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.