‘Attention Span is Now About’…. erm, where was I????

This is another of those rather daft blogs in which I get to SHOUT AT SOMETHING. Let’s face it, there’s plenty to pick from. So who is it that might be the unwitting butt of my ire? Will they care? Will they even notice?

In reply to the latter two questions the answers are:- ‘no’. And ‘no’. And the answer to the first one is ‘nobody in particular, but GOOGLE and HOTFROG will do as the whipping post’. Now I have your full attention (all eight seconds of it) we shall investigate the reasons for this jacking up of my blood pressure.

I received in a circular from Hotfrog (who must be a subsidiary of Google, because everything is), the salutary bit of information that ‘the attention span of the average human being’ (whoever that is) ‘has now shrunk to eight seconds.’ Or something distressingly like that. Effectively, this means that we are generally educated to be up to writing a cross at the bottom of an IOU that we can’t read. About the same as a goldfish, except that we still stay ahead of them by being able to write the cross at the bottom.

The degree of concern shown by these folks who were happy to disseminate this depressing fact was….. none at all. Their concern was entirely that business would have to lower it’s marketing sights in order to continue to sell stuff.

This concern I interpreted in this way. That if you’re selling breakfast cereal your advert says ‘BUY THIS’. If you might be selling mobile phones your advert says ‘BUY THIS’. Maybe you’re selling a car? ‘BUY THIS’. Words of three or four letters should be enough for anybody, so long as they’re in primary colours But not for somebody who wants to think for themselves.

This is no great direction for the evolution of the human race. Personally, I take solace in the fact that the entire ‘digital domain’ could disappear in an instant.

We would really need to be able to think then. It will take us a lot longer than eight seconds to learn to do that, though.

My little blog only exists to blast at bullshit. A little knowledge is great piece of armour.

Tea time.










Binson Echorec…more of the same

The story so far ……

We were left in Dracula’s castle with the blood sucking tortoise attacking (in slow motion, obviously). Meanwhile, back at the ranch, Butch Blair and The Sundance Cod were fighting it out at the Oh Dear! Corral and……….what am I talking about?

Here’s a nice picture of a Binson Echorec. To anybody of a musical disposition, this is as calming as a nice Constable (artist not policeman).

This bit of it is pretty much the same for all Binsons. Back on the subject of half-century old Echorecs that have been stored in the coal shed forever, this picture shows another reason not to switch it on. The reason given in part one of this, was danger of electrocution. Coupled with that, there is also the possibility that you could render the poor thing a pile of scrap. If the heads have been unwisely shifted about, they can shred the recording material from the disc, which means you get a lot of noise and not much echo.

If get our bearings from the pic, the heads are positioned around the disc edge, as shown. They should not rub (or touch) the disc; so this is the subject of this little diversion. If you upend the unit you will find the bearing cylinder sticking out under the top plate. There are two screws on it. One big one at the bottom (which you will hopefully not need to touch) and a slotted head screw in the side. If you unscrew this a few turns, the disc will be removable, and from the top you’ll see the tube that the disc bearing fits into. You need to clean off all the grease/oil/crap from the socket and also the disc shaft. Blast contact cleaner in the socket and onto the shaft. Then you need to replace the oil you’ve taken off, using the stuff supplied in the little bottle in the clip. If that’s not there, a light oil like say 3-in-one, will be ok.

Replace the disc, and gently move it up and down while tightening the screw you slackened off earlier. There’s nothing more to do with the disc, but the interwheel/idler drive might need attention. That’s the rubber drive wheel marked in the pic. The problem with this is that it rests on the capstan and over a long time creates a notch in the rubber surface. If that has happened it will sound like Pavarotti sliding over a cattle grid. Whatever turns you on, I suppose. The best remedy is to throw the wheel away and fit another. Dead easy, just one screw holds it. But, if you can find one, it will cost all your limbs and a few of somebody else’s. Probably. Here’s a couple of alternative possibilities.

If you know a feller handy on a lathe, you get him to take off a few thou (thousandth’s of an inch) from the edge of the wheel until the dint in the edge has gone. The best way to do this is to freeze the wheel. Then it doesn’t distort during the turning process.

The other alternative does work, but it takes a fair bit of patience, and you can’t do it until the heads have been set up. You run the disc and place a flat needle file gently on the edge of the rubber wheel and keep it going until you can’t feel the ‘bump’ as the indentation passes under the file.

