Craig Sawyers

Last time in the UK was 5 years ago at Covent Garden. Tickets sold out in five minutes flat. Watched it televised - Terfel as Wotan. Actually he only survived Das Rheingold and Die Walkure and then keeled over. So John Tomlinson stepped in to the breach without rehearsal for Siegfried and Gotterdamerung - but Wotan plays a much smaller role in those operas. 17 hours of opera, and *everybody* dies apart from the Rheinmaidens. I love the damned thing - murder, incest, corruption, lust - every deadly sin on a grand scale bolted together into a single epic. Based on the same Anglo-Saxon and Germanic legends as Lord of the Rings - but with adult content, and no Samwise Gamgee (thank heavens). Oh and and every year at Beyreuth. But you have to apply for tickets each and every year until your name comes up. Miss a single year - back to the start of the queue. Currently 7 years wait.

Sorry 'bout the poor Bach 'reks. We had a much more successful classical outing - Die Meistersinger with Bryn Terfel singing Hans Sachs. Absolutely awesome production, and Terfel was stunning. One of Wagner's easier to get to grips with operas - ie there are real tunes. Booked that one in January! Rather than Tristan und Isolde which is hours of unresolved musical tension (on purpose, to match the continual tension in the stage situation) leading up to a final marvellous aria called the Leibes Tod (love-death). T und I is a tough opera to watch and get under the musical skin of. But whichever Wagner you see you are in for at least 4 1/2 hours. Or for the full Ring cycle 17 hours. Awesome. In two weeks we're up for the second Ring opera, Die Walkure, at Longborough. Pretty much an all day affair.

I have to keep looking at the different definition of gallon on each side of the pond. 1US gallon in 3.78 litres and 1UK gallon is 4.55 litres. On the freeway at 80mph in cruise I average 18 mp(UK)g, which is 22 mp(US)g. So less for sure than your 'vette - but it is a much older engine design. Also, mine is the so-called HE engine (for "high efficiency":)), which had a domed head and a monster 12.5 compression ratio. The older flat head low compression engine gave 14mp(UK)g on a good day. That sounds about right. Early Lotus cars were the same - they had a straight 6 with three SU carbs. But to fit the engine in the squat profile the engine is canted over with the carbs *underneath*. Also the Triumph TR7. Owners of all these cars are constantly tweaking the damned things. Sounds like a plan. Try shaving 1/8" off one end and see how it goes.

I was lucky - I snagged a 13" x 2-3/4" square piece of true LV. Drove a fair distance to pick it up. Have used a strip off one side to make fences out of for my hand rebate planes (3 old Record ones, and a skew mouth Lie Nielsen). It is great because of its self-lubricating properties and its extreme harness. There is the most astonishing perfume when freshly cutting the wood from the exposed oils. Lignum Vitae means wood of life, because it was believed to have medicinal properties. I cut a 4" chunk, which is the one that Kevin now has in the photos. I use a bandsaw to cut the stuff, not a table saw. There is less waste using a bandsaw too (thinner kerf), but you have to be careful to minimise wander, and cut slowly and steadily. Vera Wood is interesting - also called Maracaibo lignum vitae (Bulnesia sarmienti), and is a great wood. My wood supplier says of Vera Wood (which he calls Palo Santo wood): "Although this wood has been used for generations for the same purposes as the genuine lignum vitaes (timber from the genus guiaicum) it has become a more important choice recently because of the listing of the Guaiacum lignum vitaes on Cites appendix II. Genuine lignum vitae is currently only possible for import with Cites export and import documentation. In practice this means there is not a lot coming through."

Yeah - service repairs are always horrendous. I ended up retiring the car in around '95 after it let me down with coolant leaks far too often, but couldn't bring myself to dispose of it. So I shoved it in the garage, and when I found some time (oh - around 2 years work in evenings and weekends) I rebuilt at nut and bolt level. Horrendously expensive job. Fortunately my local Jag garage (TWR Oxford) lent me all the specialist tools necessary. So there is absolutely no way it is going to let me down (knock on wood). Plus it only gets sparingly used, and only in the Summer to keep the rust worms at bay. Throttle linkages is a doddle. You undo the locknuts on the ends of each linkage. One is a left hand thread and the other a right hand one. There is a knurled bit on each link rod to grasp between your fingers - you just turn each link rod until there is a little slack, and the throttle pedastle takes up that slack on both links at the same time. Tighten the locknuts - job done. Certainly nothing like as difficult as the pre-injection, very early 4-carb V12 engine was to adjust. Two SU carbs each side, with each one feeding three cylinders. Balancing that up really was the stuff of madness and dragons. Corvette looks like a real champ Kevin - nice beast. Like my Jag it must drink fuel like crazy

