Some Thoughts about Happiness

October 25th, 2016

When Thomas Jefferson wrote the first draft of the Declaration of Independence, he wrote of three inalienable rights. Among the three, was the “pursuit of happiness”. While some people think that the phrase, “pursuit of happiness” is about the acquiring of material wealth, as portrayed in the recent movie by the same name. In reality, that isn’t the case. Scholars know that Jefferson admired Epicurus, a Greek philosopher, who founded a system of philosophy. The following description of Epicurianism is from Wikipedia:

The philosophy originated by Epicurus propounded an ethic of individual pleasure as the sole or chief good in life. Hence, Epicurus advocated living in such a way as to derive the greatest amount of pleasure possible during one’s lifetime, yet doing so moderately in order to avoid the suffering incurred by overindulgence in such pleasure. The emphasis was placed on pleasures of the mind rather than on physical pleasures. Therefore, according to Epicurus, with whom a person eats is of greater importance than what is eaten.

So Jefferson was advocating a pursuit of happiness as an unalienable right, he was in essence advocating a pursuit of Epicureanism philosophy as a fundamental aspect of a free man’s life.

You might wonder why I am talking about Epicureanism. Why is it so important, that I would make an effort to share these ideas with you.

Well, I think that happiness is something that you should pursue, and it is absolutely worth pursuing. Happiness does not necessarily come automatically with other goals like attaining an education, advancement at work, raising a family, or striving for any other goal. Happiness should be a goal unto itself and you should pursue it, the same way that you might pursue your other goals. Those other goals may or may not bring you happiness, and, at best, attaining those other goals most likely will only bring you temporary happiness. Therefore, you should make happiness a goal unto itself.

Make sure that whatever you do in life, make sure that you set aside a little time each week to think about what gives you happiness and make finding a little happiness each week, one of your goals for that week. You may not succeed every week, but just thinking about it and working on a plan, should provide some hope for the next week. Furthermore, I believe you should encourage and help your partners, family and friends to find a little happiness each week.

This essay was written over the spring and summer of 2016 by Mike Willegal

SCELBI Oscilloscope Edge Connectors

October 15th, 2016
Edge Connectors Wired

Edge Connectors Wired

I have the edge connectors wired and ready to go into the chassis. It should be apparent why I wire these connectors before mounting them in the chassis.

The original unit used wire wrap, but I had these connectors on hand, and decided to solder the wires on, just like the cassette and tty interfaces.

If you follow the schematics, most of the connections are pretty apparent. However sync (BP) and the four strobe inputs (BB, BC, BD, BE) are not. Turns out that sync will go to pin 10 on P1. Out 0 on the main chassis needs to be connected to sync, just like needed to be done with the cassette interface. From studying the images I have, I think that the strobe inputs are spread out between pins 9 and 11 of both P1 and P2. Pin 11 is ground and pin 9 is the strobe output of each port. In this case, the ground inputs of the P1 and P2 connectors are not used as a system ground connection, but only as a low logic input connection. There is some chance that I will have the P1 and P2 outputs swapped compared to the original unit, but without original software or access to the original hardware, I can’t tell for sure which port was connected to which input latch.

I think when they built the chassis for the oscilloscope interface, they should have swapped the ports and the oscilloscope connectors. This would have reduced the length of a number of wire runs. Who knows, maybe they did make that change on later units, but unfortunately no others are known to exist.

SCELBI Analog Board Power Supply Installed

October 14th, 2016
Power Supply Installed

Power Supply Installed

This took a bit more time than expected, but at least the result is a little cleaner than I really hoped for.

I’ll wire the digital to analog board connections next. After that I’ll attach the power supply and external interface wiring to the edge connectors. I’ll mount the edge connectors in the chassis and connect the dangling power and interface wires to the appropriate connectors. I expect this to be pretty straight forward and go faster than all the previous steps to this project.

I’m not sure if I mentioned it before in this blog, but building the SCELBI Oscilloscope Interface is more complicated than building some basic computer systems.

Scope Chassis ready for wiring

October 11th, 2016
Inside Repro Oscope Chassis

Inside Repro Oscope Chassis

I bought several versions of terminal strips only to use a 4 postion version from Antique Electric Supply. I ended up cutting them down to make the three position set.

