Craig Sawyers

I will say this only once.... The main actor (played Rene), Gorden Kaye (yes - Gorden, because Equity misspelled his name) was darned near killed is a massive storm in 1990 that cut a swathe through the UK and mainland Europe, with over 100 deaths including Germany and France. Kaye ended up with emergency brain surgery (completely successful) after a chunk of wood was propelled through the windscreen of his car and hit his head. He's still got massive scars on his forehead to prove it. The BBC account of the mayhem of that day his here BBC ON THIS DAY | 25 | 1990: Children killed in devastating storm

Ah - the logical opposite of Sgt Pepper, I see....

Struts - I know you've answered your own questions, but I thought this might be worth elaborating. The chassis components are all anodized, which is a very good electrical insulator. With such high and lethal voltages I was concerned that isolated chassis components could be a significant hazard. The rear of the mains chassis plug is a case in point. I drew a pencil line around the ouline and then carefully used a dremel with grinding attachment to remove the anodizing behind where the plate mounts. I also dremelled the anodizing off areas when the chassis parts bolt together - the front and back plates where they mount to the heatsinks and top and bottom, the top and bottom where they mount to the heatsinks and front and back plates etc. So now all chassis components are decently electrically bonded. The ground wires in the PSU and amp were fixed with butch star washers to the spare holes in the heatsinks in accordance with safety standards. I might blow the bugger up electrically (and have done) but once it is working and cased up it will be safe

Well in my case the C3675's in the battery went short circuit. That massively overloaded the bottom K216 which went short. That massively forward biassed the 100V zeners, which glowed briefly before blowing. The chain of failure also took out D6/D7 by massive overcurrent. Which is why I recommend testing your C3675's for DC current gain (ie *not* small signal slope gain) at 5mA, should be 70-ish or more for good 'uns. 20V is quite enough to test at, and assume that the gain increases by around 10% by 740V (because of the slope in the collector characteristics).

I agree. Dead 100V zeners seems to mean dead K216's. Been there, got the badge (root cause for me, crap C3675's). Don't beat yourself up too much about the wiring error - the good news is that one channel survived the trauma. This circuit seems to be a fascinating mix as tough as old boots, and also kind of frail at the same time. Incidentally, got 115 C3675's coming from three different sources now. If all are good, that is a result - plenty for other projects. But three sources hedges my bets - all three lots are unlikely to be simultaneously flakey.

Ah. Maybe not. Test D10 and D11. If they are kaput, check the 100V zeners and the K216's on that side.

Gate-drain short in Q22? One or all of the 2SA1486's the wrong way round? Wrong values for R33 and R34?

That would leave you without a leg to stand on

What are the voltages at each end of the batteries with respect to ground?

Having just found a wiring error in my Tek 577 curve tracer (which was there since the instrument was built - orange and brown wires were transposed at one point. So Tek could not possibly have calibrated the thing), I can now at last give much more definitive measurements for my transistors. The good 2SC3675 measure a DC beta of between 74 and 90 at 750V and 5mA. Which is why the battery should work with good parts. This matches quite well with KG's base current measurement of 50uA on his prototype battery. The duff 2SC3675 measure a DC beta of between 9 and 11, but you cannot get close to 750V. The curves turn upwards on a fast power law over 550V. I have no idea what crap piece of random silicon is in the packages, but the correct one it isn't. Which is why they die, catestrophically in the T2, with serious collateral damage. The 2SC4686A measure between 30 and 34 at 750V and 5mA, and are probably too low to work properly in the T2 batteries without some mods. According to the spec sheet these transistors can have a beta of up to 60 at 3mA and 5V, but none of my batch do this (and neither did Inu's).

Way to go! Crutches will come easy with a bit of practice, don't worry. Broke my foot around 10 years ago while cross country running, and was given crutches. I was working in London at the time. Big advantage on a crowded commuter train was that I got to use the disabled seat! But using the underground (tube) was a bit of a hairy experience - I was willing everyone to keep clear of my foot - I would not have been accountable for my actions if anyone had stood on it.

Holy crap. Is there a dog somewhere in that pincushion?

Mine in more into rodents. Payed off big time when she started chewing up rats - turned out there was a nest under one of our sheds. Cat would come in strutting her stuff with a scratched up face (rats really put up a fight) having eaten most of each rat.

Both of those stunts almost qualify for the doggy equivalent of a Darwin award! Stinking and quill-skewered.

