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kevin gilmore

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Everything posted by kevin gilmore

  1. kevin gilmore
    Kerry is a bit nervous that the v3 servo for the carbon may not work, so I did a v4 board which has both servo's on it, use one or the other. Much safer for the group buy I think. http://gilmore.chem.northwestern.edu/kgsshvcarbonv4.jpg
  2. kevin gilmore
    those are bipolar inputs, with a bit of offset current, so you really need a 10k input pot, or 10k resistors to ground. other than that I listened to my latest set of boards on the new power supply, and there is definitely a noticeable difference in noise with iem's.
  3. kevin gilmore
    yes, buy a bunch. but it is more money than an open frame ps.
  4. kevin gilmore
    I guess that the next thing I have to master is micro engraving. I do have the tools...
  5. kevin gilmore
    if you do the 2 complementary singles, then yes, otherwise no. also the bom lists the on board pass transistors, not the off board ones I did more testing, and at 500ma, the minimum dropout voltage seems to be closer to 3v. But at 5v, the pass transistors do just fine with a small heatsink as is. 5V, 500ma ... 2.5 watts
  6. kevin gilmore
    not an error. from the krell power supply, 10 ohm resistors from iec input ground to power suppy ground. not likely that anyone including me is going to use it though.
  7. kevin gilmore
    ground down the middle. there is actually a benefit of dual supplies. the noise spikes what little of them exist cancel.
  8. kevin gilmore
    2 watt transformer... no 22 watt, just barely 30 watt transformer is about right one of the mounting holes is 25th off of square. current posted boards (dual and singles) have the mounting holes one size smaller, the silk screen fixed, and 1 resistor each moved by 25th. done measurements this morning in a screen room is about 800picovolts of noise. and voltage stability exceeding 6.5 digit meter. anything better is going to require stupidly expensive test gear.
  9. kevin gilmore
    its a 10 volt reference, the feedback resistors are 1.5k which is a divide by 2. So if you change the top 1.5k resistor you can get any voltage you want. 750 ohms makes it 15v http://gilmore.chem.northwestern.edu/goldenreference.pdf change R8,R9
  10. kevin gilmore
    likely depends on current level, have to bolt to heatsink to test. at 500ma output, looks like about 4V
  11. kevin gilmore
    you can with parts changes including higher voltage rating caps, and opa445's take the output voltage all the way up to +/-60V in which case you need the ratings on those transistors. compared to everything else, the transistors are among the cheapest of the parts.
  12. kevin gilmore
    my unreg primary is 41v, so its way higher than normal. I did attach the biggest U bracket heatsinks I had around (bhse ones) Ran 500ma load. Definitely gets too hot to touch in a few minutes. you do realize this is set for +/-20, so if you want other voltages you have to change the feedback resistors. (+/-20 is my favorite voltage for ssdynalobal)
  13. kevin gilmore
    I'm happy to report that the goldenreference low voltage dual power supply works as designed, and tests less than 1 microvolt of noise. Going to have to take it to work and put it in a screen room to really measure the noise. http://gilmore.chem.northwestern.edu/goldenreferencedual.jpg however there is one silkscreen error seen by the extra + near the 47uf cap on the right side. I will update the files shortly. All 4 of the 47uf caps need to have their plus sides pointing to the left. very happy with this
  14. kevin gilmore
    mine looks a fair bit different, 4 inch long cylindrical thing labeled 5%
  15. kevin gilmore
    unscrew the red barrel on the hv probe and notice the accuracy of the resistor.
  16. kevin gilmore
    this is all about the real impedance of the dmm. Almost all of which are specified as 10M. But when you actually measure them, all over the place. especially if you have over-voltaged the thing a few times. So its a random number generator. The real ultra high impedance meters are expensive, and the high voltage probes are +/-10% it would be nice to get rid of all the zeners in the bias supply with some ultra accurately regulated power supply. it would be much lower noise, but way more complicated. pretty much another hv supply with smaller caps
  17. kevin gilmore
    The test point on the power supply is low impedance! So 580 there is 580 no matter what kind of meter you use. most of the other amps don't have test points, and the only thing you can do is measure at the stax jack which is 4.7M away from a low impedance voltage source. for all of my newer power supplies, the 580v is generated with zener diodes, and is not adjustable like the much older supplies.
  18. kevin gilmore
    absolutely true for safety reasons. AND FOR NO OTHER REASON! but for minimum hum, everything inside the chassis including power supply ground, rca ground, and any ground referenced outputs should float from the chassis. works way better that way.
  19. kevin gilmore
    nope, a standard 10meg input impedance dmm is going to read about 30% to low. the high voltage probes have a 1Gohm impedance, so far more accurate.
  20. kevin gilmore
    fixed the 4.7k resistor and the size of the 5pf caps the accuracy of the resistor is not critical, I picked the standard value.
  21. kevin gilmore
    all board files should be fixed, please check
  22. kevin gilmore
    feel free to stuff whatever you want into whichever hole you desire (paging steve) will have to order a couple of parts from Canada to make sure, unless someone knows of a usa distributor.
  23. kevin gilmore
    while that would work for the unregulated input, for the output, its a bunch more work so I will do the layout with O+,I+ shorted and O-I- shorted all files updated, please check that I hooked everything up to the right place.
  24. kevin gilmore
    if you wire the 4 wire caps the way they want you to wire, the board would have to change a fair bit to use those caps, then you could only use those caps. (board sizes would stay exactly the same) 5 more board types... I can do that... not sure how they would like getting I+ wired to O+ and I- wired to O- if anyone has experience with these caps...
  25. kevin gilmore
    is there any interest in the mundorf 4 wire capacitors? I could change the 4 pin kemet to the 4 pin mundorf, or add the mundorf in addition which might get a bit messy
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