Craig Sawyers

Sounds like a pretty good day to me

Depends on what your budget is. I've recently gone to using a TentLabs CD player, which sounds completely stunning - a real giant killer. It is nominally a DIY player (!) but is actually supplied as completed electronics modules, requiring screwing together into the casework and wiring up. Link is here Tentlabs DIY CD player . I actually got mine in a known not-working condition as payment in lieu for some business advice. Turned out to be a weakness in a power supply regulator, and current production now incorporates my fix. In any case, Tent repaired the unit free of charge without quibble (5 year warranty). If you don't feel comfortable building the unit, you can pay more and take delivery of a built one. The caveat is that if your budget is the sort of price for a used CDP-2, the Tent is going to be a very expensive option.

Been there, done that, with a Georgian front (ca 1760)/Victorian extension (ca 1870) around 20 years ago. It was a helluva job, but worthwhile. Fortunately we did not have a foundation problem. But the wall could be bowing for several reasons - it either may not be structurally well connected to the rest of the building, or the foundation might be poor. The first is relatively cheap, because the wall can be pinned back onto the rest of the structure. The foundation is much more of a biggy, and it depends on why it is sagging. If the ground is poor (boggy etc), there is not much you can do. but if it is just that the building was not properly founded it can be underpinned, but think major expense. Here in the UK you see lots of old properties in which bowing walls have been corrected by bolting them back together. Basically a spreader plate on opposite walls, and a very long metal rod with threaded ends that passes through the space under the floorboards at first floor level. Repeat as necessary along the wall. Also used in the US - there is a thread about it here a bulging brick wall & star-shaped bolts! - Old House Forum - GardenWeb

Think of it as a completely floating (ie not necessarily ground referenced) zenerless ideal voltage source. So very low noise, because high voltage zeners (in fact anything >6.2V) operates in avalanche mode, not pure zener, and is an excellent wide-band noise generator. Basic idea shown in the T2 schematic, which can be found with a bit of searching on the T2 thread. 6.2V mentioned above actually has a relevance to zener calibration standard voltage sources. Because this voltage is the transition between zener action and avalanche, and they have opposite temp coeffs. So 6.2-ish volts is exceptionally temperature insensitive over a narrow range. So such sources have zeners which are designed with the insensitivity at room temperature (20C), or at an elevated oven temperature (30C or so). All of which is completely irrelevant to any high voltage design useful for electrostatic phones.

Bitter sweet - I recognise that feeling. Bloody well done!

Jeez. Looks dreadful. Glad you and yours are safe.

That, sir, has left me totally helpless with laughter!

Looks great Kevin - it is a bugger to work being so tough. But real Lignum Vitae has a wonderful perfume, doesn't it? Really looking forward to seeing the final thing. You definitely need pilot holes for the screws though, or drill and tap - just as you would for metal. As you know I tried 1/4UNC and M6 with perfect results.

That is my stock phrase to team members when things aren't happening quick enough: "C'mon guys - this isn't rocket science. Wait a minuite....". This instrument is a real pushing-the-envelope thing. There are two X-ray imaging spectrometers (to look at the chemical makeup of Mercury's crust) mounted on a 1 meter long optical bench. There is also an electronics box with a multi-output switched mode supply and a data processing unit on a 14-layer circuit board. Total weight is 8kg (17lbs). It has to be seriously radiation hard too. In order to do the science, the sun has to be spitting out x-rays, which only happen when the sun is in an active phase - when it also throws out massive amounts of radiation. One consequence is that FPGA chips, which are normally around $10, cost $19,000 each in the space qualified grade necessary.

The single large ground pin is specced at #16

Deliver the units to on time and to cost target. International team of around 80 involved and a budget of Euro14m. Stuctural and Thermal model delivered on schedule, Electrical Model due for delivery end November, Qualification Model due around Spring 2011, and Flight Model Jan 2012. Overall buck stops with me.

Due to start on Monday in a half-time employed role at Leicester University. I was actually doing the same thing for 2 1/2 years as an external consultant, but they could not cope with even longer as an external bod. So - and heaven knows why on earth I agreed to this - I said I'd take a huge pay cut to continue doing the job as an employee - and (UK) academic salaries suck big time. I'm not really salary-constrained in a major way, and I kind of have a good rapport with the team, and a sense of responsibility to see the thing through - and that swayed the decision. This is as Project Manager for a deep space instrument called MIXS (the Mercury Imaging X-ray Spectrometer) due for launch by ESA in late 2014. NASA have the second only spacecraft (Messenger) visiting Mercury about now; it is not in Mercury orbit yet, but doing fly-bys as it slows down enough to get into orbit. Ours will be the third mission (BepiColumbo), getting into polar orbit around the planet in 2020. All sorts of planetary gymnastics on its 6 year travel to catch up with Mercury - as has been the case with Messenger.

