Craig Sawyers

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.

Semis just arrived, with the only waited for item being the 2SC3381GR. Luckily judging by Inu's post I've got 2SK246GR and not BL. At least I can stuff every semi not heasink mounted (apart from the '3381s) now.

That got me thinking. Doing some calculations, the LED's are all operating at reasonably low currents - either 1mA or around 0.5mA. So they will only light dimly, and from the datasheet develop 1.8V. I'd start looking around D24, Q30 and Q31. These are current sources for Q4, Q5 and provide the current through the batteries. This current should be 1.8 - Vbe = 1.2V across a 240 ohm emitter resistor - or 5mA. In addition if something is screwy with the circuit around D1, the biassing of Q4 and Q5 will be up the chute. One or both of those could well put the battery into an inappropriate regime - if it is expecting 5mA and is getting significantly less for example (I haven't figured the circuit for the battery yet). Er good luck - I'll be in the same place as you in around a month's time.

Looks awesome! Turning on power for the first time is a really sweaty palm moment. Always. The only insurance is to check, check - have a cup of coffee and go for a walk then check again.

Stick with it - it grows on you as you get to know the characters. The musical numbers are not quite up to Family Guy standard (who can forget the FCC number), but pretty good nontheless.

Mongrels. Late night BBC adult puppet show about a group of animals (fox, pigeon, dog, cat etc). Voiced by a selection of comedians - hilarious. Currently at episode 3.

Luther = superb. Shaky start while it found its feet - but excellent later in the series.

Finished the power umbilicals today (getting everything prepped for the arrival of casework in due course). Forgot how fiddly it was to wire up Amphenol mil spec connectors. I guess it took an hour or two to cut the wires precisely to length, twist the heater wires (to reduce hum radiation), pull though mesh sleeve and adhesive lined heatshrink the ends. Then cutting up neoprene sleeving to the correct length (around half an inch). All told maybe 4-6 hours for the pair. After soldering one end I did a pin to pin check to eliminate wiring errors (one found and corrected), and a leakage check to ensure that there were no faults in the ubmilical or the connector. Used an AVO mega-ohm meter, which has a switchable voltage up to 1kV and measures up to 10Tera-ohms (10^13 ohms). Well the leakage of my test setup was 10^11 ohms, so all tests were relative to that (to get much further the whole set up has to be on a teflon sheet). Every pin was checked to every pin, and it was all well over 10^11 ohms at 1kV for every wire to every wire - which is an excellent result. Very happy with that. I made them up at 4 feet at KG's suggestion - that allows the units *not* to be stacked, so helping heat build up.

I didn't watch Life on Mars, but entirely intend to. I only watched the last season of Ashes to Ashes and it was unremittingly excellent, with a really stunning final episode. So let me see - I need to watch two seasons of Mars and two of Ashes - but it is going to be so worth it judging by season 3 of Ashes.

It is the winding connected to the output marked "60V power supply" - that adds -60V to -500 to make -560, and the one marked "300V power supply, that adds 300V to the -560V supply to make -260V. And yes - winding wire is supposed to hold off 500V - but I wouldn't like to rely on it. It might be OK at T=0, but after repeated thermal cycles I would not have confidence that it would hold up long term. It is one of the reasons that transformers with an interwinding screen are often unreliable - the devil is in the detail.

I though - nah, that can't be right - the difference must be significant. I remembered Leslie's Cube from schooldays and foggily recalled a much greater effect. But then I found and scanned "An experimental inquiry into the nature and propagation of heat", By Sir John Leslie, 1804 (Readable on Google books) and noticed that the basic experiment only measures radiant effects - not convective ones. So the experiment is entirely relevant for space based thermal radiators (which would have astonished Leslie), but not ones in air. But then I found the comment relating to normal heatsinks: "Under natural convection conditions, the performance of a heatsink with a black surface will be 6% to 8% better than that with a plain or bright surface. However, this differential disappears under forced air conditions." Significantly less than I had intuitively expected - but consistent with the primary cooling effect being convection. The above comment was on Basic Theory , which seems to be a distillation of heatsink info from several sources.

One additional thing that is worth mentioning to a transformer manufacturer is that some of the windings float at high DC. Specifically the heater windings to the EL34's (-500V), and two of the HT transformer windings are referenced to -560V or -500V. So those windings in particular need an insulation barrier - just overlaying one secondary over another probably won't work (it *should* in principle, because winding wire is good for more than that - but not if any insulation is compromised through nicks during winding, or just thinned because of winding pressure).

Sounds amazing Doug! But beware head brewer syndrome. Mrs S is an accountant, but way back when she was an audit junior she was on the stock check team of a local brewery. She was warned not to approach the head brewer until the afternoon until he had done a good session of "sampling" and was not suffering from the after effects of the previous day's sampling.

FWIW my total Mouser bill was

Oh bloody well done! Nice one.

Looks like an interesting outfit - good luck!

Have they seen the 80's Thomas the Tank Engine TV series with Ringo Starr doing the voice over? Allegedly Starr was using doing the series as part of rehab coming off the booze. Anyway, the early series with Starr were iconic and excellent - my kids were of that pre-school and early school age when it was first aired, and I had great fun watching it with them.

Well, I sure sweated doing the precise same thing in my driveway. Got to a sweltering - well for the UK sweltering - 30C (86F). Hasn't rained for what seems months. English Lake District, which was at the receiving end of near biblical flooding in October 09, is now in an official drought with hosepipe use banned.