and this goes back to the earlier comment I made, namely that these solderless breadboards are unsuited for anything. I didn't say that they are unuseable, though.

First of all, however, I have to disagree with your general statement implying that they are unuseable for digital circuits. I personally believe that they are more useable with digital than analog circuitry, though that's with the caveat that they're more effective with impedances in the range between 100 ohms and 50 k-ohms than with lower or higher impedances, the latter because of the high (~5pf, IIRC) contact-to-contact capacitance and the former because of poor contacts and long power and GND paths.

Both analog and digital circuits are negatively impacted by the dearth of power and ground paths available. Frequency is a major factor, but digital hardware is not likely to be "hurt" by the often excessive wire lengths so long as frequencies are under 20 MHz and signal currents are under 20 mA.

On small boards, such as the one shown in the O/P's pictures, there are only two power and ground rails. This causes "issues" for analog circuits, because references and returns have to share those rails, the contact and path resistance of which is considerable. The two boards I bought in the '70's are both large. I was subsequently given a small one, but none of them proved terribly good, though I have, from time to time, used them to demonstrate (or to "try") a simple circuit behavior.

One of my long-time colleagues, who does like these boards, even went so far as to build a circuit board that replicated the connection pattern of the solderless breadboard so that, having once managed to attain reasonable functionality on his breadboard, he could replicate the circuit on a board to which he could solder his connections in order to fabricate a more permanent version of a circuit. The salient point of that is that solderless-breadboard implementations are fragile and unlikely to behave similarly on separate occasions unless they're carefully constructed and protected from any sort of interference/damage between uses. Meticulous constructions, with wires cut to precise lengths and carefully routed for effect, sometimes allow repeated use, but often, inexplicably, behave differently than expected, after sitting on the shelf for a time.

I've found that these boards can be made to work quite adequately, for small digital circuits, of, say, 16-20 IC's. The first thing I built on one, one with an integral power supply, was a pair of 16-bit counters with an adder and an LED display, mostly in 'L' technology. It worked fine, though I was concerned about the power supply. That was the last time I attempted to build such a large circuit on a solderless breadboard, however. I found, along the way, that it took more than twice as long to build the circuit on the solderless breadboard than it took to build it using wire-wrap, though the wire-wrapped version, which I ended up building anyway, was MUCH MORE STABILE in its behavior.

I've often said that where you sit determines what you see. In my work, I've had multiple reasons never to use one of these boards, aside from simple trials or demonstrations, and certainly not for anything that has to work the next day. I've not denied that is is possible to construct properly working circuits on them, though it seldom is done. Clearly we've had different experience with respect to this type of product. You, Kai, seem to have found them adequate for your work. I've not found them adequate for mine.

I've used these boards to demonstrate power supply circuit behavior, starting with rectifiers, from 60 Hz, or relay drivers, and sometimes multiplexed displays. It's not easy to use them as modules because there's little provision for connectors of any sort other than single-in-line types. Because of their inherent fragility, though it might be tempting to do so because of their relatively low cost, the small boards suffer from a critical dearth of supply distribution features. With the larger boards, it is tempting to attempt to use the somewhat less-scarce supply distribution strips, the temptation is great, to use them for both return and reference paths, which works out badly for amplifiers, as they will amplify the voltage error introduced by changing currents in the relative high-resistance ground rail.

One other inherent problem presents itself. Without the use of those wire-wrap sockets to which I referred previously, it's not easy to attach instrumentation to a circuit. Since one normally wants to "try" a circuit on these boards, it's important to be able to observe their behavior. Without instrument connections, it's not easy to do that. If you want to attach an oscillsocope, a signal generator, a pulse generator, and a counter, a small board becomes too cluttered and probe/cable weight can easily interfere with component-to-board connectivity. Even a larger solderless breadboard is not easy to work with when several instruments are required, some to stimulate the circuit and some to observe/record its behavior. Frankly, these are thorny issues that trouble persons working with printed circuits and wire-wrapped ones as well, but when probe or cable mass can cause components to shift in or even come out of their site, it's no longer fun to work with solderless breadboards. I've even built suspension fixtures to keep cables and probes from extracting compoents by hanging the probes/cables from the ceiling. You can imagine what a 3-dimensional mess that is!

Ultimately, the solderless breadboard is used to "try" circuits that probably will have to be implemented in PCB (if they work satisfactorily). Experience, an not just my own, has shown that solderless breadboards do not provide an adequate environment for verifying function of circuits to be implemented later in PCB. There are too many differences.

RE

P.S. Kai - I apologize for any insult you may have perceived from my remark about frequency. I intended none. I have found these boards to be perfectly adequate for trial and demonstration of line-frequency circuits, e.g. rectifiers, power switches, etc, and other things operating at less than 1 kHz. That's what gave rise to my remark.