kevin gilmore

shit, looks like the feedback is upside down again. my simulation software continues to do that. I thought i had it fixed, evidently not. same thing happened to the original squarewave clone. i am changing to new simulation software, probably today. huge learning curve, not happy. will check when i get home, i don't think i have that file here. better idea... remove r19 from the board. solder in 2 x 50k resistors on the bottom of the board from the opamp output pin to the top and bottom of the bias generator. Same as this. http://gilmore.chem.northwestern.edu/multiamp.pdf let me know...

since grindingthud seems to be faster at building and testing my stuff than I am... http://gilmore.chem.northwestern.edu/th.jpg http://gilmore.chem.northwestern.edu/thps.jpg http://gilmore.chem.northwestern.edu/boards/th.zip http://gilmore.chem.northwestern.edu/boards/thps.zip the big high voltage cap is actually 470uf 160v and the little cap is actually 33uf 160v they are right on the boards, wrong on the pictures schematic http://gilmore.chem.northwestern.edu/th.pdf

its bipolar inputs, (one of my pure bipolar series) so there is input offset bias current. Input pot really should be 10k or 20k. very fast, very low noise, very low distortion.

thermal on pin 3 is definitely missing. will fix on the layout in a few minutes. pin 3 has to be connected to ground.

definitely ok on +/-20v

likely ,5 volt in which makes sense, gain of 5

actually everything i did was 3 oz copper, mainly for the filament traces. Also good for higher currents found in ssdynahi etc. and yes i own a metcal now, someone gave me one. hard to go back once you use one for a while. previously i was using a 40 year old weller.

rv3 is the common mode offset pot. with the 2 other pots in the center, and the servo's removed you adjust for minimum between both outputs and ground. then you adjust the other 2, then add the servos

about overkill... if you want 350v out, then the error amplifier really should get 400v from the zener string, which compensates for the hot/cold and then the unregulated input voltage should be 450v and that is right at the limit of a 450v cap. So while 2 caps in series is overkill you can always pick lower voltages and higher capacity, say 2 x 250v caps. Or 1 x 500v cap, and the 500v caps seem to go in and out of stock often. running things with less clearance on the voltages ends up raising the noise level. Still its much less than noise than the simple supply and the amplifier is definitely subject to power supply noise

its all about the size of the box. if you go with a bigger box you certainly can use the more extensive power supply which is far more voltage stable and substantially less noise.

the schematic capture auto numbers stuff, and I never pay any attention to that when I do the board. what I should do is use the netlist, but that is just so much work. the problem happens when you go back and change the schematic, and the board no longer matches... if I actually did this for a living, I might pay more attention. then again, for things like the step attenuator where a schematic never existed in the first place...

i definitely have all the parts. And an unlimited supply of both liquid and gas N2. I even have a pair of oxford standalone N2 gas generators which have never been used. hmmm... what i want is some metal balls with a liquid sodium center, stick in LN2 to get them super cold, then use as long lasting icecubes that can't melt.

each ssdynalobal board pulls about 180ma at 20v

you should ask this question in the megatron thread, but there is a constant current source at the cathodes, and you can't do dual current sources. The current source at the cathode is necessary to keep the differential gain high. you could replace the cathode constant current source with a resistor, then do more of the same current sources as the second stage.

bad input tube usually causes this.

kgst, kgbh,kgbhse,kgdt and T2 all use constant current plate supplys as well as the srx revisited. So the tube tester would need to be modified because the resulting curves would be very diffent.

every direct drive electrostatic amp i know of is balanced. the luminare piece of crap drives the transformer unbalanced only with asymetrical drive, and has very different rise and fall slew rates.

I still have a bottle of some Cuban liquor that my parents brought back from their honeymoon 63 years ago. Still tastes great. If scotch (or any other whiskey) only lasts 6 months, I'm going to have to take the next 2 months off of work and go on a real bender.

board getting there http://gilmore.chem.northwestern.edu/tubehybrid.jpg

the 15 second startup delay is intentional. you can change the resistor string to make it more or less sensitive

test circuit certainly worked, and I don't believe in virtual grounds for all sorts of reasons. when you are running a dynahi with 400ma of bias, 25ma to turn on the relay seems tiny

It appears that the LM339s are powered by V+/V- rather than V+/GND? yes The LM339 has 4 comparators in it. It appears that 2 are being paralleled for each input signal? yes, one for the + limit, the other for the - limit and then repeated 4 times for each of the signals The input protection diodes run from V+/V-? to the inputs of the lm339, not as shown. this should make it easier http://gilmore.chem.northwestern.edu/protector3.jpg

yep. if you match the fets with the transistor tester you can get that 2.2V down to about 100mv but you need a bunch of them, over a 4:1 range on idss done

lots of variation in the fets. i had to hand pick, and throw out a few. the 1.45 volt is not that out of range, i can actually get mine to 160ma. you measuring the 2V without the servo? the servo takes about 30 seconds to bring it to about .1v or less.

this circuit is ground referenced, so not suitable for megatron style stuff. Unfortunately, the only thing that works there is the T2 circuit, or something like it due to having to drive the output tube at -500V was not aware of the other Fairchild parts, definitely in this case better than the higher voltage parts. Really only need 200V parts