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kevin gilmore

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Everything posted by kevin gilmore

  1. 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
  2. kevin gilmore
    likely depends on current level, have to bolt to heatsink to test. at 500ma output, looks like about 4V
  3. 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.
  4. 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)
  5. 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
  6. kevin gilmore
    mine looks a fair bit different, 4 inch long cylindrical thing labeled 5%
  7. kevin gilmore
    unscrew the red barrel on the hv probe and notice the accuracy of the resistor.
  8. 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
  9. 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.
  10. 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.
  11. 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.
  12. 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.
  13. kevin gilmore
    all board files should be fixed, please check
  14. 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.
  15. 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.
  16. 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...
  17. 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
  18. kevin gilmore
    there have been updates in the boards to replace the 1 x 300k or 510k resistor with 2 x cmf60 resistors. although there is conflicting information from Vishay with 2 documents saying different specs for the cmf60. I think that in any case, the 2 x cmf60 has to work because the total power is 1 watt and the total maximum voltage is 550v someone have a different idea, I can certainly do that. the pdf I am going by is this http://www.mouser.com/ds/2/427/cmfind-239942.pdf the conflicting document is this http://www.vishay.com/docs/31027/CMFMIL.pdf
  19. kevin gilmore
    pcbnet actually has the large board runs made in china. only the rapid response stuff is made in Illinois quality is very good however, the T2 boards were made by them (my production)
  20. kevin gilmore
    the 1k resistor in series with the 2 x 11k resistors. change to 500 ohms and I never liked virtual ground anything. just a bad idea.
  21. kevin gilmore
    the problem with the e12 is the common summing. so even if you do 2 boards, and one hot output is +2v and the other hot output is -2v, the result is zero. if you think that can't happen with some of these whacky dacs, think again you really do need a pair of comparators on each of the 4 lines
  22. kevin gilmore
    you can change one resistor and the setpoint will be .25v or anything else you want. the e12 does not protect against dc offsets at the imput causing differential output voltage that can be significant but adds up to zero and then won't trip the relay
  23. kevin gilmore
    updated picture
  24. kevin gilmore
    http://www.mouser.com/ProductDetail/Phoenix-Contact/1902547/?qs=sGAEpiMZZMvZTcaMAxB2AKJ8wpDgQJg5WwkpmYrVFB4%3d
  25. kevin gilmore
    and then you have to change the driver power supply to +/-350
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