To set the heads it’s best done with a scope, but can be tolerably ok without. All the following is done with the disc stationary. You need a small spanner, about 8mm if I remember right. There is a hexagonal mounting pillar for each head; you look down at the gap between the disc face and the head face. A torch underneath helps. If they touch, you need to back the mounting pillar off with the spanner, clockwise, just a tweak. Then you need a piece of thin paper. You slide this between the head and the disc face and then tweak the pillar back again until it just (only just) traps the paper. Remove the paper and you should see a slight gap between the head and the disc.

You go through all the heads like that. After doing all that (and having replaced the wiring as in part one) you can switch it on.

Then you’ve gone far enough to find out whether it works or not.

Tea time.

Binson Echorec…..well, nearly.

Around the late ’70′s-early ’80′s the Binson company built units for Guild and Sound City; both very big names of the time. Don’t quote me on the dates. According my history books Oliver Cromwell lived next door to  Nova Scotia.

There was a very considerable difference between the gear with ‘Echorec’ marked on it and those we’ve just mentioned. The Guild and Sound City versions were transistor machines and Binson’s usual designs were all valve. The ‘Echomaster’ was Sound City’s incarnation,and that’s what this is.

You have to admit, it looks very cool; they all do. I think they could have knocked one up out of washing up liquid bottles, and they would still have looked cool.

Although this model is so different from the usual Echorec models, in some ways they are exactly the same. With many of the same problems. The idea behind any mechanical analogue echo, is that the signal (sound) is recorded via a record head, onto a moving medium; might be a tape loop or a cassette loop of some sort. This sound on the tape then passes across playback heads and this means that the sound will be played back later and at different times from the original sound. There are a variety of ways these repeat echos are processed afterwards, but that is basically the arrangement.

The Binson is different. The recording medium is a steel disc which revolves past the heads, and has a recording surface on the edge. Not many designs use this. Schaller did one, and that’s the only other that I know of. The idea is still the same as the tape, though.

So that’s a very approximate overview. Should you be so fortunate as to acquire one of these brilliant pieces of coolness (coolity?) from your neighbour who has kept it under a sack of spuds for a half century you should be very cautious about switching it on. Best done with a long stick from behind a wall of sandbags.

The coloured cables are the reasons why. They are the originals and the insulation often rots away, so you get bare copper exposed. I don’t know what the insulation was made from, but it could be a rubber-based material and that would perish, so it makes sense. The high voltage stuff is also made of the same materials. The pic shows the job part-way through. The black screened cables have replaced some of the original wiring, but it was all replaced in due course.

You have to do (or at least visually check) this wiring BEFORE YOU SWITCH IT ON. Or make sure you get your solicitor to check that your fire insurance is up to date. That means the signal cables and the mains/ HT wiring. It’s a time-consuming job before you’ve even thought about whether it works or not.

I’m going to continue with the procedure for setting up the heads and disk on the next blog. Otherwise these things start to look like an unexpurgated big letter version of ‘War and Peace’ and nobody will read it. So what’s new?

Time for tea.

Read a Schematic? A piece of poop.

Let’s face it. It can’t be very hard to do; or I wouldn’t be able to do it. No. Reading one is EASY. You need to be able to remember what a line looks like. And what two parallel lines look like. And what a wiggly line (or a rectangle) looks like. And a triangle looks like.

There are, maybe, a dozen or so symbols that represent components: resistors, capacitors, transistors, IC’s. They connect together with lines. None of this represents where they are in an amplifier, just how one component connects to another. So the whole technique of reading a schematic diagram involves following lines and finding where they go to. SIMPLE. But……

Why do engineers take so long to learn their job, if it is so simple? It’s because the reading is the simple bit. INTERPRETING…..well….that’s something else.

So your line (track/wire) goes to this transistor. Fine. But the amp doesn’t work. Not fine. So what can be wrong? what is it supposed to do, just there? Why is this voltage high? why does this chip put out dc? These are questions that happen all the time, and the schematic won’t help you to solve them. It tells you what connects to what, what the ‘what’ is. It doesn’t tell you what it is supposed to do or why it isn’t doing it. Now that is the hard bit.

I read some time ago that ‘a good engineer doesn’t need a schematic’. It was written by either a hyper-optimistic or woefully inexperienced bloke. Although I wouldn’t argue with the fact that we can repair without schematic diagrams, (carrying around a lot of generalised ones in our heads) I would argue that the customer will be charged a lot of money for the privilege, and that is an irresponsible attitude on the part of the engineer. It will take much longer without our trusty schematic. Which is why I frequently rail against secretive attitudes of  amp manufacturers.