Lignum Vitae

I suspect that it is more likely to be due to interwinding capacitance in the power transformers than the alumina insulators. That is why two-pin appliances have to be double insulated to keep chassis parts away from human contact. OK, I'll bite - what vintage of corvette do you have? I rebuilt and restored a 30 year old Jaguar V12 saloon (sedan) a few years back, end to end. There are a LOT of bits in a 5.3L V12 and GM400 gearbox. For project cost imagine a pile of dollars and a shovel. For anyone remotely interested, here are some pics of the finished beast http://www.tech-enterprise.com/tekstuff/DSCN0194.JPG http://www.tech-enterprise.com/tekstuff/DSCN0195.JPG http://www.tech-enterprise.com/tekstuff/DSCN0196.JPG http://www.tech-enterprise.com/tekstuff/DSCN0197.JPG http://www.tech-enterprise.com/tekstuff/DSCN0198.JPG

Daughter's graduation ceremony yesterday, which was very good. Stupidly hot (for the UK) at 32C (90F), made much worse because we don't do room airconditioning to any great extent here, so the large and sealed marquee was a solar powered oven. The car was a blissful relief by comparison. Today off to see Die Meistersingers with Bryn Terfel in Birminham. Typical Wagner epic-length opera - starts at 4pm and ends at 10pm with two intervals.

Thanks for the heads up - I'll watch that one when I build mine up. Great to hear that the beast lives, and sounds great! Can hardly wait. Mrs S picked up the credit card bill today, which had lots of money to Mouser, Farnell, Dalbani etc on it. It sure was an interesting conversation (not)

Inu - tell us more, more more!

Good it got to you in good shape, Kevin - massively looking forward to what comes out

Lifetime (MTTF) data on specific transistors is very difficult to pin down. Generically for silicon at a junction temperature of 150C it seems to be around 10^6 hours, or 100 *years*, assuming it is a chemical activation process - defects, contamination etc. People do elevated temperature testing to reduce MTTF to a few thousand hours and then extrapolate. There is an arcane paper here http://rel.intersil.com/docs/rel/calculation_of_semiconductor_failure_rates.pdf that sets out some detail.

I was lucky enough to see the 1982 Footlights Review while at Southampton University. Imagine Steven Fry, Hugh Laurie, Emma Thompson and Tony Slattery together on stage.......

Really glad they sound great! Fine speakers. Regarding bases, Quad restorers tend to collect a rouges gallery of bits from speakers that were not economically repairable and are scrapped for spares. I would imagine that Wayne would be able to dig out a couple of suitable bases. If not let me know - I'm sure One Thing in the UK will have precisely what you want - and they ship internationally regularly.

I kind of reckoned that I'd defaulted to lecture mode quite enough for one day . I do have a habit of banging one once I get going. But you're right - with the plastic package you get one layer of grease, and with the alumina you get two. So add another tenth or so per layer.

It doesn't go anywhere as such. The only thing that matters is the temperature of the silicon. That is usually taken to be 150C or thereabout. So if you are bolted onto an infinite heatsink, the thing that determines the temperature of the silicon is the package thermal resistance. So, if the TO220 metal package dissipates 178W on an infinite heatsink with 0.7C/W, the silicon temperature rise is 178 x 0.7 = 125C, plus the heatsink ambient of 25C = 150C. Similarly for the plastic package, the silicon temperature rise is 59 x 2.1 = 124C - the same number (within the accuracy of the numbers). If the heatsink is hotter - because in the T2 there are lots of devices attached to the same sink - you have to derate things further. The total calculation involves adding together the thermal resistances, in this case package + heatsink-air, so 2.1 + 0.3 (guesstimated) = 2.4C/W. Assume heatsink temperature is 35C. So maximum device dissipation is (150 - 35)/2.4 = 48W. For the metal device, we have to use a heatsink insulator - which is say 2C/W. So we need to add up package + insulator + heatsink-air, or 0.7 + 2 + 0.3 = 3C/W, giving a maximum dissipation of (150 - 35)/3 = 38W. Of course, you would not operate a transistor die at 150C - you'd derate it to <100C for long term reliability. Which would mean max device dissipations of ~27W and ~22W respectively. But anyway, the upshot is that the plastic packaged device gives better thermal performance. The only way to equalise them is to reduce the thermal resistance of the heatsink insulator for the metal package to ~1.4C/W - but we're stuck with alumina which is 2C/W for a TO220. Running some quick numbers the T2 devices run around 5W quiescent and perhaps 10W maximum - so safely inside the dissipation limit with an alumina insulator.