Oof.

The amazing thing is that the active, signal-route part of the circuit, is four tubes and four FETs. Everything else is either current sources or voltage sources. Plus the servo, of course.

Bored and twiddling my thumbs waiting for semiconductors to arrive to fix the zapped T2, I thought I'd try to get a grip on what the actual signal level circuit was doing. I've replaced all the current sources and 740V battery with ideal symbols. I've also left out compensation components, and some of the details of one or two current sources which I think are error handling, to prevent the thing blowing up if a tube goes down badly. I think the result shows the rather neat symmetry of the design, and the clever way in which DC voltage shifts are generated using the FETs and batteries to move the ground referenced input signal to -500V. File is here http://www.tech-enterprise.com/tekstuff/T2deconstruct.pdf

Interesting. I've just measured where my ESL57's are - 56" from the rear wall and a ceiling height of 90" - so a ratio of 0.62! I seem to have iterated to GC's golden ratio just based on moving them around and listening.

George Cardas is one of the audio business good guys. Fixated on golden ratios for sure, but that fixation has led to some exceptional results. His golden trapagon stuff is aimed at distributing the room resonances at the listening position in an acoustically acceptible way. But it seems to be suited to monopole speakers (ie ones in boxes) that are omnidirectional at low frequencies, and excite resonances in all three room dimensions. I'd be interested in learning what his thinking is on placement of dipole speakers (such as electrostatics, or Magneplanar panels) which excite resonances only in one room dimension.

I guess you were lucky you were only dressed as a wolfman - could've been a whole lot worse.

Reminds me of someone I met at a strange party long ago.

I vaguely recall slowing down some of the scenes to see the detail of what happened to the crew. Not pleasant. But you're right, a load of tosh.

Hokay - here's where I've got to. No progress on zapped channel. Waiting semiconductors. But some progress on the one with stuck battery voltage. Symptom was two LED's in one of the current source triples would blow. They would flash very brightly and then blow. One of the 3675's in that triple was open circuit too. So I spent a cheerless hour or two pulling semiconductors. Everything checked out fine - all MOSFET's absolutely fine, all junction transistors likewise fine (apart from that one 3675). Then I spotted it - it was either Q32 or Q33 - I had missed soldering a pin! Boy did I feel a dope - I must have been interrupted half way through soldering and skipped a joint. Anyway, whereas previously both batteries were stuck, but at significantly different voltages and LED's died, they are still stuck, but within a volt of each other at 570V. LED's are all OK (checked with a 9V battery in series with 6k8 resistor) so LED death is cured. Current triples and bottom current source are not turned on, but the battery LED chains are lit. So no anode current in the EL34's. About the only semiconductor I haven't checked are the JFETS in the batteries. If they were phut, that would explain lack of adjustablilty using RV2. Sounds like the next check. All other semis in the batteries are fine - checked in circuit just using diode test on the DVM.

I'd agree. Given Inu's comments on the fact that using old stock Amperex 6DJ8's killing the 2SK216's no matter what he did, I think that that one messes with this design with real caution.

Well, the two K216 left over from the build produce traces identical to those in the Hitachi data sheet - to the extent you could pretty much substitute the curves. My Tek 177 curve tracer won't generate enough voltage to trigger the gate protection zeners. But the drain-source diode seems to be present just using the diode function on the DVM. The thing I don't understand is the 2N3675 in one of the active batteries (the one connected to Q4) has suffered second breakdown - it is essentially short circuit between all three terminals. Q27 and Q28 (2SK316) are dead, as are D21 and D22 (100V zeners). Three dead LED's in the current source triples (D10, 11 and 7). So the sequence of events is a little puzzling, and I cannot think of a mechanism that would lead to dead LED's - other than infant mortality. Everything connected to them in the current sources is A-OK.

That is a dark and worrying though, Justin. I've got a couple of spares (they have the Hitachi logo, but that counts for nothing) that I'll throw at the curvetracer and see what they look like.

I do beg your pardon - you are quite right. I hadn't spotted the thermals that make the connection.