Nope - the duff ones came from Dalbani. As did the good ones, but the orders were separated by some months.

Had a winter weather incident yesterday. Blizzard like snow storm that dumped 6" in an hour. Got caught in it in the car. Following a taxi along a quiet country road, leaving 50 yards space and driving in third gear (out of six) at 20mph. Out of the white out, a delivery van had stopped on a downhill (he was lost. What a bonehead thing to do - stop in those conditions on a downgrade), the taxi managed to slither out of the way and was slowly edging past the taxi. I went 2nd, 1st gear with the traction control firing off to keep the car going straight. Then I had to brake - antilocks fired off. With 20 yards to go I said to the wife "I'm going to hit him - nothing more I can do". Turned out to be a minor bump - as soon as I contacted him his car just slithered away. Minor damage to his and my bumpers. Could have been much worse.

Ah - OK. I nailed 41 (all the stock) 2SC3675 from a UK vendor at a very good 85p each. They will either all be good, or a waste of money. Let's see if I can get them before Christmas, so I can resurrect the T2 as a personal pressie. None of them are going into the beast until they have been screened for hFE.

Darn. Wish I'd spotted that opportunity - I'd definintely have joined in.

Justin has taken most (or all) of the parts off his site, and only lists finished products. That does not mean that he does not have them, and that they are available for purchase if asked. Either PM him, or contact him via his site. I've bought several DACTs off him after he took them off his site.

Holy shit. I can't get my head around what you must be going through right now. Just hang on in there - you'll turn the corner pretty soon.

And just to add to eveyone's 2SC3675 paranoia, Sanyo are disconintuing the part: SANYO Transistor: 2SC3675 Only 1200 left in Sanyo's inventory. After that - nothing. Anyone in the US up for a group buy of 200 or more (200 is the MOQ) at 86c each? You could certainly count me in for a T2's worth of them (34) plus a bunch of spares.

Bloody hell. Your and my experience with this should sound warning klaxons to all T2 builders - measure any 2SC3675 that you are planning on using!

The 2SC3675 problem is solved. I hauled my Tek 577 curve tracer out with the aim of measuring the hFE of my batch of 2SC4686A. The answer was 25 +/-10%. So I thought I'd try out a 2SC3675 just for comparison. The one I connected up gave the answer ... 10. Say what? So I grabbed another and this was was 70. Another was 10. Then I spotted that there were two batches that looked quite different. One lot has an hFE of 10, the other was in the range 50 to 70. A picture of the two types is here http://www.tech-enterprise.com/tekstuff/2SC3675.jpg . If you zoom in you will see the markings on the packages. The one on the left gives the correct high value hFE, and the one on the left has a puny hFE of 10. All remaining ten samples of the right hand one have a gain of 10. The remaining four of the left hand one have gains of 50 to 70. Of course I have a random selection stuffed into my T2. And the ones that have failed in the batteries are (surprise surprise) the low gain ones. In forty years of designing and building electronics, this is a first for me. The right hand ones in the picture are either a faulty batch, or counterfeit. The duff ones are marked iSC, and may come from this outfit isc,inchange Semiconductor Company Limited Welcome You , and clearly Chinese crap. I'm going to order another batch of these sods, and check every last one before I replace the defective ones in my T2 lock stock and barrel.

Yeah - I can see that snow in Texas is a bit of a rare novelty. But in the UK we get snow on a pretty regular basis. Hell, Cairngorm in Scotland is a ski resort! Now sure, Scotland gets a lot more snow than here in the South (even though only a very few hundred miles separate us), but even there they have ground majestically to a halt - people stranded in their cars for ten hours on the motorways, quite a few fatal car accidents and so forth. This all happened 12 months ago - and their excuse was that it was freak weather which was not forecast. This year all this was predicted from climate modelling a week in advance. And yet again we have not got our act together. In just-OK-is-good-enough Britain.

Everywhere on the planet copes with snow better than the UK. With snow forecast for today in our area, we set off early to pick up the Christmas Tree (from the Christmas Tree Barn at Christmas Common! Seriously). -4C but no snow to start. There'd been a bit of snow during the night as we drove further. Collect tree and then it started to snow big time. Half an hour to drive there, hour and a half to drive back. With snow forcecast for days, we saw no sign of ploughs or gritting. Airports closed throughout Britain, chaos everywhere on the roads. You know how many time Helsinki airport in Finland has been closed in the last ten years? None. In the UK we get 6" of snow and we close the lot. Pathetic.