The trick with getting good TO220 thermal contact is to apply the right fastening torque, particularly with the elastomer insulators (but also with hard insulators like mica - or alumina). The spec depends on manufacturer, 0.8 - 1.1Nm (7 - 10in/lb) in one case and 0.49 - 0.686Nm for Sanken. Beyond that the tab starts to deform enough to lift the pressure off the body - the package sort of pivots upwards. I though that the plastic TO220 could take more torque - but the specs do not indicate that - the same as for the metal tabbed version. I bought a torque screwdriver a few years ago for precisely this purpose - and the correct torque is surprisingly slight. When hand tightening, I've found that the tendency is to massively overtighten. As you increase torque, the thermal resistance falls to a minimum, and then increases again as you tighten more. The way around that is to use a hole-less insulator, and one of those spring clips that bear in the middle of the transistor body. Keeps voltage isolation high, and applies much more pressure since there is no risk of pivoting. The problem is that you need a heatsink extrusion with a feature into which the clips engage.

But that is down to the total thermal resistance. Junction to case is 0.7C/W for TO220 and 2.1C/W for the plastic case - a ratio of 1:3, which is the same ratio as the maximum power dissipation (ie 178/59). But for the TO220 you need the ceramic insulator - which is 2C/W. So the total thermal resistance for the TO220 plus alumina insulator is 2.7C/W as compared with 2.1C/W for the plastic. So the plastic should actually dissipate more power than the TO220 in the T2. It is also stiffer than the metal tabbed TO220 (which is a nightmare package to bolt down and keep it in contact with the heatsink), so should stay in contact over its whole area with the heastsink.

For anyone who hasn't been watching Glastonbuy, do a You Tube search for Matt Smith Glastonbury. To cap one evening off, he did a 5 minute set with Orbital of the Dr Who theme tune. Enough whizz bang special effects to blow your mind - and I speak as someone who has seen Jarre twice. Treat yourself and watch.

Well, apart from the 2SC3381 both boards are now completely stuffed. I'm getting a little wary of pushing those into the holes though. Although KG opened them out a tad, just enough to leave some plating on the inside of the holes they are still reportedly a very tight fit. The holes seem to be a tad under 0.6mm - a #74 perhaps (0.57mm). I need to stock up on carbide circuit board drill bits anyway, so I have put a couple of 0.65mm on the list. Across the corners of the square pins is 0.63mm (2SK389's actually measure 0.59mm) - so an 0.65mm should work nicely. The downside is that 0.65mm will definitely take out the hole plating - so I'll have to carefully solder both bottom and top side pads. I'll report back once I have the drill bits and the 2SC3381.

Wow - well spotted! It is indeed a TDL transmission line speaker. They are one of the few companies to tame the somewhat wooly bottom end of a TL speaker. Still around History

You have no idea what relief that comment means! The number of things I have that have made it to circuit layout, board manufacture, stuffing then stall when it comes to the boxwork. Apart from finishing stuffing the KGT2 (and thank heavens the Kevin has done the casework design and is supplying to us builders), I too have be de-shelving a dynahi this weekend with the determination to finish the darned thing off. And that is just the start.

Or www.rswww.com at 99p each, their part number 671-5199 - where I got them from. Their website is down at the moment - they often do site maintenance at the weekend.

ELECTRONIC COMPONENTS, SEMICONDUCTORS, PARTS, TRANSISTORS, INVERTERS, TRANSFORMERS | DALBANI

Just took the car for an MOT test (in the UK every car over 3 years old gets a roadworthiness test; takes an hour). Horrendous traffic so I arrived 10 minutes late. Guy refused to do it. I was not a happy bunny. Been going there 18 years - so much for loyalty. Last time too - time to go somewhere else I think.