Tea time.


The Vox AC 30

“You’ve done this one already” you might say. True, but there are a lot out there and they keep turning up at my workshop. This particular one was another result of a ‘GAS attack’ of Marc’s. He does suffer, does that gentleman. It did throw up a few issues that might be of use to those unwary enough to delve into these things. It also broached the subject of just how much we should pay for…well, anything, really.

 So, for a start what do I mean by that? Well, the bits inside an amplifier cost the manufacturer 77 pence. (Approximately.) The folks who put it together are mostly robots and their oil bill for the century is about the same. Or it’s made in China or somewhere else they eat rice and where 38.5 amplifiers = 1 bowl of rice. So that is another 77pence. (Approximately.) That works out to 2 pence per amplifier. Even given the benefit of any doubt that might be lurking, the amp cost a bit less than a quid to produce. (Approximately.)

Now we get to the really expensive bit. For every bloke/robot in the shed actually knocking these things out there are at least 174 blokes in designer sunglasses selling ‘em. It’s called ‘Marketing’ and that’s where our money goes. So we buy things to be persuaded to buy things.

This is the underside of the power section of the Vox AC30. Pretty much original but the mains transformer has been swapped in the past.



This was after I got hold of it. I often use solid copper ground rails where they once relied on the metalwork of the chassis. The contact to the frame deteriorates, and you can clean them up as much as you like in a year or two they’ll be back causing you problems again.

The output valve bases were replaced with lacquered ceramic bases. They hardly ever track and the gold contacts are very robust. Anyway that’s all pretty specific, but the generality interest comes with actually switching on an old amp that has been in retirement for a long time that has a valve rectifier. Don’t do it.

Here’s what really needs to be done. Take the rectifier valve out. Solder a couple of diodes (say 1N4007) to the valve base. The sides with the silver band are connected together and soldered to the HT output (the single wire that goes to the first capacitor) and the other sides go each to the transformer connections. Then put a capacitance meter across that first capacitor. An ohm meter reading is better than nothing. This one was a short. Had I switched that on, the rectifier valve would have blown and it could possibly have taken out the mains transformer. Best to be cautious. As it happened the rectifier valve also had a short, so that would have been a total disaster. You can check out the whole of the amp leaving in the two diodes. If anything nasty happens, your 20pence diodes will survive, and your nice new £15 worth of GZ34 probably wouldn’t.

Tea time.



AER Domino- the silent amp

AER Domino

Expensive and doesn’t work

Un…..fortunately…..we have yet another example of a company on the Unofficial Secrets list. This means that their designs are so clever that nobody else should be allowed to repair them.

This could also mean, possibly, that it would be unwise for them to let anybody in there who might know what they’re doing. Because they might just sus out that these designs are not particularly clever, nor are they especially well manufactured, nor do they work all that brilliantly well.

It has to be said that this amp was devastatingly silent in operation.That’s because it didn’t work at all.

TDA7294 power amp chipsThese two little black blobs are TDA7294 integrated circuits (chips), and these are the devices that make this little AER amp make sound. Each device is rated at 100 watts rms dissipation, so should, on the face of it, be good for 200 watts all told. Each chip supplies one of the speakers. So far so good.

The property that limits the output of these chips (and also causes them the most problems, often) is how fast they can get rid of the heat that is developed in pushing out power to the load (speakers). These are exactly the same chips as are used in the Marshall AVT series amps. The AVT 150 uses two of these in bridge mode, which is something I should cover as we go on. So back to that in a bit. The difference in design is not great, the major difference being that in the Marshall amps the chips are built on a separate pcb and is fan cooled; which is a big plus in getting rid of heat. This why the Marshall AVT150 has the same two chips rated at 150watts rms and the Domino is rated at 50 watts lower. In the Domino amp the heat sink is alloy and has no forced draft cooling so the heat dissipation characteristic is much lower.

A major reason why this amp decided to self destruct was a result of the heat sink integrity. The stuff that is used to ensure that the heat is carried away very quickly is ’heat transfer compound’. This grease-like stuff you apply to the heat sink/ power amp chip surfaces and it keeps the temperature gradient across the junction of the heat sink and chip surface to a low value. Un…fortunately this stuff can harden with age and can become a heat insulator; so it has exactly the opposite effect as it was supposed to have when first manufactured. If you’re going to get into a big service on one of these things, one of the operations should be to release the heat sink from the chips, clean the surfaces and re-compound the thing.

