've had running the script is that it removed the Type 30 window when run. As a result I stop the simulation first, change HDMI status (either off or on) then restart the simulation. Not ideal but works just fine for me.

Again, thanks for writing about the HDMI display issue.

[R Clark]

Your welcome.  I attached a snapshot of the problem display. It 'should' be almost black background,  See above posts for examples...