Cheap as Chips.

After a fallow season of things to moan on about, again the ‘pro’ world comes to my rescue with its usual clutch of the overbearing, attempting to befuddle and disinform the unwary and trusting. This time it’s Laney.

It’s a tough job to work out who owns what, what owns whom and where you might find somebody who would own up when it goes tits up.

Take the word ‘Mini’ for instance. I used to be able to fix my  mini in the middle of a desert with a screwdriver. So long as I have my handy diagnostics computer and a main dealer in tow, it’s not impossible that I still might, with today’s incarnation. But very improbable.

So a current ‘Mini’ is as ‘mini’ as a Winnebago is ‘tent’. Why not call it something else?

Tricky question, but it’s definitely related to the ‘celebrity’ thing. Let me tack together a few thoughts. Always assuming I can find a few to do that with.

Back to my little mini of the ’60′s. Falling to pieces. But, if it had ‘Bently Turbo’ stuck on the front somewhere, and I did a bodywork relocation of the whole Bently Turbo in total, it would be a very different animal so far as KUDOS goes. The fact that would have a hard time ripping away from zimmerframe dragsters at the lights is beside the point. It looks like something it isn’t and that (currently, anyway) is all that matters.

Back to Laney. Laney bought Vox. The name anyway. This Vox AD50VT was made in Korea, under the instruction of the r+d dept of Laney UK. Which means that it was made somewhere else, by somebody else, and maybe overseen by somebody who had never seen it.

Laney is not Vox. If they survive another fifty years they might be. They might not.

But this is not a ‘kick Laney’ exercise. Although you may not have guessed. It’s a ‘Why not tell folks what they’re buying, honestly’ exercise. Laney designed a lovely little amp called an LC 30; the subterfuge is pretty obvious even to a trusting old git like me. ‘LC 30 approximately equals an AC 30′. No it doesn’t and never will. If we go no further into it than to appreciate that the Vox AC 30 was hand built from the ground up, and no pcb ever got any nearer to it than the moon, that statement that would flatten almost every amp made in the 30 years or so, not just Laney.

I think that this particular ploy has cost Laney dearly in Kudos. The little LC30 is/was a great little amp in its own way. The company could have trumpeted that fact because it was worth the effort. But they chose to hide behind the fact that it has some circuit parallels with that legend, the ‘Vox AC30′. So it became an also-ran behind the legend, when it should have been sparring at its own weight. And it was very good at that.

Things are different and worse, now. Nondescript manufacturers based possibly in the orient (or somewhere) and staffed largely by robots, buy names; or ‘logos’; call it what you like. The stuff you find inside these ‘Carlsbro’s’ and ‘Vox’s’ and ’Wharfdale’s' etc. etc. bears no resemblance to those companies’ productions as they once were.

The plus side to this is that lower end gear tends to be at least affordable. At a time when a mini cost a bit over £300, the Vox AC 30 was something over £120. And a Fender Strat was a bit over £160. To get hold of either of those cost you a few years on the ‘never-never’ (hire-purchase) so it was a big commitment. At that time you could buy cheaper gear (Bird, Elpico, Watkins,) but you did know what you buying. It had their names on it and they were proud of it.

 

 

 

 

The Little Red Clip light comes on/ the Protect light comes on.

I read a forum the other day where a lot of fellers were scratching their heads about little red lights, on a beefy power amp.

Does the clip led come on when you wind up the volume, without any other indication? (Like green signal present; or orange, signal level ok.) Do get no sound out of it?

It’s only mosfet amp will do this.

Most power amps won’t bother if you run signal through them without a load (speakers etc.). Remove the speaker. Bring up the signal through the amp. The led’s function as normal?

You have open gate mosfets, probably all of them. This means that the control gates in the output devices (mosfets) have blown open and aren’t controlling anything. This sort of fault can happen progressively. Because mosfets will power-share, if one goes open, the others will take over and share out its load between them. This means that they are all working a bit harder, getting a bit hotter, so the weakest will blow open. This is obviously a progressive thing, which is why you get to the completely open output stage, eventually. Anyway…….

Answer? Replace the mosfets. Probably all of them. This is not really a DIY job.

This fault will not happen in a bipolar amp. They short and take out power supplies etc.

If the protect light comes on at switch on, it often means that one half of the output stage has fried. It’s a rebuild, often.

Tea time.

Fender Bassman 135

This was a silverface Fender Bassman 135. It was bound to be really, because they were only made in silverface design, the 50 and 100 being earlier versions that made the transition from blackface to silverface.

This was a ‘come back’ job. They don’t come along very often, but just once in a while……..

Well, the whole story goes like this. It came in, in the first place having lost power and the output being distorted. The output valves were from way back, and on the scope, the signal was very bottom-heavy. One half of the output stage wasn’t pulling it’s weight, one output valve having lost the internal contact to its screen grid. In which case that one did very little.

A new set of output valves went part of the way, but it turned out that the phase splitter was giving an unbalanced output. (They sometimes call it a ‘driver’ these days, but it isn’t. It splits (inverts) the phase to the output valves so that they work in opposing pairs.) There are explanations on this site which go into more detail (that’s in between the silly asides). The phase splitter has to supply the same rms value signal to one half of the output stage as it does to the other. Otherwise, any biasing-balancing you might do will be a waste of time. So there was a repair to made on the phase splitter.

All this was sorted out and the biasing set up, and the amp ran on test for an hour or two without problem. It went out.

It came back. The guys had got into the studio and…….it didn’t work. At all. Bugger. The lights came on. the heaters came on, but no sound.