I’m going to wire up the power supply first, then wire in the edge connectors. Note that one side of the transformer shares a mounting screw with a terminal strip. Also, on the original unit, the edge connectors are mounted on a panel and secured to the mounting brackets. At the moment, I don’t have enough stock to make a full panel, so I’ve made a mini panel, and I’ll retrofit a full panel later on.

SCELBI O-scope Opamp Power Supply

October 10th, 2016

Here is a view of my version of the SCELBI O-scope Opamp Power Supply test setup. AC power is not connected in this photo, but would be connected to the transformer during the actual test.

Opamp Power Supply

Opamp Power Supply

I’m using a Triad VPL28-180 transformer and 1N4002 diodes. I found the diodes in my spare parts stash. The first smoothing capacitor is rated at 100uf/50 Volts. The +18 and -18 supplies have 470uF/25 volt smoothing capacitors. The latter are probably overkill, but it’s what I could find in my spare parts stash. The resistors are rated at 120 ohm, 1/4 watts. The zener diodes are the BZX79C18 that I mentioned in a previous post.

After hooking up to the analog board, the voltages are within a volt of +/- 18, with no measurable ripple. Transformer output is a little higher than with the original transformer that I tested with, but not enough to be of concern. Zener shunt current is OK, so I’ll just move this set up into the enclosure, without changing any components.

SCELBI O-scope Chassis Progress

October 8th, 2016

Well there is a reason why I changed majors from mechanical engineering to computer science.

SCELBI Oscope Front Panel

SCELBI Oscope Front Panel

A few imperfections in execution, but it will look fine when the connectors and switches and such are added. This is a Bud AC413 chassis, the original chassis was constructed a bit differently, and 1/2 inch higher. I didn’t notice the Z and G when making out the rub-on artwork, but fortunately I included some extra text including an extra “GND”. The N turned sideways makes a decent Z.

I have a few more coats of clear lacquer to spray before moving onto the next stage.

For Comparison, the following is an image of an original SCELBI O-scope Chassis taken by Jack Rubin. It has been slightly photo-shopped to fix the perspective.

SCELBI Oscope Original Front Panel

SCELBI Oscope Original Front Panel

SCELBI Keyboard Interface All Hooked Up and Running

October 1st, 2016
SCELBI Keyboard Interface All Hooked Up and Running

SCELBI Keyboard Interface All Hooked Up and Running

For now, I’m using one of my PS/2 adapters (on top of the enclosure) to connect to a PS/2 keyboard. I was going to cobble together a cable for my reproduction Datanetics keyboard, but it requires -12 volts, which would have to be generated separately just for this keyboard.

Now I can focus on the Oscilloscope Interface.

Wiring the Keyboard Interface Enclosure

September 30th, 2016
Wiring the Keyboard Enclosure

Wiring the Keyboard Enclosure

At this point, I decided to call it a day and said to myself, my next project isn’t going to involve so much point to point wiring. Counting both chassis, the peripherals and cabling, I must have soldered about 500 point to point wires during the course of the SCELBI project.

By the way, I think the best process for constructing one of these enclosures is as follows.

  • cut and drill the holes
  • add the rub on lettering
  • clear coat the lettering with lacquer
  • add the connectors
  • wire it
  • There are 12 wires left to connect on this chassis.

    For the oscilloscope interface checkout, I think I’m just going to build it up in the chassis, rather than test it and then make the chassis.

    SCELBI Keyboard Peripheral Enclosure nearly done

    September 28th, 2016
    Peripheral Enclosures

    Peripheral Enclosures

    Internal wiring is left to be done, but the mechanical part is ready for wiring. Note the front panel layout is reversed from the cassette interface. It turns out that I have seen the cassette interface made both ways. Stuff like this happens when your products are hand made.

    SCELBI – Oscope Digital Board

    September 20th, 2016
    OSCOPE DIGITAL PCB - front - with rework

    OSCOPE DIGITAL PCB – front – with rework

    SCELBI OSCOPE DIGITAL PCB - back - with rework

    OSCOPE DIGITAL PCB – back – with rework

    Notice that I have also recreated the rework. Note that the proper way to cut a trace on a PCB, is to use a sharp hobby knife to make two parallel cuts in the trace an 1/16″ or so apart. Then you remove the small piece of copper between the cuts.

    The Analog board has also been built. What’s left is wiring up the board edge connectors to power and amphenol connectors.