Jacques Mattheij

Technology, Coding and Business

No User Serviceable Parts Inside

When I was a kid and for the first time interested in electronics (to me that meant anything that did not involve just wires, switches, batteries and lamps) we were just coming out of the ‘tube’ era in to the solid state era.

So naturally, ‘tube’ hardware was to be found left, right and center, and any clever big city kid knew the garbage collection days for the whole place by heart.

On Tuesdays and Fridays I’d get up really early and walk along the garbage route to see if I could pick up any interesting bits of hardware. Typically a scavenging run would yield a radio, a TV, a gramophone or in a rare case of luck a reel-to-reel tape recorder. Sometimes even more than one piece.

I’d haul these home and put them in the basement, either for dissection, or for repair. In some cases the circuits were printed on a piece of paper inside the box, more often than not you’d be left to your own devices to figure out what was going on.

Repairing tube circuitry is not all that difficult but it is quite dangerous due to the high voltages involved. I got zapped with some regularity and I learned how to move very careful near the various parts, especially the ‘top’ connectors to some of the more powerful tubes were mean!

Typically I’d open up the box, plug it in and start scanning for obvious defects, such as a tube not being lit up. From ‘failed’ experiments I had boxes full of various kinds of tubes and usually if a tube was blown I had a spare handy. Take the old tube out, put the new one in, plug it in and bliss, someone’s garbage became my treasure. If the repair wasn’t that easy I’d try to figure out what else might be wrong, sometimes it would work, plenty of times it didn’t (or the patient died on the table due to a dropped screwdriver or something like that).

If you’ve never seen the guts of a really old tube based piece of electronics let me try to describe it to you: The components are all soldered to a metal chassis with the tube sockets and a bunch of helper boards as the main supports for the rest of the parts (mostly capacitors and resistors). Heavier parts such as transformers are typically bolted to the chassis.

Here is a nice example:

Like that the ‘circuit’ is simply made up by the parts themselves, usually with a bit of wire thrown in in case a component leg isn’t quite long enough or awkwardly placed. Components were so large their values were simply printed on them.

Fast forward 5 years. The solid state revolution has changed things completely, now circuit boards dominate the electronics, the compact cassette has been introduced and a typical piece of equipment has only 1/10th the volume dedicated to the circuitry. Color television became common (sure, we had those with tubes as well, but very rare). You can still trace the wiring on the underside of the boards so at least that is still possible. The components have already started shrinking, as you can see the resistors on the board are small enough that printing a value is no longer feasible so a color code is used instead.

Hybrid solutions (for instance, in TVs) were common still but as higher power and voltage semiconductors became available the tubes were to be found further and further down the circuit diagram, until in the end only the picture tube remained.

Another 5 years and thin film circuitry started to show up everywhere. These were little modules soldered in to the rest of the circuit board that had their own function and could be found in different types of equipment unchanged. Sometimes these little circuits were quite elaborate, with a hundred parts or more on a tiny little board, more often than not caked in some goop so you couldn’t re-use the parts (or figure out how it worked). Circuit boards became more complex, traces on both sides were sometimes used.

5 years after that and all these thin film parts were gone again, replaced by little black rectangular units called ‘chips’, or ICs (short for integrated circuit). Double sided circuit boards by now were very common, and more and more complex, getting ever harder to trace, and of course any efforts to trace the circuitry would always stop at the edge of some chip because if you didn’t know what was going on inside them you didn’t stand a chance of opening them up and tracing in there (short of having industrial espionage gear). To make matters worse manufacturers would sandblast the markings off in order to protect their designs from being copied.

The parts inside the chips were no longer discrete components, they were all grown in one go on a slice of silicon and packaged in a house many times the size of the actual circuit.

Somewhere around this time I saw this sticker for the first time:

No User Serviceable Parts Inside

It marked the end of an era. Even the fuses had gone away, and circuit boards were no longer to be inspected by mere mortals with a technical hang-up. You had to go to a repair shop. As a rule that sticker came smack on top of one or more of the screw holes that gave you access to the innards of the equipment, and penetrating the sticker was a good way to void any warranty.

Of course I happily ignored the warning on the sticker and tried to do my best but there definitely was a downward trend in being able to fix stuff simply because of the level of integration and the application of custom rather than standardized components.

As integration progressed chips became more and more complicated to the point where the functionality of an entire device was contained in very few or even just a single chip, and surface mounting required ever more complex soldering gear. It can be done, but it’s tricky and hit-and-miss. Funny side effect of surface mounted devices (or SMDs) is that the color code on resistors was replaced by printed text again (because SMD’s have sides, but hole-through resistors do not).

Replacing circuits became cheaper than repairing and today only real fanatics (aka hobbyists) actually have the time to trace a circuit fault on a board to replace an individual part. The usual reason is that the hourly rate of a competent technician multiplied by the MTTR (mean time to repair) of a given circuit is higher than the cost of a new board, especially because those ‘custom’ chips typically were cheaper for the manufacturer but unavailable to the people trying to fix stuff.

So repairmen became functional unit exchangers. One industry in which this led to some weird excesses is the automotive industry, where a circuit that probably costs the manufacturer just a few dollars to produce gets re-sold as a repair part with an absolutely insane mark-up. After all, what are you going to do, spend four weeks trying to reverse engineer the secret sauce from a broken component in order to fix it? I didn’t think so. It’s always easy to make money on a captive audience.

I understand that the enormous avalanche of consumer electronics would never ever have been possible without the solid state revolution and the subsequent avalanche of integration improvements.

But I still can’t help to long for the days when stuff was always fixable and that dreaded sticker didn’t exist. Throwing all these perfectly good pieces of gear with maybe one broken transistor or capacitor away as garbage somehow doesn’t feel right.

And even today I’ll try anything I can to fix stuff rather than to toss it, even if that may not make economic sense and even if it doesn’t always work it definitely makes me feel better. <!– 186 –>

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