Craig Sawyers

I've got a forward looking one that is not in the car at the moment - the micro-SD card died. New one on the way. But if I was doing this again, I would have the variety that looks both forward and backward so you can record rear end collisions, or car park damage.

Easy thing to check with a thermocouple for anyone with a carbon or kgsshv. The caps in the KG-T2 probably get pretty toasty, but that animal drags ~200W out of the mains, the transformers run hot, and there are two massive heatsinks along each side of the case that also get hot. So although I have not measured the temp of the reservoir caps I suspect that they get pretty hot through association with their surroundings. But noone is gong to leave the T2 on for much longer than you are listening; I let mine warm up for an hour (two max).

OK - I'll bite - what is KR, ( M ?

This was too good to be true. So famous that Wikipedia has an entry, with first sentence (wait for it) "Vera Coking was a retired homeowner in Atlantic City, New Jersey whose home was the focus of a prominent eminent domain case involving Donald Trump." https://en.wikipedia.org/wiki/Vera_Coking

All down to Arrhenius for semiconductors. And electrolytic capacitor life about halving for every 10C temperature increase. Not counting infant mortality. And thermal shock every time it is turned on. So in this context, what do you mean by MTBF?

I was wondering that too - I don't immediately recognize the glass envelope.

Well bugger me - I'm British through and through back as far as I've looked (late 1600's) and I knew absolutely none of that. Other than that there is a City of London, I had no idea of the inner machinery.

Happy birthday!

The other thing to work out is which end of the primary winding is next to the secondaries. You really want the hot or live input to be next to the core, and the neutral or low input next to the secondary. It will of course be perfectly OK the other way round, but makes-borne noise coupling via the interwinding capacitance much easier. As far as I know there is no straightforward way of figuring that out.

Somewhere I have a photo of some poor sod's old man after he peed against an electric fence. Imagine you took a blow torch to a sausage, for several minutes.

Yes - Dalbani were the outfit that supplied me with junk 2sc3675's. When I put one or two spares on the curvetracer they broke down at 400V or thereabouts instead of 900V minimum. Avoid Dalbani like the plague.

$6+ seems to be what 2sa1968 are going for now. And there is no guarantee that even they are genuine. A 20c part is almost certainly fake IMHO. I'd say you have some major problems.

^Every time - every damned time - you reduce me to gales of laughter

That indeed is a good point given that the main semiconductors are long obsolete. My T2 went together during the first builds with fake 3675's and actually produced sparks. Killed just about every bit of silicon as collateral damage.

Current world pi memory record 70,300 digits http://www.pi-world-ranking-list.com/index.php?page=lists&category=pi took more than 17 hours to recite it. I actually saw a guy back in 1976 who only had only 10,000 digits, but had it in random access - given any three or four digits at random from the number he could continue from that point immediately. Same event (at CERN) that Wim Klein extracted the 73rd root of a 500 digit number in a little under 3 minutes. Klein's party trick was going out for a beer, and walking though the car park would memorize all the number plates and make/colour of each car. People in the bar would test him - he never got it wrong. He was employed by CERN to debug computer code - he was capable of doing a mental dry run to find tricky errors. Good heaven - I found a photo of that event on the web. I'm five rows from the front, 3rd from the right, checked shirt. Klein is standing, and the guy sat next to the projector is the pi man - totally forget his name. http://www.symmetrymagazine.org/article/december-2012/%E2%80%98human-calculator%E2%80%99-wim-klein-advanced-physics-inspired-others

Are both channels the same in this regard? If so, have you checked that the LED's are the right way round, and the 100V zener is the correct way round?

That is where your active diff probe comes in handy. But interestingly the really old generation Tek probes, I guess because of their physical size, can handle much higher voltages. http://www.reprise.com/host/tektronix/reference/voltage_probes.asp Although CMRR would not be as good as the current product, using two P6000's say, inverting one channel on the scope and adding might skin that cat. There are two NOS P6007 on eBay at the moment for about $70 each BIN/ONO, x100 and handles 1.5kV AC and 2.4kV DC.

^That, old son is good natured

OK - decent scope, but be careful what and where you probe. My tendency would be not to probe with the T2 turned on - one slip with the ground lead, probe tip or your finger could spoil your day big time. I would turn the T2 off, attache probe connections and turn on again. But bear in mind that any complex feedback amplifier can oscillate - IIRC there are the odd single figure pF capacitors in there to stabilise the amp. Also probe impedance can modify the effect - either stopping the oscillation, making it worse, or changing the frequency.

Now you're hitting my buttons. A Quad-like array of Neoliths.......

I'm speechless. Who would? Why? Back on planet earth, ML recently introduced the Neolith; the design brief was anything goes with the only requirement that it fits though a standard domestic door. At around $100k you could buy 50 of them for the solid gold microsystem above.

Yup - that'll do it. Nice probe. If you can cope with x100 and x1000 attenuation.

What scope, what probes? Highly specified Tektronix probes only handle 300V for a x1 and 450V for a x10 non-destructively. Generic probes can be much less, or poorly specified.

This is the reason that Krell went over to some sort of dynamic biassing scheme, because running flat out class A was just not reliable. I had a late model KSA100 that demonstrated that perfectly. Typical Krell battleship construction, with superb engineering, and two fan cooled heatsink chimneys. Power transistors were rebranded as KrellA and KrellAA. It blew up three times in my ownership - same symptom each time, power transistors going into second breakdown failure accompanied by lots of smoke. Lat time it happened was after I had sold it on eBay for quite a lot of money. The buyer was actually on his way to collect from about 150 miles away - and I thought I'd turn it on so he could listen to it. Major league failure with plumes of smoke; phoned him in the car, apologised profusely and he went back home. This time it had taken out the drivers too, and the associated driver load resistors had ignited and burned part way through the board. Replaced the sand, using generic high power transistors and NOS obsolete drivers. Dremelled out the char and coated with conformal coating before replacing the load resistors. Worked perfectly, and the guy honoured the sale, paid the money after auditioning and off he went leaving positive feedback. I've also seen the same generation of KSA50 ignite too. But it is all down to component stresses - high power class A puts a combination of high voltage and high current through the power devices all the time. Smoothing caps and power transformers likewise need to be carefully thought about, since they are running flat out all the time too. But non-linear distortions, including induction distortion are much lower than class B or AB, which is why high end users like it.

I just love you guys - I'm still laughing five minutes in