Now we get to the point, and it actually applies to quite a few different Fender amps, from many eras. The output jack to the speaker is right next to the extension speaker socket. The extension speaker socket is switched, and the signal to the main output is sent through the switching in the extension socket. Bad/dirty contacts there and you get nothing out to the main speaker jack. That was what it turned out to be. Answer? Turn the amp off. Spray contact cleaner into the ext jack, whack a jack plug in and out a lot. Remove jack plug. Walla! Done. Job’s a good ‘un.

Any more problems might indicate a jack socket change, but this was a happy little Fender Bassman 135. Intermittent faults can be a real dog, but getting excited doesn’t usually solve much.

The tea pot calleth.

 

Bugera BC30-212

This the first blog on this site for I think about a year. By not writing any blogs I suspect I postponed a sackload of hair loss. Unfortunately I don’t have the sackful I lost over the previous year as a comparison.

Just so that you might not think that it’s all your fault, the reason that this literary triumph has been in suspended animation for this long year (or short year if you happen to be one of those folks misguided enough to read it) it is because of the attentions of various internet factions.

Far be it from me to point the finger of an irate god at those internet vandals who have wonderful stretches of time to waste on buggering up other folk’s miniscule creative efforts. (Clearly it’s not ‘far be it’ because I already have.) Rather than waste similar amounts of my own time in putting it right, I decided to let it go to the dogs (‘Gods’ for those of a theistic persuasion). Time is one of those strange things that you can waste in truckloads if you have plenty. I suppose that goes for just about anything.

Now I’ve got that steam pressure blown out of my ears (or wherever), onwards and upwards to the Bugera BC30-212 combo. Maybe not ‘upwards’.

Make sure, if you do insist on poking around, to UNPLUG, LEAVE IT A WHILE, AND THEN ASK NICELY WHETHER OR NOT IT’S GOING TO ELECTROCUTE YOU. These things have never told me, before running a few hundred volts up my arm, but you might catch it on a good day.

Just to get a handle on where we are, this is looking into the chassis of the amp from the back, towards the rear of the front panel.  The orange cable goes to a spade connector which carries around 350 volts. You can’t see it too well, but the pcb is badly burned where the connector is soldered to the front pcb.

 

The the fault description was that it fizzed and smelled. The customer switched it off (wise chap), but then he tried it again, and although everything seemed to light up, and there were no further fizzes etc, it just didn’t work.

Here’s another confusing picture. The mirror-like plate facing, is a bit of screening foil stuck to the top of the cabinet. The amp fits into the slot below, and the circular burn mark in the lower left hand corner, was directly over the burned contact we looked at in the last pic. So it had obviously produced some smoke and heat.

 

I have to admit, I don’t like Behringer things. And this a Behringer product, I understand. Behringer is German, this is probably designed in Africa, built in China from parts sourced on Mars. But how would I know? I do know there is plenty of ‘Behringer knocking’ goes on, some deserved and some not quite, but their gear does fill a useful place in the market, as they make something that looks good, and functions often pretty well, and makes available these things to the lesser financially affluent. Such as me. It’s just that I don’t like to move them about much, in case bits fall off. Sorry, that’s just bitchy.

My real problem with Behringer, and a few others of their ilk is that they are just far too precious (for something that is really paste). Try getting hold of some information in the form of a schematic. After a lot of looking over a long time, I’ve never found one. When it comes down to it, there are not many original designs around. The stuff that Leo Fender was designing in 1945, is little different to the same sort of thing that Marshall (for instance) is doing this week. Except in 1945 they were built with a different ethos. They wanted the amps to keep working, and, 70 years later, many still are. Bugera in 2080? Can’t see it, myself.

Back to the plot, if there was one and if I can remember what it was.

Valves and pcb’s don’t generally go very well together. There are many reasons for this, but one in particular is relevant here. A cheap pcb often will not have a very high breakdown voltage. This means that high voltage can arc or track through the insulation; and this means that the insulator ionises and becomes a conductor, shorting across the copper tracks with high voltage differences. This is much more likely to happen between copper tracks and pads etc., that are close together.

The burned contact in the pic was partly down to this arcing/tracking, and partly that the joint to the pcb had been poorly manufactured, had heated the pcb and helped to get it to arc across.

It’s simple enough to correct the burned connector. Scrape the laquer from the track, run solder along it, and solder a link to the spade connector. Unfortunately, that won’t cure a tracking fault. Once the pcb has ionised, there’s not much you can do about it.

But here’s a couple of possibilities, neither of which would will work in this situation, as the tracking is extensive in a completely different part of the circuit.

One possibility is to scrape away at the burned section of the pcb (sometimes you need to scrape a hole through the pcb). Sometimes this will work, but often not. Usually worth a shot, though. The other way will work if you have room to do it. Cut the tracks so that you isolate the complete section of burned pcb. In other words, the copper track remains but is cut either side of the burned section of pcb. Then you scrape away the laquer down to the copper on the copper tracks either side, flow solder onto it, and solder an insulated link (piece of wire) to those, thereby isolating the shorted bit of pcb.

Some years ago C Audio had some desperate problems with their RA3000 amps. Great, high quality, rackmount, high power (3000 watts rms) amps, that had a thing about fog machines. After some time, the fog that was taken in by the amp’s fan rotted the laquer of the pcb and caused tracking all over the place. The ‘standard fix’ was to cut a load of tracks and link them. Those links went from the front to back of the amp and were about a foot long!

The traditional way to build a valve amp is with either point-to-point wiring, tagstrip or turretboard. The times those things track across or burn are almost never.

Tea time!