The fault on this particular little Domino was fairly obvious straight away; a leg had blown off a power amp chip. The fix is to take the TDA7294 out (both of them preferably) and replace them. This is not as simple as it might sound. Desoldering 15 pins (30 if both chips are removed) on a modern printed circuit board is a tricky operation. The reason is that if you get the tracks too hot they’ll peel off. If you don’t do a great job on desoldering, you will pull the tracks/pads off. Also, as the pads are close together there is a possibility of solder bridges. Be very wary of all this stuff. The approach with the least trouble is to take the fixing screw out of the TDA chips and lever it away from the heat sink a little. Then cut all the pins. Resolder the pads before you desolder them. That’s because when robots solder joints they tend to have little tin left in them, which means you are desoldering lead, which means you have to get the joints hotter which means that you might start to lose tracks. Bad idea.

After that you need to make sure you are grounded. With a wrist strap or some such. Static is a killer on these things. The chips themselves are not a lot of money but the job itself is a fiddly one.

Now we get to the hair pulling out stuff. All back together, this amp worked fine on the bench. I ran it up to a decent output on dummy load checked everything was getting rid of heat as it should, and it went out.

It came back. It hadn’t worked at all for Tom. And I put it back on the bench and…..it didn’t work for me either. Bugger. I couldn’t find anything wrong, so I decided to do the whole job again. For nothing, of course. Only engineers are stupid enough to be engineers. I must have said that before somewhere. But it didn’t work. Not a dickey bird.

As this was a produce of the AER Secret Society, I couldn’t find a schematic for it anywhere. (Does the word Samson spring off the page here????) So I downloaded a TDA7294 data sheet. You can find these without much trouble. It at least gave me a bit of a handle, and as we know by now, I really hate the so-called ‘Free Information Society’ mostly because it’s bullshit. So I will go to a lot of trouble to show these folks up for what they are. Anyway, onwards and….whatever…..

The data sheet showed that two of the fifteen pins (9 and 10 if I remember right) were used as a standby and a mute. If the mute pin had a low voltage to it the amp wouldn’t do anything. If the standby had a low on it, it remained in standby. Well I had to draw out a bit of the circuit, but I found that it was just a capacitor that charged up to put a delayed high to the mute pin. In this pic the grey/black cap to the right of the red probe was leaking badly. This is common to both TDA chips and so mutes both amps at switch on. Un….fortunately….if the cap is leaking the mute remains on. That took some figuring out, no thanks to the tech support of AER.

Just as an aside, I mentioned ‘bridge mode’ earlier on. Many power amps have a bridge mode setting and you need to use it with a lot of caution. The arrangement uses two power amps. In a stereo power amp these would each drive a separate load; the amp drives into one side of the speaker, and the other is connected to ground. In bridge mode, one amp drives into, say, the positive speaker pin, but the other instead of connecting to ground, is driven by the other amp. Unless the phase of one amp is reversed, the result of that would be nothing at all. But one amp has its phase reversed (in the preamp section) so one amp pushes when the other pulls. The result of this is that the power of both amps is summed in the speaker and the power out is equivalent to the sum of the power of both amps.

It’s not impossible to run one of the amps into a short in this arrangement. Hence the gentle warning.

Time for tea.


The Samson Success Story

It should read, ‘The Samson Success Story-Never Give a Sucker an Even Break’….but I couldn’t fit it all on.

Once upon a time (yes, you can put on your bedsocks and the nightcap with the nice bobble on it)….once upon a time, people who made things used to have a concern about their being able to get them fixed when they burst into flame, or what have you. At the times we are considering, laudable manufacturers of the quality of Leak, Quad, Radford, Mullard, (and Fender and Gibson and Ampeg and Selmer and on, and on) would credit their customers with a bit of sense and supply a schematic diagram with their hard earned purchase. Some would even stick the diagram in the amp somewhere.

Nowadays, of course, the gear is much more complicated. And also, it’s much more complicated. Apart from that it’s much more complicated. And also, well, it’s much more complicated. Don’t ask me why, though. Anyway, because it’s so much MORE COMPLICATED, the poor stupid cretins like us (who were after all, daft enough to buy the stuff in the first place) shouldn’t be allowed the temptation to want to get it fixed. So, these days, not only will you be unlikely to find a schematic diagram supplied, you’ll be lucky to find one on the same planet. Because, obviously, it’s far TOO COMPLICATED.

