How to be (electronically) Daft and Clever at the Same Time?

“Is it possible?” you might ask. I’d have to say that in my opinion, not only is it possible, it’s normal; and it’s the prime reason why I didn’t volunteer for membership of the human race; personally, I’d rather be in the Oxford and Cambridge boat race, and I can’t swim.

“What’s he on about now?” Well, it’s just a sneaking suspicion, you understand, but it seems to me, that the brainier folks are, the less sense they have. Does this sound horribly familiar? Well, let’s stick with our usual ground; it is supposedly an electronics blog, after all; and how did this ramble come up at all, you might wonder?

It came up, unsurprisingly, with an amp. It was an Arcam Something-or-Other. This gear is so expensive that it’s difficult to find out exactly how expensive it is. Let’s just say they’re likely to charge ground rent on the dealer’s doormat. Oddly enough, I had another reminder, a few years ago, of the ‘lack of sense’ brigade for almost the same reasons, but from utterly the other end of the market spectrum; it was a little Laney guitar combo. If the Arcam was at the covered end of the market, the little Laney was definitely at the other end cleaning out the latrines. But the thinking behind them was disturbingly similar. It’s all around the ‘new is better’ philosophy. This also, in a round-about way, could be read as ’choice is bad for you’,  kind of ‘better’.

Virtually all the technology we might find in computers, mobiles, games consoles etc, is called ‘surface mount’ and is the successor to ‘through hole’ technology. A surface mount resistor (say a 603) is 600 thousandths of an inch long and 300 thousandths of an inch wide. That’s not very big. A 120 pin microprocessor chip, you could fit on a 10 pence coin. That’s not very big either. Without these things, computers, laptops, mobiles and all the rest would not exist. Depending on your point of view, that might be a blessing or a curse, but the point is that the purpose of surface mount technology is to be small. That’s it, ultimately. 

Now, back to the Laney. I opened this combo up and searched around for the amp. At first thought it was a wind-up. At one end of the amp was a pcb about as big as the palm of my hand. And the rest of it was a desert.  They’d miniaturised the whole amp down to a six inch square piece of pcb. In fact, taken as a whole, this amp that was in a usual- sized combo box, could have been fitted comfortably in a small jiffy bag; but for the fact that we needed speakers and a transformer etc. Considering that power electronics are happier with the space and bulk to dissipate the heat generated, the idea of cramping a bagful of this stuff in the corner of an amp that  has room-a-plenty to do it all comfortably and make service and repair that much more accessible, broaches the question “why?” And, uncharitably, ‘Daft?’

The answer is “Cheap”. A surface mount pcb is flow soldered (dipped in a bath of solder), populated by a pick- n- place robot (that puts the bits on it) and it’s more or less finished. However, try desoldering after a fault develops. The tracks (copper interconnections) are thin enough to peel off with the heat of an iron, (or hot air gun), even the first time, but the second time? Very unlikely you might get a second shot at it. So you send it back to the manufacturer, who might reflow the pcb (take off the components and redo the whole thing) or sling it in the bin, because the copper won’t stand a second go.

Make no mistake, the folks who design this gear are clever people. But sensible?

And finally to the Arcam. This was doubly strange, to me. Inside was a surface mount pcb. That was most of it. It had a microprocessor on it which did a load of sophisticated protection. Unfortunately, the output devices had fried; so that didn’t work. It also used an old technology in a new package. The output devices were darlington bipolar transistors. Great idea, give a lot of power gain in one device package. But they have a problem, as do/did all power bipolar devices. The control element (the base connection) unlike a mosfet, is not electrically isolated from the primary current path (base to emitter). When they fault, they often clean out the drive circuitry. Not to mention that one device going short will often take out the rest of the output devices. Mosfets often don’t do this, the gate insulated from the Drain-source current path, and being  happy to share out the power between the rest of the devices. The mosfet is a much newer technology than the bipolar, so why use bipolar? Sounds like new wine and old bottles? Well, I, and a lot of other folks also, think they sound better. A mosfet can do some strange things at the top end of the signal. But we’ll leave aside the subjective, for now.

Here’s the ‘Daft’ bit. We have, in a very expensive amp, a surface mount-populated preamp/drive pcb. Not a straightforward repair item, and one that many would refuse to attempt, especially in the state of the one I saw. This pcb ‘state of the art’ (ugh) pcb drives the (very old school) bipolar output stage that in a fault situation is likely to get obliterated. This is a ‘shove new insides in the old box’, and for what reason? Somebody has a new ‘electronics design software’ package, and has looked at it with the regulation hi-tech blinkers. Only a guess.  

A lot of upmarket gear also trades on the ‘made in uk’  boast. There should be a difference stipulated between ‘assembled in UK’  and ‘manufactured in UK’. It ain’t necessarily the same thing. Tea time, however, is.

                                  I’d actually finished this piece of silliness, and a little story came to mind that you might enjoy, which is, in a very circuitous way, relevant. Possibly.

I used to have a workshop across the road from a junk shop called ‘Aladin’s Cave’, and would, from time to time, insinuate myself for the odd cup of tea. On this occasion Tony had just been out to collect a piece of junk… errm, equipment; which turned out to be a tv set; quite a nice one that he’d ‘acquired’ at a ‘good price’ and was very pleased with his acquisition. He switched it on in the midst of the mayhem that was eternally ‘Aladin’s Cave’ and nothing happened. At all. I thought that I might repay his long term tea generosity and volunteered to have a look inside, hoping for maybe a blown fuse.

We took the case off and found a half brick taped to the bottom. He’d paid forty quid for a half brick in a nice case.

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