kevin gilmore

Tried a number of the C,RC,LRC,.... Which resulted in magic smoke and parts flying across the room. Inductors are a bad bad thing. By the time you are at microvolt levels nothing works. Now if i wanted to double the size of the power supply, i could bandpass filter the noise peaks, invert with an ultra low noise amplifier, and add it back in to the output signal, canceling out the spikes. At which point you would still have about 1 microvolt of thermal and shot noise. The amplifier has 50 to 60db of power supply rejection anyway. Even if you piled up a large stack of car batteries, the resulting noise would be more than 10 microvolts.

So i messed with the imaging NMR for about 4 hours on the block of wood. Proton(high band): Absolutely positively NOTHING. 1 hour of scans at minimum stepsize. Carbon(low band): Maybe even the slightest hint of NOTHING. 3 hours of scans at minimum stepsize. If there is any signal, its buried in the mud. Maybe a few days of scans might generate something. But i really can't do that. Except maybe over christmas or new years. Will try ultrasound on monday. My opinion is that if there was a way to see inside the wood, someone would have already found it and published it.

I'm pretty sure i'm done with the power supply, schematics and board layout updated. Tests indicate about 12 microvolts of noise at full power. Its when the diodes turn on, and using the 35ns soft recovery diodes, even ceramic caps across them make no difference. Over the range 10C to 50C and under full load the power supply voltage changes only 1.2 volts. Measuring this is not at all easy. So i'll call it a better than -140db power supply and be done with. http://gilmore.chem.northwestern.edu/kgsshvpower3.pdf spacers added to the non-insulated parts, update in a few minutes. http://gilmore.chem.northwestern.edu/kgsshvps7c.jpg also dual cap sizes for spritzer, and heatsinks for luvdunhill

one thing i have yet to try is to just add the capacitor, without cutting the land. The impedance of the reference may already be high enough not to need the resistor.

1/4 watt is plenty. 1/8 watt would work too. You can build the 1/8 watt into a pair of sockets. (i'm behind on this)

http://gilmore.chem.northwestern.edu/woodknob3.jpg Tried to xray the wood block. Full power, 50kv @ 50ma. 5 minute exposure. Absolutely nothing. Not even on the part that is 1 inch thick. I did just get funded for a copper microsource which is about 10 times the bang. Maybe one of these days i will sneak it into the APS... Next up Nmr Imaging. (MRI for the rest of you...)

Polishing of the 8 chassis is done, parts will be here monday. Then 4 of them will go for anodizing.

ultrasound huh? I very much doubt it. But i do have access to a newer vintage Siemens unit, will try tomorrow. The stuff is just about as dead as can be, i doubt ultrasound would go thru the wood more than .25 inch. MRI... No way.. But i have a year old bruker imaging system with a 9T magnet, can try that tomorrow too. If it does work, that would be very slick. None of these systems have the resolution that i think would be necessary. At least 100 lines per inch would be needed. I'll walk around tomorrow with my woody and see what i can do.

Yep, that works. Slightly more expensive, but ok. The prices on the cree diodes is just plain silly.

Now i find the stth1512 rectifiers are no longer available in a to220 package, or order time is a year... Need 1200 volt 8 to 15 amp ultra fast rectifiers in a to220 package... In stock...

my xray machines are designed to go ultra small. So even an ic chip is kind of big. i know where to take it to do a standard film xray, will have to try it. Don't think the resolution of film is going to work on this.

If i had any idea the eye was inside the piece of wood like that, i certainly would have done so. There was no way of telling from the outside what the pattern on the inside was.

http://gilmore.chem.northwestern.edu/woodknob2.jpg This is completely unpolished. 45 minutes with a carbide point. Took .01 of the top too.

more better yet. http://gilmore.chem.northwestern.edu/kgsshvps7c.jpg no expensive crd's, the 10m90s works just fine. small heatsinks probably not necessary, but there is room for it. noise and ripple about 200 microvolts peak to peak with full load.

http://shop.hoodiebuddie.com/ there was a vendor trying to sell these things on campus...

screwdriver and hammer... first seperate from the basket. but they are more fun if you leave the pole pieces on, the magnetic field at the center is much stronger that way.

current version of board, luvdunhill wanted heatsinks on the +/-15 to power something http://gilmore.chem.northwestern.edu/kgsshvps7a.jpg will add the crd's once i test that it works as i believe it will.

Decca ribbon tweeters. Element resistance, 25 milliohms. Driver transformer 100:1 .5 inch wide strip of aluminum about 4 inches long. 10 mill thick. Have a pair, have not played with them in quite some time.

That is not oscillation, that is the charge/discharge of the main caps. What you have to do is remove the other traces and expand the green. Also look at the drive voltage on the base of the reg transistor. Sure looks like it works right to me. Fact is this power supply design is at the -100db level for noise/ripple. Not easy to do for high voltages. John curl has enough of a hard time doing that for +/-30v. Also that version of the voltage doubler might be more than 900 volts which is a bit much for the ixys part. This is exactly what i want, a discussion of design by informed people. Doing the circuit boards is the easy part. 2.6K load resistor?? Thats quite high in power...

Yep, works for the BH, but you are wasting a bit of power because the unregulated rail needs to be 600 volts to make the bias source work. Now if you want to get really silly you can replace R1/R28 with a 1ma CRD (in parallel with a 100v zener to protect it on turn on) and get the ripple down into the 50 microvolt range. I have not tried this yet, but i have ordered the diodes.

There is a reason stax always used red led's. led's don't share current well, so putting them in parallel, usually does not work.

Had to be at least 20 takes and a massive edit job. No way even those professionals could do that in one shot.

like this http://gilmore.chem.northwestern.edu/kgsshvpower3.pdf The 4 pass fets are all isolated case... Same thing with the 2sc4686a Sure would be nice to come up with an isolated version of something for the bias supply. It would make assembly idiot proof. You can of course go nuts on the 10 volt reference chip, some of the linear technology chips are 10 times better, and 20 times the cost. Problem is distributor availability on those. The issues with the zeners is absolutely real. This is why the KGBH supply, and the cavalli supplies drift a few percent over temperature. The KGBH supply is still absolutely the best for AC noise rejection, but i want something that is better than a 1% line/load supply.

This is the power supply i'm planning on going with http://gilmore.chem.northwestern.edu/kgsshvps3.jpg it uses the active battery from the T2 as the regulator. And is adjustable for exact voltages. It is the most efficient (least amount of excess heat) of the 3 supplies. (2 watts vs 5 watts vs 9 watts) And it spreads the pass transistor heat on 2 heatsinks. It is almost as good for regulation over temperature as the T2 supply. (.2% vs .05%) and very low in noise. (about 5mv peak to peak for 1% AC input ripple) It should come about the same money. Schematic later.

Some of the solders i use are older than i am. Never had a problem.