The last bulletin on the Samson 308i had me tearing my hair out and donating it to the cushion manufacturing cottage industry. They would be thin cushions, I’ll admit that. I didn’t fix it. I’ll admit that as well. BUT.

I assembled 61 data sheets, drawings, specs, sketches. I also drew out a significant chunk of the circuit. All this took a long time, my only motive being bloody mindedness. I love the idea that the people who make these things take responsibility for their doings. It doesn’t seem to happen very often currently. Probably too clever, eh?

Here’s an aside, and a plug for Marshall, as it happens. A gent called Simon wanted me to take a look at hand wired 20 watt head that had faulted. He’d paid something of the order £1700 for it. (Yes I got the noughts right). The mains transformer had blown, I gave it him back and told him to get in touch with Marshall, because it was a bit over warranty, but not much. They shipped it free of charge, and repaired it in the week. Hat’s off to those gents (and ladies). I ran up a flag to mark the occasion.

Anyway, back to Samson, who I don’t run up flags for.

The result of all this delving (which would have taken me half an hour with the schematic) was to show up the fact that there are two other devices in there (other than the main Fairchild switchmode chip) that supply the low voltage regulators for the preamps and 5volt digital supplies. One is a TNY274-280 off-line switching chip, and the other is a Viper 28 which is a pulse width modulator chip.

I replaced these and all the original repairs I did to the main switching STARTED WORKING!!!!!

Walla! Fixed! I assumed from this that the low voltage power supplies enabled the high voltage/current stuff and therefore nothing worked until they were all happy.

Unfortunately, this will not help you to fix one yourself. They are bad news to work on with everything surface mount and very small.

But it just shows that you can crack these codes if you are bloody minded enough.

Time for tea.

Samson XP308i Expedition. Lost in the upper reaches of the Unpopo. I wish.

This a nice picture of a Samson XP308i.


Shortly after I’d dropped it off a cliff. Or maybe just before. In this case it wouldn’t have made much difference because it didn’t work.



I know this might sound Neanderthal, but I don’t like switchmode power supplies. Uggy-wuggy-grunt. There you go, I am Neanderthal. I’m Stone Age enough not to run my business on bullshit and subterfuge, which currently shrinks my playing field down to the size of a postage stamp.

So what is wrong with switch mode power supplies? More to the point, what is a switchmode power supply? And also why is it? And what is the alternative?

All these riveting issues you’ve fallen asleep over, will be rivetingly detailed in our next week’s riveting issue, called ‘How to sell something you haven’t got.’ No, not really…… onwards and inwards.


This is a picture of the main bit of a switchmode power supply. The finned thing is the heatsink, upon which is screwed a switching regulator (in this case a Fairchild  KA1M0880B power switch which is the nearest device you see screwed to it. The next one along is a high current diode and the one furthest away is a mosfet transistor which beefs up the output from the switching regulator to supply the amp circuitry. There are few different ways to design these things but the idea is that the mains input is directly rectified to produce something like 330 volts dc. This an impractical voltage as it stands. It is too high to do anything with for a semiconductor amp, and also, d.c. is not readily manipulated to produce the various different voltages that the amp needs; in this case probably +15 volts, -15 volts, 5 volt digital supply, and then maybe +30 volts or so, and -30 volts ish.

So we’re starting with a voltage from the supply that is way too high, and we can’t easily modify it.

An orthodox power supply has an isolating mains transformer. The primary side is connected to the mains supply, and there is no direct connection to the electronic gubbins in the amplifier. The secondary side of this transformer has several windings (or coils of wire, if you like) wound on the same lump of metal as the primary winding. By having various sized windings, many different voltages can be available, and the whole idea is relatively simple.

The switchmode idea has no isolation from the mains, it goes straight into a bridge rectifier and comes out of that as high voltage d.c. as we’ve already said. So where do the voltages come from? Well, the switching regulator we mentioned ‘chops’ the d.c. and produces a high frequency (in the Samson case 75 kHz) and this can be transformed to give the various voltages by much smaller transformers, because of the high frequencies involved.

So what was wrong with the traditional power supply, that we need to do away with it?

