Craig Sawyers

So I understand from KG - so that is what I've done. I think he's updated the PSU schematic to include all this stuff - usual link. Took more than half an hour to find my 1/4" crimp receptacles. Aagh.

Plus the 10k resistor between the voltage reference and pin 2 of the OP27.

Who was that? Dalbani/Nikko or some other one I haven't found yet? That price seems very good. OK - I'll bite - put me down for a set. After all, how many KG designs does a man need? Um, how about a full house.... In the UK Farnell stock them (at least if we're talking Aavid 6300BG), their part number 1213471 at

First things first - welcome back! I've done the mod, board bolted to heasinks, just wiring in the transformers. Hopefully later today this puppy will get fired up.

Um - surface area of Britain (England, Wales and Scotland added together) is 94,000 square miles. The USA is 3,718,000 sqare miles - so you could fit 40 Britains into the US. Texas alone is about three times that of Britain at 262,000 square miles. We're about the same surface area as many individual States (Wyoming, Nebraska, New York etc). Except we have 60,000,000 people crammed in. If you take just England the comparison is even more extreme - England is a truly tichy 50,000 square miles, about the same size as Pennsylvania.

In the UK you cannot drive for that length of time without ending up in the sea (assuming you don't drive in circles) - even Lands End to John'O'Groats. The record for cylcing the 874 miles is not much more than twice the number of hours you drove yesterday - 41 hours. But I've driven many times in the USA, and it is bewildering how long you drive for and hardly make a dent on the country.

Been there, done that, got the badge.

The Exorcist. I'd forgotten what a good film that was, particularly given the trashy horror movies that were around at the same time (1973).

Or even the word processing pool: And the WWII PC:

Interesting - mine are Analog Devices OP27GPZ. Waiting for bolts to strap down the mains transformers, then I'll fire it up into dummy loads.

Does the existence of the wierd shrine increase or decrease your hatred-o-meter?

Visited Cardiff yesterday and today with good friends that have a holiday flat there. Cardiff is where Torchwood and much of Dr Who is filmed. Now if you follow Torchwood, you'll know that a key character called Ianto Jones was killed off in the final series. Now the bizzarest thing I think I have ever seen is that there is a shrine in Cardiff at the place where the (fictional) character was killed. Damnedest thing. Just started by the odd fan, flowers are left and personal messages are pinned up. Lots of pics around, but one link is here Shrine to Ianto Jones and Torchwood | Flickr - Photo Sharing! . I kid you not. Seriously wierd.

Sort of a Greppet. Or a Whiphound Seriously - that is one cute doggie.

You're a really good guy! That little rascal is so cute

That looks real kick ass! I know of someone who, while training for a mountain challenge turned his ankle to the extent it came up like a football. Detemined not to let it get to him, he had a custom brace made to support the ankle and succeeded in hauling his ass over 63 miles. So braces work - we'll look forward to hearing how yours goes (and see some pics when you get it!) The muscle loss thing is a real PITA. I damaged a knee three years ago when I tripped and went flying while running down a mountain (don't ask). After a knee op to extract the floating bits of bust cartelidge, I was appalled by how quickly I lost my quads on the damaged leg - they almost withered before my eyes. Fortunately the op was a real success, so am back to running stupid distances. Maintain balance in the quads in the gym by doing leg raises on a machine with alternate legs. Gone from a 4:1 ratio of strength (really!) to less than 10% difference. So take the loss in muscle tone seriously, and do as much as you comfortably can to correct it. Imbalanced leg strength will tend to cause referred injuries elsewhere (knee, lower spine, hips etc).

Revised transformer currents. The effective secondary resistance is much higher than I though, and that limits the secondary current spikes going into the reservoir caps. On my transformers (remember these are not SumR), the 485V secondary is 71.7 ohms at room temperature, and the primary is 33.5 ohms. The effective 2:1 step up ratio to 485V (from a 240V primary) gives a four times reflected primary resistance into the secondary. So the effective secondary resistance is 71.7 + 4 x 33.5 = 206 ohms. The SumR transformers will give different resistances, but not by a huge percentage I suspect. Running the analysis with that resistance gives 50mA, rectified voltage 647V and secondary current of 108mA at 52VA 75mA, rectified voltage 629V and secondary current of 150mA at 72VA With hot windings and loaded other secondaries the rectified voltages and VA will come down a tad for the 485V winding. So a totally loaded secondary spec for the 485V winding of 130mA is about right. Those numbers are consistent with Kevin's figure of around 630V on the packages of the current sources - hence the need for the ceramic insulators.

Looking at the basic rectifier circuit - there is a secondary feeding a bridge feeding at 430uF cap (two 680u in series). Now it depends on the effective secondary resistance, but I calculate: For 50mA delivered, transformer current = 130mA For 75mA delivered, transformer current = 184mA So possibly the -500V rating is a bit close - but it depends on the detail of the transformer design. With that in mind, might it be worth using the 60V winding on the +500V supply rather than the -500V one? That way the dissipation would be shifted from the more heavily loaded -500V transformer to the +500V one. Inu, bear in mind that most mains transformers, when operating at design ratings run hot - typically 40C surface (and hotter inside) - and too hot to comfortably touch. The only way to avoid this is to massively overrate to keep ohmic and core losses low.

FWIW I twisted my heater wires and then ran them through a high temperature glass fibre braid sleeve (why? I just happened to have a load from a project about 10 years ago). That sub-bundle runs with the other wires inside the usual woven net sleeve. Times two of course as per KG's scheme and chassis mechanics.

I'm really sad that you had such a tough time winning through to fulfil your vision. From here on in it needs not only complete and utter focus, it also needs the cards to fall right. As an example of cards not quite falling right, a very good friend is Shelley Katz (do a google - anything that involves piano is him). He won piano competitions in Canada and internationally from the age of 6 onwards. He is fortunate that he has supportive parents - his mother described to me how 6 year old Shelley was so small that the piano stool slid backwards in a competition - he apparently did not miss a note, and still managed to operate the pedals from a sort of crouch (he won). Onwards to the Juliard, and on the brink of an international concert career, his parents nearly went bankrupt - so Shelley stepped in to help for 6 months. And missed the boat; the phone asking for availability for engagements slowed down and finally just stopped ringing. The cards did just not fall right. Don't get me wrong - he still records, accompanies and performs - but at a modest level of "fame", rather than someone like Murray Parahia. He's also married to Diana, a superb and delightful coloratura soprano, and they perform together quite extensively and internationally. When visiting them (they live in Cambridge UK), I've been lucky enough to get impromptu private recitals, which have always reduced me to tears. Diana performs under her maiden name of Diana Gilchrist (google again..., or MAIN ). Anyway - the watchword is to stick at it 110%, and never ever get de-railed.

You must be pretty damned good - performance standard for sure - if you are heading for the Tchaikovsky. What's your instrument?

I'll not hold my breath then

Not quite sure where to post this. However, I've just been in touch with Linear Systems regarding their replacement to the 2SJ109. They've come back and said "We have plans for this year. Check our website for updates." So it looks at last like the 2SK389/2SJ109 lives again.

Plus the medicinal qualities of gin, zest of lemon and lime on the rocks to take away the taste of the quinine of course

D'you know, I looked at that darned article and totally missed that! Thanks for spotting what I'd not