Do you personally use a plastic solderless breadboard?

I saw a neat variant of that. The circuit board was correct but the designer hadn't realised that the documentation showed the IC from the "wrong side", i.e. the way the chip packaging people viewed it. First samples of ICs, and all that.

Magic smoke left the chips.

Solution: through holes, so mount them on the other side of the board - problem solved.

Always true!

A plain old "sun lamp" bulb also worked well. Dunno if those are still readily available these days, since you'd think that by now most everybody would be clued into the skin cancer bit. On the other hand you can still buy a Big Mac on most any street corner, so who knows?

Best regards,

Bob Masta DAQARTA v7.60 Data AcQuisition And Real-Time Analysis

Oddly, if you say "90 degree bend" to someone doing a "tape up" (using real tape), it assumes that they are actually producing a radiused line with the tape, instead of a sharp 90 degree corner. Those were called "cut corners" to allow for the distinction. Of course with computah layout software a 90 degree bend is whatever the software uses for such things, which could be anything from a sharp corner to a pre-defined radiused curve.

I might be guilt of accepting conventional wisdom without verification. I've looked at various microstrip designs with a TDR in the past, but have always concentrated on material transistions (connectors, component leads, transfomers, couplers, etc) and not glitches along transmission lines. When I had to make a right angle turn with a microstrip, I simply chamfered the corner in the conventional manner and never tested if it made any difference. Were I do a microstrip tomorrow, it would probably use chamfered corners on the assumption that it's safer to follow conventional wisdom.

However, it's interesting that you found no reflections from a 90 degree bend (or corner)? I've never even bothered to look, mostly because I've never had a TDR with enough sensitivity or bandwidth. I did some Googling for examples and found this: which shows a TDR display, and follows with layout suggestions including chamfered corners on traces. The text of the article indicates that there are corner reflections, but I don't see them on the scope trace. That's what I would expect, as most of the reflections are coming from material transistions (connectors, leads, components, etc).

When I had to go through the board, I sometimes added extra vias to simulate the width of the strip line. I never tested if it made any difference.

I had things much easier in the 1970's. Components and products were much larger. Higher power consumption was tolerated. Standards and environmental were more liberal or didn't exist. Product life cycles were longer. Computers were still a design aid and not a necessity. Designs and protocols just weren't that sensitive to reflections for it to be an issue worth investigating.

Good point and another reason I wouldn't use my PCB for a job interview. See: Note that they have large "CIRCUIT" and "COMP" labels, with the correct orientation. However, they are outside the board outline, which means they might disappear from the negative, and certainly will disappear from the step-and-repeat negative used to produce the actual PCB's. These labels should have been on the actual PCB. However, that was easier said than done because of lack of room. I try to put them underneath a large size component, where hopefully, there are no traces. That's usually not the case. When I put the labels in the trace area, the size of the labels are usually too small for the PCB fab shop to easily see. Despite them allegedly looking for such labels, they often missed them. When I stupidly used "CIR" and "COMP", someone managed to misread them, and reversed them anyway. For this board, I ran out of board space, so I gave up and put the labels outside of the board area, and hoped for the best.

Notice that the shorting bar needed to electroplate the gold contact fingers is missing. My fault, but easily fixed by the PCB fab shop (for a price).

I added some more photos:

Notice the silk screen at: Those are NOT computer generated letters and patterns. They were done with an India ink pen and a collection of templates. Sometimes, I would use stick type and stick on component outlines, but mostly pen and ink. Examples of some of the templates used: Notice the 1:1 templates. Those were used to make a cardboard mockup of the PCB to make sure that the big parts would fit. When using pen and ink to make the silk screen, it was necessary to elevate the template, to prevent ink from running under the template. I had various schemes for doing that, but mostly it was several layers of masking tape on the bottom of the templates. One had to be very careful not to let the masking tape touch recent ink lines or they would smear.

My examples of stick type or rub on letters is long gone. There were also machines that would produce such rub on letters in strips.

For the silk screen, I used Koh-I-Noor pens. The pen tips are similar to plotter pens. Fast dry ink was nice, but clogs to quickly. Slow dry meant that one had to be very careful not to touch the lines before they were completely dry. The pen also had to be held perfectly vertical, or it would dump a blob of ink on the mylar.

The real problem is with using cut corners. Many companies and schools taught different techniques of making 90 degree turns with traces. I was taught to use the Xacto knife to cut half way across the trace, before "bending" the tape 90 degrees to make a corner. That eliminated a messy looking corner produced then the trace is cut all the way across, and overlaid with tape at 90 degrees to make the corner. That produced a radius of about 1/3rd the width of the trace. However, such corner cutting takes time, and it's much easier to make sweeping turns, which is what I did on this PCB. This also has the advantage in RF where it produces shorter trace lengths than with corners. However, none of this is important for this PCB. It was designed for the IBM PC ISA bus, where the highest frequency it might encounter would be about 14.3 MHz.

Agreed. I should have said "impedance bump problem" instead of "reflection problem".

You bet. Interesting history as some might say.

?-)

On Mon, 22 Sep 2014 23:56:33 -0700, josephkk Gave us:

I remember 4X layout work, and the first XT and 286 PCs with AutoCAD for doing 2 layer printer plotted 4X artwork (we were small and could not afford UNIX workstation class CAD hardware back then).

We had our own camera in the engineering lab, and could send production ready photo-resist masks, and gerber files to the PCB house, saving those costs, which back then, mattered.

Then, some idiot formatted the 10MB XT drive. Oh Joy.

A 4.7Gb DVD-R would've mind blowing back then.

It wasn't *SO* long ago that you could set a 600Mb CD-RW formatting, and go for lunch while you wait.