One of these things you might have already guessed. Wait for it……..a switchmode……

IS CHEAP!!!!! Yayyyy! Even including the little transformers a switchmode like this is unlikely to cost the manufacturer more than a few quid.  On the other hand the ‘old’ transformer arrangement is probably ten times the price to build.

Another big plus for the switching supply, and especially in the case of toy p.a. stuff like this Samson is, is that it’s lightweight. A traditional power supply is a lot of things but it is definitely not that.

So why don’t I like them? It’s fair question. Might it be that I don’t like anything less than fifty years old? Well………….alright, you got me there. But I do like ideas that save the good old planet’s resources, and it does save a lot of copper and steel by not building a big transformer. But……………………

Switchmode has many problems that I don’t like. First (whatever they say) I see a lot that are blown to hell. They have many protection devices in there (overvoltage, overcurrent, overtemperature, overblown claims of longevity…… well maybe not that) but they still seem to hit the rocks very regularly. Second, there is no isolation between you and the mains supply. I Don’t like that. Third, it doesn’t have the same inherent filtering of mains noise of an isolating transformer. Fourth, as with many unnecessarily ‘complicated’ things there is a lot more to go wrong.  Fifth, (again, whatever they say) the switching noise generated inside the unit will leak into the mains supply. We don’t need more crap in the mains that we already have. Just one of these things, well, ok; but a hundred thousand, say? It just seems to be a step in the wrong direction, to me.

I’ve actually led you astray, here. (So what’s new?) Because this Samson Expedition thing I haven’t fixed. Yet.


This is where I get into another ‘Pet hates’ tirade. The pic shown is of the sheaf of paper I have so far assembled in the interests repairing this amplifier. Why did I need to do this? It’s because of the increasingly secretive nature of the so-called ‘free information society’. After spending several hours on the web searching for schematics for the XP308i, I was forced to draw the conclusion that there isn’t any.

I’m sure there are a bagful of bullshit reasons for this, but the obvious one, you rarely find mentioned. Samson don’t want these things repairing. Just a guess, you understand.

Being a very bloody-minded person, that, I find is a great encouragement to figuring out what it’s all about, how it works, and fixing the damned thing. I’ll bring news of this job in due course, but just as a hopefully useful aside, to anybody unfortunate enough to get stuck inside one of these:- Beware of applying too much heat to the tracks, they’re very flimsy. Check that you have 330 volts dc out of the mains bridge rectifier. Check, that from pin one on the KA1M0880B(that’s the nearest pin to the edge of the heat sink) to the negative pin on the main rectifier, you have a significant ac signal. Don’t use a grounded scope (or anything else grounded) on this switching part of the circuit, as it is all referred to virtual ground. If none of this makes any sense, probably best not to go there.

We will be back on this amp, we will fix it, and I will let you know how it was done. And hopefully Samson, and all those of a similarly secretive fraternity will get it as a sound kick up the arse.

Time for tea.


Fender Deluxe reverb

Marc is a nice bloke, and an intelligent one, until it comes to the issue of GAS. When this rears its bankrupt head, it’s true that most of us of a musical persuasion lose any grip we might ever have had on the excuse for reality that we have forced on us.

For the uninitiated, GAS is the acronym for ‘Gear Acquisition Syndrome’, although you would have lived forever at the bottom of a well, not to have come across it.

I have a Stetson hat and welding goggles for my GAS attacks. “How does that work?” you might wonder in an idle moment under the duvet. It goes like this. The bloke who walks into the music shop with welding goggles and a Stetson with the brim pulled down to his feet, is me. I stare at the floor, ask for my bag of strings and get the hell out before anything hanging on the wall commands me to buy it.

What has all this to do with Marc and his Fender Deluxe reverb? Well, he does seem to buy a lot of things that end up in my hands being fixed. The latest being his nice Deluxe that didn’t sound right when he cranked it up. Bearing in mind that the amp is only (but worthily) rated at 22 watts rms, might he just be asking for it to do more than it reasonably is capable of?

It was a strange fault, and this is why I’m jotting about it. Strange, but in essence, simple; when you know what it is. The same could be said about Blackpool rock, Dark Matter, quantum physics, and the Dyson vacuum cleaner. All simple after it’s been done; by somebody else.  

If somebody complains about something not sounding right, crossover distortion and intermodulation distortion come high on my list of things to look at, because they both have symptoms not easy to describe. If your amp sounds like a bear’s arse being filed down with a hatchet it’s not a subtle thing. That depends on your degree of sensitivity and whether or not you happen to be the bear. But the subtle faults are notoriously hard to describe.

Crossover distortion often makes an amp sound ‘weak’. If biasing is overdone on the output valve control grids, the positive and negative -going signals cross over badly and you get a weak sound and early clipping, so lower power output.

Intermodulation distortion is when your nice guitar sound gets mixed in with some other noise like, say 100hz buzz (poor smoothing, check the reservoir/smoothing caps) or 50 hz hum (check the hum balance if you’ve got one).

This was neither of those things, and in the first place, didn’t exist at all. One of the things you figure out early on in your engineering training is the effect a bench has on all things broken. It often makes them work. Briefly. So the MesaBoogie just brought in by a suicidal musician who watched it disappear under the wheels of the 8.24 from Paddington, is shovelled onto the bench where it rests for a second or two, before producing the most glorious music. So he says “It never did that for me, after the train ran over it”.  

Extreme case, I grant you, but it happens all the time. Back to Marc’s Fender Deluxe. It was perfect. These things just look right on a ‘scope if you’ve looked at scopes for a long, long time. So he had it back. No fix, no charge. I’d be very wealthy if I charged for the things I didn’t fix. You know, like the microwave in the Aspidistra Hotel in Llandudno. I’ve never been there but it’s the same principle. Just send a bill somewhere if I get a bit short of the readies. I’d probably do well in the tax office. Anyway, he got it back home and it was just the same. I was getting the ‘Black Hole ’ feeling about it.

To cut an already tedious story to the slightly less boring. 

It turned out that many(!) if the power valvebase contacts had been poorly manufactured (it had to be a manufacturing fault, because the thing looked nearly new even though it wasn’t) a bit of a jiggle around in the car, and the screen grid contact on one of the 6V6′s open circuited, and resulted in that particular valve putting out a fraction of its share of the power. I slotted a watchmaker’s screwdiver down each side of all the valve base contacts to tighten them up, and everything was, and still is, hunky dory.

Often the repair is far easier than the figuring out of the what it is you should be repairing.

Tea time.

How to Make a Lot of Money Very Quick

A notion, at which you might shudder as it slithers out from under the slimy rock next to your settee, is fairly pre-puberty in its tower block subtlety. It has a mathematical probability approaching certainty that, considering the glut of advisors on this very subject, nobody is telling you anything that might be remotely useful to your acquiring your first million. Or first fiver, for that matter. Otherwise we’d all be rolling in it. Money, that is. You can procure, with no more than garcon-esque twitch of the little finger, enough paper to start Guy Fawkes off. Just so long as none of it looks like a ten pound note.

So, just to clarify.

First: anybody who is willing to advise you free of charge, is going to send you a bill in the next post. Except that you can take money off folks a lot quicker these days with a PayPal account. The free gift offered will not, strange to say, be a brush to paint the red numbers in your current account black. More likely it is a wobbly plastic dinosaur that makes your cornflakes taste of urine. Maybe that’s what they taste like without the wobbly plastic dinosaur, but I’ve never had a box without one so it’s hard to tell.

A simple litmus test is all we need to prove the aforementioned pecuniary point. First of all you need to locate a barrister, solicitor or some other member of that august body. You can tell an august body member by its shape; they’re the ones that drop their leaves (and anything else that may give a career leg up) at the merest mention of an annuity. You may need to nip back to the rock next to your settee to pinpoint one of these members geographically, however.

“How does this test go, then?” you might wonder. It is very, very simple. The whole profession is very, very simple so that should come as no surprise. If you really want to join it you need no more than extraordinary memory for things that didn’t matter four hundred years ago. And a completely vacuous brain for anything that might, even from a vast distance, seem like it might make sense. Back to the test.

Our barrister, we will conjecture, is progressing along the street towards us. They don’t walk. This one has just emerged from a litigation meeting and is swinging from the bells of Notre Dame but without the bells. This is because they are paid by the second in gold bullion and insist on it in cash. Or if it looks like a scorpion poised to stick something nasty in you, this one is very, very important and just can’t quite get its nose far enough away from its arse. Back to the test. You ask it the time. The answer will be


This will be announced without reference to any form of timepiece, but will certainly be accompanied by vigorous scratching’s on a triplicate pad. The following morning, a buff-coloured watermarked manila envelope will fall on your doormat. This will contain a bill for £746.73 and a statement of the time “3.24 pm.”

Now that’s How to Make a Lot of Money Very Quick.